CHAPTER I

GENERAL PRINCIPLES OF VETERINARY PHARMACOLOGY

1. INTRODUCTION TO VETERINARY PHARMACOLOGY

Importance and relevance of studying Pharmacology:

1. Understand drugs and how they can affect living things

2. Know the right dosage of drugs and just quantity
3. Identify and respond to drug interactions, reactions and side effects and treat accordingly
4. Know when to use drugs because some conditions do not need drug therapy
5. Understand the process of drug intake, absorption, distribution, metabolism and elimination
6. Identify the properties of ideal drugs and otherwise
7. Know the application of pharmacology in veterinary medicine with regards to the 5 rights of:
• Use of right drug
• Give to right patient
• Give right dose
• Give by right route
• Give at a right time

WHAT IS PHARMACOLOGY?

Etymology: Pharmacon = drug; Logos = study

1. Science of drugs and their interaction with living organism.

2. Study of the properties of drugs and all aspects of their interaction with living organisms.
3. Study of properties of drugs and their effects on the structural and metabolism of normal tissue.
4. Study of substances that interact with living system through chemical processes, especially by binding
to regulatory molecules and activating or inhibiting normal body processes.

Pharmacology includes:

1. Pharmacokinetics: the study of the characteristics of the time course and extent of drug exposure in
individuals and populations and deals with the absorption, distribution, metabolism and excretion
(ADME) of drugs. It has been described as “what the body does to the drug.”
2. Pharmocodynamics: is the study of the biochemical and physiological effects of drugs, their modes
of action and the relationship between drug concentration and effect. It has been described as ‘what
the drug does to the body’. An understanding of pharmacodynamics forms the foundation of rational
therapeutic drug use and provides insights into improved dosage regimens and possible drug
interactions as well as the design of new drugs.
3. Toxicology: is the branch of pharmacology that deals with the undesirable effects of chemicals on
living systems, from individual cells to humans to complex ecosystems; study of poisons, including
their chemical properties and biological effects
4. Pharmacotherapeutics: refers to the application of drugs for use in the diagnosis, prevention, and
treatment of diseases, induction of anesthesia and synchronization of uterus in farm animals. It
includes drug of choice,, route of administration, forms of drugs and frequency of administration.
5. Pharmacy: the art and science of preparing, compounding and dispensing of drugs
a. Pharmacognosy: study of source of drugs; study of medicinal drugs obtained from plants or
other natural sources
b. Posology: study of drug dosage
c. Metrology: deals with weight and masses as applied to preparation and administration of drugs
• Dose: quantity of medicine to the administered at one time; amount of drug received per
animal.
• Dosage: amount of drug per unit of animal mass of weight; can also be expressed as the
amount ofdrug per unit of mass or weight per unit of time (example, 50 mg/kg/day for one
week)

Categories of Pharmacology

1. Molecular Pharmacology: concerned with the study of basic mechanism of drug action in biological
system aims to determine and interpret the relationship between biologic activity and the structure of
molecules or group of molecules .
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2. Clinical Pharmacology: concerned with the rational development, effective use,and then proper
evaluation of drugs for the diagnosis, prevention and care of diseases also deals with the safe use of
drugs in any animal species including human being; devoted to the study of the clinical effects of drugs on
patients with a goal of optimizing therapeutic dosage regimens.

Clinical pharmacology in the veterinary setting is the clinical discipline devoted to the optimal use of drugs
in veterinary patients, maximizing their prophylactic or therapeutic benefi ts while ensuring that the
adverse consequences of drug use are minimized.
3. Veterinary Pharmacology: concerned with drugs as they are used in the diagnosis and treatment of
animal disease, and in the intention alteration of animal physiology. The range of animal species in which
drugs are used and studied distinguishes Veterinary Pharmacology from, medical (human) Pharmacology
4. Pharmacogenomics: the relation of the individual’s genetic makeup to his or her response to specific
drugs

2. A BRIEF HISTORY OF PHARMACOLOGY INCLUDING ITS VETERINARY ASPECTS

Since the dawn of humankind, mixtures of animal parts, plants and minerals to treat wounds, sores
and ailments evolved from rudimentary pharmacological compounds into more sophisticated experiments to
create medical treatments. Egypt first documented herbal amalgams for healing. Archives of ancient Greek
texts reveal the extent of their medicinal knowledge of herbal mixtures. Chinese and Arab peoples advanced
pharmacology research of herbal and mineral benefits for medical treatments as well. Early in the 20th
century, modern pharmacology emerged with the first synthetic compound created in Europe.

Prehistoric: Knowledge of pharmacology practiced by humans before the Egyptian and Greek writings
comes from archaeological findings. Because prehistoric humans had no understanding of the inner workings
of the human body, pharmacology was a rational application of what they could see. These early people
treated wounds, burns and broken bones with plants and locally gathered materials to assist in the healing.

The Medical Book of Thoth: Ancient Egyptian life evolved around their many gods. Thoth, the
Egyptian Goddess of knowledge, left 42 books directing how Egyptians should live. Among these records, one
specifically provides cures from plant and animal mixtures for human ailments. Court records from Egypt's
18th Dynasty (1550 to 1292 B.C.E.) are the first known reference to this tome.

Ebers Papyrus: The Ebers papyrus, the world's oldest preserved medical and pharmacological
record, is believed to be a copy of the book of Thoth. It measures nearly 20.23 m in length and 30 cm in
height. The 110-page scroll from 1552 B.C.E. contains 700 medical and pharmacological recipes for
treatments from crocodile bites to intestinal afflictions as well as diabetes and arthritis.

China: Shen Nong recorded hundreds of Chinese medicinal herbs over 4,000 years ago. Included in
China's Shen Nong's "The Divine Farmer's Herb-Root Classic" are 365 medicine compounds made from
minerals, plants and animals. Shen Nong personally tested the properties of hundreds of medical herbs he
identified around 2000 B.C.E. His experiments and documentation are the forerunner to the development of
traditional Chinese (herbal) medicine still used today.

Arabic Pharmacology: The first pharmacological medicine written in Arabic provided formulas
organized by preparation--powders, tablets, ointments and syrups. This work, written by al-Agrabadhin tly
Sabur bin Sahl in 869 C.E. provides recipes with methods and techniques to create pharmacological
preparations along with the dosages.

Modern Pharmacology

Pharmacology is one of the cornerstones of the drug discovery process. The main tasks of
pharmacologists in the search for and development of new medicines are:
• screening for desired activity,
• determining mode of action, and
• quantifying drug activity when chemical methods are not available.

Synthetic organic chemistry was born in 1828, when Friedrich Wohler synthesized urea from inorganic
substances and thus demolished the vital force theory.

The birth date of pharmacology is not as clear-cut. In the early 19th century, physiologists performed
many pharmacologic studies. Thus, François Magendie studied the action of nux vomica (a strychnine-
containing plant drug) on dogs, and showed that the spinal cord was the site of its convulsant action. His work
was presented to the Paris Academy in 1809.
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 In 1842, Claude Bernard discovered that the arrow poison curare acts at the neuromuscular junction
to interrupt the stimulation of muscle by nerve impulses.

Nevertheless, pharmacology is held to have emerged as a separate science only when the first
university chair was established.

According to Walter Sneader, this occurred in 1847, when Rudolf Buchheim was appointed professor
of pharmacology at the University of Dorpat in Estonia (then a part of Russia).

Lacking outside funding, Buchheim built a laboratory at his own expense in the basement of his
home. Although Buchheim is credited with turning the purely descriptive and empirical study of medicines into
an experimental science, his reputation is overshadowed by that of his student, Oswald Schmiedeberg.

Oswald Schmiedeberg (1838–1921) is generally recognized as the founder of modern pharmacology.

The son of a Latvian forester, Schmiedeberg obtained his medical doctorate in 1866 with a thesis on the
measurement of chloroform in blood. He worked at Dorpat under Buchheim, succeeding him in 1869.

In 1872, he became professor of pharmacology at the University of Strassburg, receiving generous

government support in the form of a magnificent institute of pharmacology. He studied the pharmacology of
chloroform and chloral hydrate.

In 1869, Schmiedeberg showed that muscarine evoked the same effect on the heart as electrical
stimulation of the vagus nerve. In 1878, he published a classic text, Outline of Pharmacology, and in 1885, he
introduced urethane as a hypnotic.

In his 46 years at Strassburg, Schmiedeberg trained most of the men who became professors at other
German universities and in several foreign countries. He was largely responsible for the preeminence of the
German pharmaceutical industry up to World War II.

In the United States, the first chair in pharmacology was established at the University of Michigan in
1890 under John Jacob Abel, an American who had trained under Schmiedeberg.

In 1893, Abel went to Johns Hopkins University in Baltimore, where he had a long and brilliant career.
His major accomplishments include the isolation of epinephrine from adrenal gland extracts (1897–1898),
isolation of histamine from pituitary extract (1919), and preparation of pure crystalline insulin (1926).

His student Reid Hunt discovered acetylcholine in adrenal extracts in 1906.

Today, there is a pharmacology department in colleges offering medical courses (i.e, human
medicine, veterinary medicine, dental medicine, nursing, pharmacy)

The Use of Animal Studies

Pharmacology depends largely on experiments conducted in laboratory animals, but even the human
animal may be used as a test subject.

Friedrich Serturner, the German pharmacist who isolated the first alkaloid from opium in 1805,
administered a whopping dose (100 mg) to himself and three friends. All experienced the symptoms of severe
opium poisoning for several days. The alkaloid was named morphine, for Morpheus, the Greek god of sleep.

An interesting example of the use of humans for testing occurred in the 1940s. Although digitalis had
been a standard medication for heart disease for more than a century, there were still no reliable methods for
evaluating its potency. Biological assays (bioassays) were performed on frogs, pigeons, and cats, but none
were totally satisfactory.

In 1942, a group of cardiologists published “a method for bioassay of digitalis in humans”. The assay
was based on quantitative changes in the electrocardiogram (ECG) of patients in the cardiac clinics of two
New York City hospitals. It was hard to find patients whose ECGs could be standardized. Of 97 patients in
whom calibration of the ECG was tried, only 18 proved to be satisfactory assay subjects. Fortunately,
chemical research on the active glycosides of digitalis, and development of analytical methods, soon rendered
all digitalis bioassays obsolete.

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 Although humans are no longer used as ad hoc laboratory animals, they are essential in clinical
pharmacology.

When a new drug compound has gone through sufficient preclinical testing to show potential
therapeutic action and reasonable safety on short-term administration, and the data have been reviewed by
the FDA, the compound is administered to a small number of human volunteers under closely controlled and
monitored conditions.

These Phase I clinical trials provide information about dosage and the most common side effects to
be expected. The animals most frequently used in pharmacologic studies are mammals. Mice are preferred
because of their small size, ease of breeding, and short generation time. Rats, guinea pigs, rabbits, and dogs
are also used; each has special characteristics that make it optimal for certain types of tests.

Early in the development of pharmacologic techniques, it was found that an isolated organ or tissue
remained functional for several hours in a bath containing a physiologic solution of salts through which oxygen
was bubbled.

Henrick Magnus (1802–1870) first applied this method to a strip of small intestine, Jean-François
Heymans (1904) worked with the mammalian heart, and Claude Bernard experimented with isolated nerve–
muscle preparations.

The organ or tissue is so suspended that the contraction or relaxation of the muscle is mechanically
transmitted to a stylet. The stylet writes on a drum covered with smoked paper rotated by clockwork at a
constant speed. This device, called a kymograph, graphically records motion or pressure. The effects of drug
substances added to the bath can thus be visualized. The kymograph is a relatively crude device. In modern
laboratories, organ and tissue movements are transmitted by force transducers to polygraph machines, which
produce similar tracings. Or the polygraph is replaced by computerized equipment that issues a digital record.

The surgical preparation of animals is illustrated by the following examples. As early as 1849, the
German anatomist Arnold Berthold transplanted testicular tissue into a capon (a castrated rooster) and
showed that this induced growth of the comb. This basic method was used in the 20th century to isolate and
study the male sex hormones.

Similarly, in 1924, Americans Edgar Allen and Edward Doisy used ovariectomized rats to test the
action of estrogenic hormones. To study anti-inflammatory agents, rats can be made arthritic by injection of an
oily suspension of killed bacteria (Freund’s adjuvant).

Drugs affecting gastric secretion may be studied in animals by forming a Heidenhain pouch—a small
sac of the stomach, vagally denervated and closed off from the main cavity, but with an opening through the
abdominal wall.

The Use of Rational Design

Screening of candidate compounds and mode-of-action studies may focus on specific tissues,
organs, or systems or on actions, such as antihistaminic or anticonvulsant.

As knowledge of human biochemistry and molecular biology advances, pharmacology zeroes in more
often on enzymatic action and receptors.

Captopril (Capoten), developed by M. Ondetti and co-workers at Squibb in the 1970s, exemplifies a
molecule that was rationally designed to fit the active site of an enzyme—angiotensin converting enzyme
(ACE). This drug, and subsequent ACE inhibitors, reduces blood pressure.

Knowledge of cell receptors is now on the cutting edge of pharmacology and drug discovery. The
concept was first proposed about a hundred years ago by Paul Ehrlich, the great bacteriologist and chemist
who synthesized salvarsan (also known as “606”) for the treatment of syphilis.

On the basis of his research on bacterial toxins, Ehrlich postulated that the body’s cells possess a
great many “receptors” by which they combine with the food substances in the body fluids. He theorized that
the metabolic products of certain bacteria combine with the receptors of some cells, thus injuring the cells.
Ehrlich visualized receptors as unsatisfied chemical side chains.

This is not far from the modern idea of receptors as domains in enzymes or other proteins, with which
drugs of appropriate structure can combine.
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 Illustrating the importance of receptor research are drugs that act on the adrenergic (sympathetic)
nervous system. This system has both - and -receptors. Propranolol (Inderal) was the first specific -
adrenergic receptor blocking agent. Marketed in 1964, it ended a long drought in new heart medicines and
soon became a major therapy for angina pectoris, cardiac arrhythmias, hypertension, and essential tremor.
However, all -adrenergic receptors are not identical, and propranolol is nonselective.

Second-generation drugs such as atenolol (Tenormin) and metoprolol (Lopressor), developed in the
late 1970s, have a preferential effect on l receptors, which are chiefly located in heart muscle. At higher
doses, they also inhibit 2 receptors, which are found mainly in the bronchial and vascular musculature.

There are also blockers of the -adrenoreceptors, such as prazosin (Minipress; early 1980s), and
1-blockers, such as terazosin (Hytrin; 1987). And there are / -blockers: Labetolol (Normodyne) and
carvedilol (Coreg), developed in the mid-1990s, exhibit selective 1 and non-selective -blocking action.

The methods and approaches mentioned are merely a sampling. Pharmacology is similar to medicinal
chemistry in that it has developed a vast array of techniques, both general and specialized.

Building on its past, the ongoing progress of pharmacology supports its critical role in modern drug
discovery and augurs (predicts) well for the future.

Further developments for veterinary pharmacology may include:

• Further advances in computer technology
• Microfluidics
• Nanotechnology
• High-throughput screening
• Increased control and targeting of drug delivery
• Increased knowledge of pharmacogenomics

Notable people/writings that contributed to the development of Pharmacology

PEOPLE/WRITINGS CONTRIBUTION TO PHARMACOLOGY

Earliest written compilation of drugs, which was written by
PEN TSAO
Emperor Shen Nung in about 2,700 B.C.
CODE OF HAMMURABI
Describe penalties for malpractices of practitioner
KAHUN PAPYRUS (1800 BC) Oldest record of Egyptian drugs
EBERS PAPYRUS (1550 BC) Complication of disease conditions and prescriptions
(ayus-life; veda-science) system of traditional medicine native to
AYURVEDA (4000-600 BC)
Indian subcontinent
ASHURBANIPAL Assembled the library of clay tablets in Sumeria
Greatest teacher of medicine
HIPPOCRATES (460-370 BC)
– “father of medicine”
RENATUS VEGETIUS (450-500 AD) “Father of Veterinary Medicine”
VIS MEDICATRIX NATURAE Concept of the healing power of nature
Formed the scientific basis of medicine, authored History of
ARISTOTLE (384-322 BC)
Animal
Systematically classified medicinal plants
THEOPHRASTUS (371-287 BC)
“father of pharmacognosy”
Established the modern scientific method of naming plants of
CAROLUS LINNAEUS animals
“father of taxonomy”
PEDANIUS DIOSCORIDES (30-90 AD) Compiled d the 1st material medica
Deals with physiology and materia medica
CLAUDIUS GALEN (131-200 AD) • Preparation consisting primarily herbal/vegetable matter

PUBLIUS VEGETIUS Complied a treatise that included prescriptions for farm animal
GEBER IBN HAJAR (702-765 AD) An influential Persian who classified drugs and poisons
MUHAMMAD IBN ZAKARIYA AL-RAZI Introduced the use of mercurial ointments and developed
(865-925 AD) mortars, flasks, spatulas and phials
MATHIEU JOSEPH BONAVENTURE
Published “Toxicologie Generale”
ORFILA (1787–1853)
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JOHN GAMGEE Published “The Veterinarians Vade Mecum”
KENELM WINSLOW Authored “Veterinary Material Medica and Therapeutics”
VALERIUS CORDUS(1514-1544 AD) Compiled the 1st pharmacopeia; pioneered the synthesis of ether
Discovered the circulation of blood and indicated that drugs were
WILLIAM HARVEY
distributed to various parts of the body by this means
CHRISTOPHER WREN 1630, make the 1st I.V. of drug into a dog (opium)
ALEXANDER WOOD 1850, devised the 1st hypodermic needle and syringe
HINDS, HAWTHORNE, WILLERSON Studied hemodynamics of dobutamine in dog
THEOPRASTUS BOMBASTUS VON Introduced the clinical uses of opium or laudanum; also called
HOHENHEIM himself Phillipus Aureolus Paracelsus or just Paracelsus
Isolated the narcotic substance from opium and called it
morphine, after Morpheus
• Nyx – goddess of night, mother of Hypnos
• Thanatos – god of death, brother of Hypnos
• Hypnos/Sommus – goddess of sleep
FREDRICH SERTURNER (1783-1841)
• Live in a dark cave, where the river Lether flowed
through, known as the
– River of forgetfulness
• Morpheus – one of the hundred sons of Hypnos, god of
dream
EDWARD JENER Discovered the vaccine against small pox
First to prove that chemical can be absorbed into the vascular
system
FRANCOIS MAGENDIE
• Established the foundation for modern pharmacology
(drug action, d-12relationship, drug disposition)
FRANÇOIS MAGENDIE AND PIERRE
Made I.V injection of ipecac, morphine and strychnine
JOSEPH PELLETIER (1788-1842)
WILLIAM WITHERING Observed the use of foxglove in the Tx of dropsy
Showed the active ingredient of foxglove and called it digitalis
CLAUDE BERNARD
• Demonstrated that curare prevent muscle contractio
Studied evidence-based pharmacology, which requires that
chemical be term a drug only if the specific action in living tissue
is demonstrated
RUDOLF BUCHHEIM
• Established the 1st independent laboratory devoted
exclusively to the study of pharmacology
• “Father of Pharmacology”
“Father of pharmacology in U.S.”
JOHN ABEL • Isolated adrenalin
• Prepared and crystallized insulin
“Father of Modern Veterinary Pharmacology”
L. MEYER JONES (1913-2002 ) Authored the 1st edition of Veterinary Pharmacology &
Therapeutics in 1954
JESUIT PRIEST Use bark of cinchona tree for treatment of malaria
The term pharmacology (pharmakologie) was applied to the study
of material medica by Dale
HENRY HALLETT DALE
Report that prevent hemodynamic effect of epinephrine
Led in establishing pharmacology as an independent science
OSWALD SCHMIEDEBERG based on experimental methodology
“Father of modern pharmacology”
Pioneer in the field of experimental pharmacology of indigenous
COL.SIR RAM NATH CHOPRA plants of India
“Father of Indian Pharmacology”
1910, reported the synthesis of arsphenamine which in an anti-
syphilitic drug
– Anti-trypanosomal drug
PAUL EHRLICH
– 1st antibacterial drug processing specific it for
invading pathogens
– “father of chemotherapy”
ALEXANDER FLEMING 1928, isolated penicillin
GERHARD DOMAGK 1935, isolated estrogenic activity
RAYMOND P. AHLQUIST Designated adrenergic receptors
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 Placed neuromuscular blocking agent (muscle relaxant into 2
DANIEL BOVET
categories)
DANIEL BOVET AND ANNE-MARIE
Demonstrated 2 types of antihistamine activity (H1 and H2)
STAUB
GILES MERKEL AND EDMOND I Described the standard index of anesthetic potency for inhalant
EGER II anesthetics
ADOLPH VON BAEYER Synthesized barbituric acid
MAURICE M. RAPPORT Isolated serotonin
Characterized the first 4 cardinal signs of inflammation (heat, red,
AULUS CORNELIUS CELSUS
swell, pain)
RUDOLF VIRCHOW Added the 5th sign (loss of function)
FELIX HOFFMAN Synthesize acetyl ester of salicyclic acid (aspirin)
EDGAR ALLEN 1st to determined estrogenic activity
EDWARD ADELBERT DOISY AND
ADOLF FRIEDRICH JOHANN Isolated estrone from female urine
BUTENANDT
ADOLF FRIEDRICH JOHANN
BUTENANDT, (MARCH 24, 1903 - Isolated aldosterone from male urine
JANUARY 18, 1995)
KARL HEINRICH SLOTTA Discovered the steroid structure of progesterone
EDWARD CALVIN KENDALL (MARCH
Isolated thyroxine
8, 1886 – MAY 4, 1972)
MARIA C. R. HARRINGTON Established the chemical structure of thyroxine
OSKAR MINKOWSKI AND JOSEF
Produced diabetes by total pancreatectomy in dog
VON MERING
FREDERICK BANTING AND Extracted the active compound from pancreas and able to control
CHARLES BEST hyperglycemia in dog and human
JOHN JACOB ABEL Prepared and crystallized insulin
FREDERICK SANGER Sequenced the amino acid of insulin
1968, a pioneer of veterinary pharmacology, was elected to a
personal chair in veterinary pharmacology at Edinburgh
FRANK ALEXANDER University, he delivered an inaugural lecture entitled: ‘Materia
Medica to veterinary pharmacology: a transition’ (Alexander,
1969)
MEYENHOFER AND KATSOYANNIS Synthesized insulin
Discovered that insulin was synthesize as a larger molecule
DONALD F. STEINER
called preproinsulin
KIMBALL AND MURLIN Postulated a pancreatic hyperglycemic hormone
A. STAUB Succeed in purifying glucagon
WILLIAM W. BROMER Sequenced the amino acid of glucagon
GIROLAMO FRACASTORO Postulated that germ caused infection
ANTONIE VAN LEEUWENHOEK Discovered microorganism through lenses
Introduced the scientific approach to the field of medical
ROBERT KOCH
microbiology
LOUIS PASTEUR Indentified infective agent as caused of diseases
Demonstrated the beneficial effect of hand washing between
patients
IGNAZ SEMMELWEIS
• Demonstrated antiseptic effect of chlorine (chlorinated
lime)
Suggested the used of antiseptic in the field of surgery
• Used carbolic lotion
JOSEPH LISTER
• Initiated chemical sterilization of bandage, dressing and
surgical instruments
HENRY DRYSDALE DAKIN (12 Introduced chlorine - containing solution (sodium hypochlorite) for
MARCH 1880 – 10 FEBRUARY 1952) disinfecting
WILLIAM CAMPBELL AND SATOSHI Discovered avermectin; 2015 Nobel Prize in Physiology or
OMURA Medicine

Notable contribution of Filipino scientists/group of researchers in Pharmacology

• Dr. Abelardo Aguilar – discovered erythromycin (brand name: Ilosone) in 1949 in Iloilo
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 • Dr. Lourdes Jansuy Cruz – discovered conotoxins (or toxins) from marine snails during the 1970s to
80s
• Lagundi cough medicine – launched in the market in 1994, developed by the National Integrated
Research Program on Medicinal Plants, Philippines (NIRPROMP of UPManila) and Philippine Council
for Health Research and Development
• Dr. Teodulo M. Topacio, Jr. (Doctor of Veterinary Medicine); National Scientist for Veterinary Medicine
2009; helped in the development of antibacterial regimen for leptospirosis among domesticated
animals (with an important discovery that pigs could also be infected with leptospirosis and could then
infect humans)
• Anti-Dengue Drug –Phase 1 Preclinical Testing in 2019, Pharmalytics and De La Salle Medical and
Health Sciences Institute
• Tulkas Lunas Program of DOST

Philippine Laws on Drugs and Medicines

• REPUBLIC ACT No. 6675 “Generics Act of 1988”

• REPUBLIC ACT No. 8423 “Traditional and Alternative Medicine Act (TAMA) of 1997”
• REPUBLIC ACT No. 9502 Amending RA8293, RA6675, RA5921 “Universally Accessible Cheaper
and Quality Medicines Act of 2008"
• Republic Act 9711 also known as "Food and Drug Administration (FDA) Act of 2009

3. PHARMACOGNOSY

WHAT IS DRUG?

Etymology: Droque French word = Herb

1. In a broad sense, is any chemical agent other than food that affects living organisms
2. Any substance which is capable of modifying a biological activity
3. Includes any chemical agent (other than food) used in the treatment, cure, prevention or diagnosis of
disease or the control of physiological processes.
4. Definition from R.A. 9502 Universally Accessible Cheaper and Quality Medicines Act of 2008:

Drugs and medicines refers to any chemical compound or biological substance, other than food,
intended for use in the treatment, prevention or diagnosis of disease in humans or animals, including
but not limited to:
(1) any article recognized in the official United States Pharmacopoeia-National Formulary
(USP-NF), official Homeopathic Pharmacopoeia of the United States, Philippine
Pharmacopoeia, Philippine National Drug Formulary, British Pharmacopoeia, European
Pharmacopoeia, Japanese Pharmacopoeia, Indian Pharmacopoeia, any national
compendium or any supplement to any of them;

(2) any article intended for use in the diagnosis, cure, mitigation, treatment, or prevention of
disease in humans or animals;

(3) any article other than food intended to affect the structure or any function of the human
body or animals;
(4) any article intended for use as a component of any articles specified in clauses (1), (2),
and (3) not including devices or their components, parts, or accessories; and

(5) herbal and/or traditional drugs which are articles of plant or animal origin used in folk
medicine which are:
(i) recognized in the Philippine National Drug Formulary;
(ii) intended for use in the treatment or cure or mitigation of disease symptoms, injury
or body defects in humans;
(iii) other than food, intended to affect the structure or any function of the human
body;
(iv) in finished or ready-to-use dosage form; and
(v) intended for use as a component of any of the articles specified in clauses (i), (ii),
(iii), and (iv);

What are extra-label drugs, compounded drugs, and generic drugs?

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 • New animal drug (NAD): “any drug intended for use in animals other than man, not generally
recognized as safe and effective for the use under the conditions prescribed, recommended, or
suggested in the labeling of the drug.”
• Extra-label drug: when the drug is used in a manner not in accordance with approved label
directions
• Compounded preparation/drugs: constitutes extra-label drug use; undergoes no regulatory
assessment or approval; includes any manipulation of the drug beyond that stipulated on the label
• Generic products/drugs (nonproprietary) drugs that contain the same active ingredient as the
proprietary drug and also meet bioequivalence standards; can be dispensed by the pharmacist

What are prescription drugs?

Drug product or medicine is the finished form that contains the active ingredient (s) generally, but not
in association with inactive ingredients.
• Prescription or ethical drugs are pharmaceutical products or drug preparations that are to be
dispensed only upon written order of a validly registered licensed physicians, dentist or
veterinarian for the management or treatment of a condition disease.
• Non-prescription or over-the counter drugs are pharmaceutical products or drug preparations
that can be dispensed even without the written order of a validly-registered licensed physician,
dentist, or veterinarian, for the use of consumer for the prevention of symptomatic relief of minor
or self-limiting ailments.

What are dangerous drugs?

Dangerous drugs refer to either prohibited drugs or regulated drugs which require a special prescription
form, the use of which is monitored by the Dangerous Drug Board.
• Prohibited drugs include “Opium and its active components and derivatives such as heroin and
morphine; coca leaf and its derivatives, principally cocaine, alpha and beta Eucaine,
hallucinogenic drugs such as mescaline, lysergic acid diethylamide (LSD) and other substances
producing similar effects; Indian hemp and its derivatives; all preparation made derivatives; all
preparation made from any of the foregoing; and other drugs, whether natural or synthetic, with
the physiological effects of a narcotic drug.”
• Regulated drugs includes sleep-inducing sedatives, such as secorbarbital, phenobarbital,
barbital, amobarbital and other drugs which contain a salt or derivative of a salt of barbituric acid;
any salt, isomer or salt of an isomer, of amphetamine such as benzedrine or dexedrine, or any
drug which produces a pharmacological action similar to amphetamine; and hypnotic drugs such
as methaqualone, or any other compound producing similar pharmacologic effects.

SOURCES OF DRUGS

Most drugs currently used in veterinary practice are synthesized by the organic chemist, screened
and tested by pharmacologist and toxicologist, prepared in suitable dosage forms by the pharmaceutical
chemist, evaluated by the clinical investigator, and marketed by pharmaceutical company

• Mineral source:
• Antacids - Magnesium oxide (ex. MAALOX Antacid)
• Purgatives - Magnesium sulfate
• Hematinics - Ferrous sulfate
• Electrolyte - Sodium Chloride

• Animal source: Epinephrine, heparin, insulin, thyroid extract, gonadotrophins

• Plant source (important source of drugs)

• Alkaloids: name end in “ine”; formed water soluble salts
• Alkaloids are precipitated by salts of heavy metals, iodine, and tannic acid. It is important to
know to avoid incompatibilities in drug mixtures and for treatment of alkaloid toxicosis
• Tannic acid precipitate alkaloid thus reducing or preventing absorption from the GIT
e.g. Morphine, atropine, pilocarpine, strychnine, eucalyptus oil, peppermint oil
• Glycosides
o sugar combined with other organic structure through an ether linkage
o neutral and will not form salts
9
 o generally soluble in alcohol but not in water
o e.g. Digoxin, Ouabin (from foxglove plant)
• Resins: a solid or highly viscous substance of plant (ex. pine, cypress) or synthetic origin that
is typically convertible into polymers
• Gums: secreted by acacia (tragacanth)
• Fixed Oils: stable and do not evaporate when exposed to air
e.g. castor oil, linseed oil, cotton oil
• Volatile oil: evaporate readily (carminative)
e.g. turpentine oil, eucalyptus oil, peppermint oil

EFFECTS OF DRUGS

• Physiological Effect
• Effect that maintains normal body function
o Water is normally taken in as part of food and is essential in the normal function of
the body.
o Insulin, a hormone essential to glucose uptake and giving of sufficient amount to
reduce blood glucose concentration.
• Pharmacological Effect
• Produces exaggerated effects on the animal when administered in excess
o Ex. Too much ingestion of water causes the volume of plasma to increase while
osmolarity (concentration of osmotically active particles) decreases in relation to the
ECF swelling and disruption of cellular function overdose of insulin cause
hypoglycemia (lowered blood glucose concentration)

Paracelsus (full name: Philippus Aureolus Theophrastus Bombastus von Hohenheim)

• Grandfather of Pharmacology
• “All substances are poison. There is none which is not poison.”
• The right dose differentiates a poison and a remedy (medicine)
• A poison can be remedy
o Aspirin at a proper dose relieves pain and fever; overdose may cause stomach ulcers and
bleeding disorders
o Warfarin is a rat poison and caused an internal bleeding due to blockade of the normal blood
clotting process; small dose can prevent intravascular clotting (prevent clogging of blood
vessels with the clot)

4. PHARMACEUTICAL PREPARATIONS (Dosage Forms)

• Preparation of drugs compounded in such a manner as to provide a convenient means of

administering a drug dose to the patient
• Designed for inhalation, oral administration, parenteral injection, or external application

1. Solid Dosage Forms: most common medicinal preparation for oral administration

Advantages:
• Ease of administration
• Stability (provides a long shelf life)
• Uniformity with respect to drug contents

a) Powder
• Simplest solid oral dosage from
• Employed by adding the powder to drinking water (soluble
powder) or feeds

b) Tablet (compressed tablet)

• Most commonly employed oral dosage form
• Consist of an active drug combined with a binder and excipients
• May be scored on both surfaces to facilitate fractionalization for
providing smaller dose
o Tab lets irritating to the stomach or destroyed by gastric juice
maybe coated with phenysalicylate or other substances that is
insoluble on acid but will dissolve in alkaline small intestine
called enteric-coated tablet
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 c) Pills
• Consist of a mixture of drugs and a sticky binder that has been
rolled into a uniform cylinder and cut to form ovoid or
spherical masses, which are then provided with a glazed
sugar coating
• Globular masses consisting of powders drugs mixed with a
gummy excipients and rolled in powder to prevent adhesion
with each other
• Coated with sugar, gelatin or chocolate to disguise their taste on swallowing
o Disadvantage: frequently observed to pass intact through the GIT

d) Capsules
• Hardened containers made up of a mixture of gelatin and
glycerin
• Suitable for drug in powdered forms and certain liquid drugs
o Advantage: drugs with very unpalatable taste, does
not contact the oral mucosa prior to swallowing
o Disadvantage: dose cannot be fractionalized for smaller animals
e) Bolus
• Large compressed tablets, rectangular in shape
• Used for horses and cattle to provide a larger amount of drug required
in the dose without increasing the cross sectionalized size of the
dosage to a dimension that cannot be easily swallowed

f) Suppositories
• Intended for rectal, uretheral or vaginal use
• Made of medicinal substances incorporated in a base
glycinerated gelatin, which melt at body temperature
o rectal suppositories – usually cone shape
o vaginal suppositories – globular
o urethral suppositories – pencil shaped

g) Lozenges
• Oblong, circular, or rectangular medicated candies composed of
the active substance, sugar and mucilage, which are then air dried
• Intended for mouth and throat medication (pastilles)

2. Liquid Preparation for Oral Administration

a) Mixture
• Aqueous solution or suspension intended for oral administration
• Aromatic water (aqueous solution of a volatile oil such as peppermint or cinnamon)
is frequently employed as vehicles but probably add little to the preparation for animal use
(possibilities of contamination by bacteria or molds and to remedy this, preservative such
as benzoic or chlorobutanol are added to inhibit such growth)
• Aqueous suspension of solid (magmas) which are insoluble or nearly insoluble
substances generally contain a dispersing agent (tragacanth or methylcellulose) to delay
settling has label “ shake well before using to insure uniformity of dosage

b) Syrup
• Dense sugar solution in water containing the medicinal substances
• Solution of medicinal agents, flavoring and coloring agents in an 85% sucrose solution
• Employed as cough remedies

c) Elixir
• Hydro-alcoholic solution of medicinal substances that have been sweetened and flavored
characterized by pleasant taste and stability and capable of masking bitter taste
• Usually contained 25% alcohol (better keeping qualities than mixture)

d) Emulsion
• Suspension of minute globules of oily drugs permanently dispersed in aqueous medium,
usually containing flavoring
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 e) Gargles
• Watery solutions of a medicament which may or may not be flavored
• Used for rinsing the mouth and throat

f) Extraction
• Infusion (warm or cold water is used)
• Decoction (boiling of water is used)

3. Parenteral Administration Form

• Commonest: stable aqueous solution
• Less frequent: active component dissolved in an inert vegetable oil → delayed absorption
• Subcutaneous implants of solid dosage forms: prolonged released preparation

Precautions in using prolonged controlled released preparation

a. Avoid accidental IV administration: may cause microembolism
b. Persistent drug residues in food animals have ethical and legal consequences
c. The stability of solutions intended for parenteral administration usually is quite delicate and
dependent upon:
a) pH
b) Temperature
c) Stabilizer
d) Solubilizer
e) Preservative
d. Single or multiple injections should be avoided unless there is proof that the formulations are
physically and chemically compatible

Types of dosage from:

a) Injection
• Sterile solutions or suspension in an aqueous (sometime an oil) vehicles
Characteristics:
1. Heat sterilized (most) or if unstable to heat, filtered through millipore filters
2. Some drugs are unstable in solution and are packaged aseptically in vial (reconstituted
with sterile water immediately before use)
3. Must be free of particulate foreign substances and pyrogen
4. Should be nearly isotonic
5. Supplied in ampules, multi-dose vials or large volume capped bottles to which an
intravenous infusion set may be attached.
6. Should not be stored in syringes for any length of time prior to use, as some drugs will
adsorb to either glass (insulin) or plastic (diazepam) walls of the syringe and inadequate
doses will be delivered
o Syringes and needles must be clean and sterile and needles must be sharp
o Disposable syringes and needles should be promptly destroyed after use

b) Repository/suppositories
• Designed to prolonged effective drug concentration in the body by providing sustained
release from the dosage form thus delaying absorption

c) Implants
• Very hard, sterile pellets inserted under the skin where they dissolve very slowly

4. External Dosage Form

• Drugs are applied locally/skin surface ( eyes, mouth, throat, urethra, vagina, uterus, rectum,
bladder) to mucous membrane to achieve anti-infective, anti-inflammatory, decongestant,
astringent, or anesthetic effect
• Absorption into systemic circulation also occur
• Dermal application: ointment, cream, paste, dusting powder, lotions, sprays, liniment systemic
effect may occur due either to licking of the applied medication or per cutaneous drug absorption
(especially when the skin is damaged or inflamed – burn, ulcers, wounds, dermatitis)
• Drug forms most frequently administered by the mucosal route include: solutions, suspension,
and suppositories
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 • Less commonly used forms: creams, ointment, tablet, powder, sprayers, and tampons
intrammamary infusion of ointments containing anti-bacterial and ant-inflammatory agents is
frequently employed for the treatment of bovine mastitis.

a) Liniments/Braces
• Liquid or semi-solid preparation applied to the skin with inunction (i.e. the rubbing of ointment
or oil into the skin)
• Contains counter-irritant to relieve muscles or tendon pains

b) Lotions
• Solutions of suspensions of soothing substances to be applied to the without friction

c) Ointment
• Semi-solid greasy preparation in which the drug is dissolved or dispersed in a suitable base
(petrolatum, lanolin, or polyethylene glycol)
• Left in consistency and intended for inunction

d) Cream
• Incorporate a drug in a water oil emulsion
• Water will evaporate following application, leaving the drug and a thin film of oil in the skin

e) Dusting Powder
• Mixture of drug in powder form for application to external surfaces
o Adsorbent (e.g. corn starch)
o Lubricant (Talcom)

f) Topical insecticides and wounds dressing

• Frequently prepared as aerosol

5. Other forms of Drugs

a) Enema
• Fluid containing medicaments intended for flushing the lower portion of the colon

b) Spirit/Essences
• Alcoholic solution of volatile substances, especially oils, containing 90% volume of alcohol

c) Tinctures
• Alcoholic or mildly alcoholic solution of the extract of the crude drug

ROUTES OF ADMINISTRATION
• Entry points of drugs into the body
• Administration of Drug
o Produces reactions on gross mammalian physiology, attempt shall be made to clearly
visualize:
a) Primary action of drugs on specific cell –receptors
b) Unit structures of tissues their membrane and specific enzymes system

o Depends upon the intention of the veterinarian, which may be either a strictly local action
or a more widely distributed systemic effect or a combined local and systemic
manifestation

• Local Application
o Protection of the surface upon which drug is applied or production of some reflex action
• Local antiseptic
• Local anesthetic

• Systemic Application
o Either parenterally or enterally
o Absorbed into the blood and transported to the different organs or tissues and where they
exert their main actions, thus they manifest their systemic effects

FACTORS TO CONSIDER IN CHOOSING ROUTE ADMINISTRATION:

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 a) Qualitative type of response desired
• Magnesium sulfate solution given IV will cause muscle relaxation or paralysis but given per os
may produce purgation
• Gentamycin injected: control systemic infection; given per os it modifies the bacterial flora of
the intestinal tract
b) Chemical Properties of drugs
• Procaine penicillin: insoluble in water and available as suspension; injected IM not IV
• Acid labile drugs: destroyed by gastric enzyme when given orally (e.g. insulin, heparin)

c) Pathologic state of the animal

• Drugs are poorly absorbed from the muscle, or SQ tissue of an animal in circulatory shock

d) Therapeutic indication

e) Species of animal (temperament)

• Wild animals that are vicious

f) Ease of handling and controlling the animal

g) Convenient both to the owner and Veterinary Surgeon

A. ENTERAL ROUTE
• Through the digestive tract

1) Oral Route (by mouth, per os, per orem, P.O.)

• most ancient way to administer drugs
• absorption occurs mostly in duodenum but in some cases may also
occur in the mouth, stomach or colon
• not useful in patient with clinical signs of vomiting and gastric irritation or
animals that are vicious and uncooperative or in unconscious animals
• In adult Ruminant: not particularly beneficial, except when local effect
in the rumeno-reticular compartment is desired

Reasons:
a) Drugs diluted in the rumen and reticulum maybe rendered
ineffective
b) Metabolically attacked and inactivated by ruminal
microorganism
c) Antibiotic (especially) may kill or inhibit ruminal
microorganism which may lead to digestive disturbance
Advantages:
a) generally safe
b) most economical
c) sterility not a requirement
d) danger of acute drug reaction is not great
e) most practical in medicating a large herd or flock of animal

Disadvantages:
a) Slower onset of action → rate of absorption from the gut is generally slow
b) Drugs may be inactivated in the digestive tract of monogastric animal (exposed to low pH)
e.g. Penicillin G is inactivated by Gastric acid and food in the stomach delays in
absorption
c) Required large dose
d) Irritant drugs may cause vomition
e) Transit time may be modified by GIT disturbances
f) Unpredictability and inconsistency of absorption
g) Procedure may be difficult in uncooperative and vicious animal
h) Poor technique or presence of dysphagia may lead to intra-tracheal delivery and
subsequent bronchopneumonia

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 o generally, the rate and extent of absorption of a given drug will be greater in carnivorous
animal than in herbivores due to differences in physiology and amount of indigestible bulk
contained in the GIT

2) Intraruminal injection: injection of drug directly into the rumen

3) Rectal route: seldom used in animals except in giving enema to constipated gut

B. THE PARENTAL ROUTE

• absorption is usually more rapid and predictable than the oral route
• drug is administered in order to bring a systemic or local effect
• introduction of drugs at sites of the body between the enteric canal and the integuments
Characteristics:
a) Preparation of drugs must be sterile and free of pyrogen
b) Site of injection must be clean and disinfected with alcohol or iodine to reduce chances of
introducing infectious agents into the body
c) Drugs preparation designed for injection are frequently adjusted to the body tonicity and
needles and syringes should be properly sterilized

Rates of absorption of different drugs differs widely:

• Slowest in SQ injection
• More rapid in IM
• Onset of effect is usually immediate in I.V.

Local Effect: not proceeded by drug absorption, administration enterally or parenterally drug is applied on
the site where its effect is wanted. These sites includes:
o Intradermal
o Intra-articular
o Oral or Rectal (for drug bot absorbed from GIT)
o Intrathecally (spinal Cord membrane)
o Intra-mammary
o Intra-uterine
o Topical (intra lesional → applied into the lesion)

Systemic Effect: requires the absorption of drug and distribution at its site of action

1) Intravenous (IV) injection

Used for: Lateral saphenous injection in a dog
• Emergency treatment and where a rapid effect or
response is needed
• Drugs too irritant/irritating to be deposited in the
tissue or for any other route
• For very precise dosage control (such as
administration of anesthesia → given slowly or to
effect
• Long term administration of drug with transient action by an IV drip

Method requires:
• Thorough asepsis
• The needle is introduced in the veins, the drug is released slowly except in certain cases
• To reduce the chances of causing drug reaction, allow at least one circulation time (about 1 to
2 minute) to complete an intravenous injection
• Some instances maybe longer than that in pentobarbital (sedative-anesthetic) to effect
• Drug preparation must be pure, sterile and exist as a true solution
• Remove the bubbles inside the syringe
• The usual barrier to absorption is by-passed, the actual rate of absorption is limited by the
rate of injection which is under the control of the injector

Disadvantages:
• Short duration of action
• Adverse effects usually are more severe
• There is no redress once injection had been made
• Difficulty in injecting the needle inside the veins in young animals
15
 • IV injection of particulate suspension may result in death from pulmonary embolism

2) Intramuscular (IM) injection IM site in horse

• done by inserting the needle vertically through the layers of the skin into
the muscle, where the drug is released
• convenient in animals that may be difficult to restrain
• drug suspension may be injected
o care should be exercise so that the needle does not enter a blood
vessel. This may be checked by pulling the plunger of the syringe.
The absence of blood entering the syringe on pulling the piston
indicates that the needle is outside a blood vessel. This procedure
should be strictly followed specially when drugs dissolved in oil are to be given.
• used for relatively irritant drug for aqueous suspension or solution
• should be made deep in the belly of a large muscle to reduce the chance of IM injection into a fascial
plane where absorption might be erratic duration of drug action is longer than for IV injection but must
often is little shorter than SQ Administration

Disadvantages:
a) Possibility of improper deposition of the drug preparation in nerves, blood vessels, fat or
between muscle bundles in connective tissue sheath
b) Moderately irritant drug may cause necrosis

3) Subcutaneous (SC)
• needle is inserted through the layers of the skin sand
the drug is deposited in the areolar tissue
• response is more prompt than that of the oral route
• usual dose is generally half that required for oral
administration
• generally employed for administration of relatively
large volume of non-irritating solution or medication
that may produce an moderate degree of muscular
soreness
• absorption is almost as fast as in the intravenous
SC site in dogs
route because the drug goes to the circulation easily
• chosen when a slow and continuous absorption of a
drug is required (provided that the formulation approaches body pH and tonicity is not irritant or
vasoconstricting; oily vehicles should be avoided

e.g. Pelleted medication for long term therapy (implanted SQ)


Deoxycorticosterone acetate (treatment of hypoadrenocortisone)

• rate of drug absorption from SQ site can be manipulated to some degree of application of:
a) Heat: increase rate of absorption
b) Cold: delayed the rate of absorption
c) Hyalurinadase: increase rate of absorption
d) Massaging the site of Injection: increase rate of absorption (enhances the dispersion)

Disadvantages of SC:
• Injection of irritant or unstable medicinal substances may lead to inflammation, abscess formation and
necrosis
• Danger of infection could be prevented by proper asepsis of the area and of the instrument used.
• Rate of absorption is unpredictable and depends upon:
o Blood flow (most important
o Presence of vasoconstrictor or vasodilator which substantially alter the rate of evaporation

4) Intrapleural (IP)
• A small aseptic opening is made on the abdominal wall through which a needle is passed to the
peritoneal cavity where the drug is deposited
o Peritoneum provides a larger surface area for absorption of drugs
• Important in large animal for the administration of large volume due to great absorbing surface and
rapid absorption rate
• Usually used in experimental animals
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Disadvantages of IP
• Must be careful to place the needle through an area of the abdominal wall within which there not be a
likelihood of penetrating a visceral organ
• Extremely irritating compounds may induce chemical peritonitis
• Seldom used clinically due to danger of infection of the peritoneum and adhesion of the same with
neighboring structures

5) Intrathecal (Subarachnoid space, Intraspinal injection))

• Done by inserting the needle through the intrapinous process into the spinal canal with the purpose of
introducing the drug to produce local meningeal and cerebrospinal action (spinal anesthesia)
specifically in the lumbar area or into the cisterna magna
• Strict aseptic technique must be followed and the drug must be a non-irritating solution

6) Sub conjunctival or Intraocular

7) Intraperitoneal
8) Intrasynovial
9) Intranasal
10. Inhalation
• use of volatile substances in therapy
• gases and hydrocarbon anesthetic
• oxygen is most commonly used in daily practice
11) Intra-tracheal
12) Intra-arterial
13) Intradermal: testing for hypersensitivity, for vaccination
14) Epidural Route: 1st and 2nd coccygeal vertebrae; anterior epidural → lumbosacral space
15) Vaginal Route
16) Intra Cardiac Route
17) Intra-articular route: joint capsule
18) Rectal Route
• Rectum is also highly vascular and drug given per rectum oftentimes produce a more prompt and
intense action than when administered through the mouth.
• Best given in solution in the form of retention enemas.

FREQUENCY OF ADMINISTRATION (DEPENDS ON THE FOLLOWING FACTORS):

1) Characteristic of the disease
• If the disease is very acute and severe, then, with regard to toxicity consideration, frequent
massive doses are indicated to save the animal’s life
• Where subacute conditions are involved, less urgent and heroic measures are necessary, and
providing adequate tissue levels are achieved, high and frequent dosage is not necessary
2) Character of the Drug
• Some drugs are absorbed and excreted more rapidly than others and the dosage of these drugs
must be sufficiently frequent to maintain adequate tissue concentration
• Toxicity of the drug also has a bearing on dosage
3) Animal Physiology
• Ruminant due to mass depot of rumen need only twice daily oral dosage but parenteral dosage
follows normal practice
4) Ability of the Owner to administer the drug at the required interval

Duration of Treatment
• It depends entirely on the nature of the disease and the number of doses will vary accordingly, but a
sufficient number to allow for wastage and flexibility of revisiting should be prescribed.

5. PHARMACOTHERAPEUTICS

Basic Concepts in Veterinary Pharmacotherapeutic

Once a diagnosis has been established, there are 4 main options:
1) Do nothing
2) Medical treatment
3) Surgical Intervention
4) Euthanasia

An additional important responsibility is to make provision for the care, comfort, feeding and alleviation
17
of pain or suffering of the affected animal. When medical treatment is deemed necessary, safe and effective,
pharmacological agents that possess the appropriate actions should be selected.

Also to be considered are:

1) dose rates
2) frequencies of administration of the chosen drugs
3) The optimal routes for delivery
4) The pharmaceutical forms to be used
5) Any public or environmental implication and regulatory constraints
6) Proper concern also must be given for the handling, storage, stability, incompatibilities,
bioavailability, and potential drug or nutrient interactions with pharmaceutical [products; failure to
do so may result in therapeutic failures.

Following administration of selected agent, a complex series of events occur, which govern in large
measure the disposition of the drugs and the ultimate clinical success (or failure) of the regimen selected.
An understanding of the fundamental pharmacological principles involved, together with an
appreciation of the major attributes of each class of drug, form the basis of rational pharmacotherapeutic.

Considerations in Drug Use

1. What is your therapeutic goal? What specific pathologic process do you wish to alter by using a drug
from this class and this drug in particular? Is it absolutely necessary that you use this or any drug?
2. By what routes can the drug be given for the indication in question and which are you going to use?
On What basis did you make this decision?
3. What dosage forms are going to use?
4. What dose in unit/kg or mg/Kg is generally recommended and how much are you using in this
particular animal? How did you arrive at t his dosage? Are these items considered “precautions” that
should modify the dose in this animal?
5. What is the dosage interval? Is this going to be frequent enough to prevent the drug from dropping
below effective concentration? Will it be too frequent and precipitate the accumulation and toxicity?
6. What is the probable duration of therapy?
7. For food animals? Is the drug approved for use in the food producing species? What is the withdrawal
time?
8. How much does the drug cost per treatment and per expected duration of therapy? Does the cost of
treatment exceed the value of the animal or the desire of the owner to pay? Is the cost appropriate to
the seriousness of the disease?
9. What special precautions must be observed to enhance its effectiveness or safety? Will the drug
interact with other drugs in the regimen?
10. What are the contraindications to the use of the drugs?
11. What adverse reactions might one reasonably expect to see? How would you monitor the animal to
detect potentially serious reactions before they are permanent or endanger the animal life?
12. What course of action will you take if you elicit drug reaction? Do you have the requisite drugs and/or
equipment on hand?
13. What plans do you have for evaluating the results of your therapy? By what parameter (s) will you
judge whether the animal is responding to treatment? Where can you reasonably expect to see the
first response? How will you judge whether you have cured the animal? What follow-up procedures
should be instituted?
Drug Presentation:
a. First: selection of an appropriate drug for therapy begins with establishment of an accurate
diagnosis
b. Once satisfied that the disease or dysfunction present in the patient has been determined a
decision is reached on the available options for subsequent therapy based on:
• understanding of disease
• pharmacology of possible choice
c. Decide the route by which to administer the medicament, dosage form use, and dose interval
d. Client must be provided with instruction how to administer the drug and supply of medication
(either dispensed of prescribed)

18