Pharmacology

Ø Pharmakon – “drug”
Ø Logia- “study of” / refers to the study of biological effects of chemicals.

Drugs
Ø Chemicals introduced into the body to elicit change. Change in func?on.

Pharmacotherapeu2cs/Clinical Pharmacology
Ø Use of drugs to treat, prevent, and diagnose disease.

Two key concerns:

1. Drug’s effects to the body

2. Body’s response to the drug.

Nurse du2es

1. Administra?on
2. Assessment of effects
3. Intervene regimen.
4. Pa?ent teaching
5. Monitor pa?ent care plan.

Sources of drugs

Ø Natural (Plants, Animals, Inorganic Compounds)

• Plants – main component of alterna?ve therapy movement (alterna?ve
medicine)
Plants (Analgesics, Morphine, Codeine – poppy plant) (Digitalis: heart drug – purple
fox glove/digitalis Proporea) (An?-Malarial drug: Quinine- bark of cinchona)
• Animals – replacement for human chemicals they failed to produce (Insulin, from
pancreas of a cow)
• Inorganic Compounds (Salt, Aluminum: antacid, Fluorine: dental cavi?es, Gold:
osteoporosis, Iron: Iron-deficiency anemia)
Ø Synthe?c

Drug Evalua2on

Ø FDA
• Regula?on and research of drugs, controlled by the FDA.
 1. Pre-clinical trials
• Tes?ng of chemicals with therapeu?c value to lab animals.
• To determine presumed effects (therapeu?c) to living ?ssue and to evaluate
adverse effects (side)

✖ Reasons for discarding some chemicals:

a. Lacks therapeu?c ac?vity.

b. Are too toxic.
c. Highly teratogenic (adverse effect to the fetus)
d. Safety margins are so small.

PHASE I

Ø Uses human volunteers to test the drugs.

Ø Performed by trained clinical inves?gators.
Ø Volunteers are fully informed of the risks and may be paid. (Sign a waiver)
Ø Volunteers are healthy young men. Chemicals may affect woman’s ova.

✖ Reasons for discarding some chemicals:

a. Lacks therapeu?c ac?vity.

b. Are too toxic.
c. Highly teratogenic (adverse effect to the fetus)
d. Safety margins are so small.

PHASE II

Ø Clinical inves?gators try the drug out in pa?ents who have the disease that it is
designed to treat.
Ø Pa?ents are informed of possible effects and risks of the drug if consent to
par?cipate is given.
Ø Can be performed in hospitals, clinics, and doctor’s offices.

✖ Reasons for removal of chemical from further inves2ga2on

Ø Less effec?ve than an?cipated.

Ø Too toxic
Ø Has unacceptable adverse effects.
Ø Low benefit-to-risk ra?o
Ø No more effec?ve than other drugs already in the market.
PHASE III

Ø Use of drug in a vast clinical market.

Ø Prescribers are well-informed of the known reac?ons to the drug and precau?ons are
required- pa?ent should be observed closely.

✖ Reasons for dropping the drug:

Ø Produces unacceptable adverse effects.

Ø Produce unexpected responses especially when used widely.

★ FDA APPROVAL ★

☛ ONLY DRUGS THAT RECEIVED FDA APPROVAL MAY BE MARKETED.

• Brand name: trade name. Refers to an approved drug developed by the

pharmaceu?cal company. Levothroid, Synthroid. Biogesic

• Generic name: original designa?on that a drug is given when the drug company that
developed it applies for the approval process. Levothyroxine sodium. Paracetamol

• Chemical name: Reflects the chemical structure of the drug. L-thyroxine, T4,
Aceaminophen: N-Acetyl P-Aminophenol

☛ Generic and chemical names always appear straight print.

☛ While brand name is always italicized.

Paracetamol
Biogesic

Drug development and approval process may take 5 to 6 years.

Some may be accelerated. Delavirdine (Rescriptor) – For AIDS – s?ll in the produce.

✹ Generics Act of 1988 (Republic Act No. 6675). An Act to Promote, Require and Ensure the
Produc?on of an Adequate Supply, Distribu?on, Use and Acceptance of Drugs and Medicines
Iden?fied by their Generic Names.
PHASE IV

Ø Con?nual evalua?on ader a drug was approved for marke?ng. Dexfenfluramine

(Redux), a diet drug. Rofecoxib (Vioxx)

★ LEGAL REGULATIONS OF DRUGS ★

• Safety during pregnancy: Category A-D & X

• 5 Categories established by the FDA to indicate poten?al for a systema?cally

absorbed drug to cause birth defects.

Ø Controlled drugs – has a poten?al to be abused. Yellow prescrip/on. (An2-

psycho2cs, An2-depressants, Valium, Morphine Sulfate)

Ø Generic drugs – sold by their generic names.

Ø Orphan drugs – are drugs that have been discovered that are not financially viable.

Ø Over-the-counter drugs (OTC) – available without prescrip?on for self-treatment.

(Analgesics, An?-pyre?cs)

★ FACTORS AFFECTING DRUG EFFECTS ★

☛ For drug ac?on to occur, it must undergo 3 phases. But not all undergo pharmaceu?cs.

• Pharmaceu2cs/dissolu2on phase

Ø Drugs need to be in solu?on to be absorbed in the GI tract.

Ø Disintegra?on - Breakdown of tablet into smaller par?cles
Ø Dissolu?on – liquid form – dissolving smaller par?cles into GI before absorp?on.
Ø Excipients – filler and inert substances.

• Pharmacokine2c phase

Ø How the body acts on the drug.

Ø Process of drug movement to achieve drug ac?on.
Ø (ADME)
 1. AbsorpOon – Movement of drug par?cles from the GI tract to the body fluids by:

Ø Passive absorp2on- drugs are absorbed in the body. A greater concentra?on of drug
on one side of a cell membrane means that the drug will move through the
membrane to the area of lower concentra?on (diffusion). Facilitated diffusion
requires assistance. Does not require any cellular energy.

Ø Ac2ve absorp2on/pinocytosis – Uses energy to ac?vely move a molecule across a

cell membrane. Low concentra?on to high concentra?on. Gwen Trinity Balagtas. The
molecules are large and is oden a significant process in drug excre?on in the kidney.
Requires a carrier- enzyme or protein. Cells carry drugs across membrane by
engulfing drug par?cles.

★ FACTORS AFFECTING ABSORPTION

Ø Surface Area
Ø Contact ?me with surface.
Ø When to take
Ø Circula?on
Ø Solubility
Ø Drug form
Ø Drug concentra?on
Ø Bio ability
Ø Route of administra?on
Ø Addi?ves
Ø Enteric coa?ng (pH greater than 7 – alkaline-soluble)
Ø Sustained release drugs
Ø Size of drugs

★ FASTEST TO SLOWEST TO BE ABSORBED ★

1. Liquid
2. Elixir
3. Syrup
4. Suspension
5. Solu?on
6. Powder
7. Capsule
8. Tablet
9. Coated tablet
10. Enteric-coated tablet
 2. DistribuOon

Ø Process by which the drug becomes available to body fluids and body ?ssues.
Transport of drug from the blood to the site of ac?on. Drugs are also distributed to
?ssues where it has no effect so compe??on for drug-binding sites affect the amount
of drug availability for ac?ons in the body.
Factors
Ø Perfusion rate: rate at which blood is delivered to the ?ssue.
Ø Permeability of the membranes
Ø Diffusion: lower to higher concentra?on or vice versa.
Ø Protein binding effect
Ø Tissue localiza?on
Ø Blood-brain barrier
Ø Placenta.

• Blood flow
• The drug’s affinity to the ?ssue
• Protein binding effect
• As drugs are distributed in the plasma, many are bound to varying degree with
protein.
• Highly protein-bound drugs, moderately high, moderately low protein-bound
drugs.
• The por?on of the drug that is bound is inac?ve because it is not available to
receptors, and the por?on that remains unbound is free (ac?ve drug)
• (Only free drugs are ac/ve and can cause a pharmacologic response.)
• High protein drugs are given concurrently, they compete for protein-binding sites
causing more free drugs to release into the circula?on.

★ BLOOD BRAIN BARRIER ★

Ø Semi-permeable membrane (border) in the CNS that protects brain from foreign
substances.
Ø Filtering mechanism of the capillaries that carry blood to the brain and spinal cord
/ssue, blocking passage of certain substances.
Ø Protec?ve system of cellular ac?vity that keeps many things away from the CNS.
Ø Highly lipid-soluble drugs can cross the BBB. (Also, glucose, amino acids, organic
anions and ca/ons.)
Ø Lipid-soluble and lipid-insoluble drugs can cross the placental barrier which can
affect the mother and fetus during pregnancy.
Ø Risk-benefit ra?o should be considered before drugs are given during pregnancy.
Ø Drugs can be secreted into the breastmilk during lacta?on.
 3. Metabolism/BiotransformaOon

Ø process body changes the chemical structure of drug to another form called
metabolite (more water-soluble compound that can be easily secreted.)

Drugs absorbed into the intes?ne.

▾
Drugs absorbed by the portal system.
▾
Liver (most important site of drug metabolism) everything absorbed by the GI tract first goes
to liver to detoxify chemicals.
▾
Drugs bound to plasma protein in the circula?on.
▾
Drugs distributed throughout the body.

☛ First-pass phenomenon- drugs first absorbed through small intes?ne then arrive at the
liver via the portal circula/on.

☛ Portal CirculaOon: Capillaries to vessels to another set of capillaries to vessels then return
to systemic circula?on.

Pharmacogene?cs
• Hereditary influence on drugs responses, how individuals metabolize drug.

Circadian rhythm
• rate of drug absorp?on, hepa?c clearance, half-life, and dura?on of ac?on have
all been shown to differ depending upon the ?me of drug is administered.

Effects of gender and age

• elimina?on of the drug from the body is directly influenced by age.

HALF LIFE
• Refers to the ?me for the amount of drug in the body to decrease to one half of
the peak level it previously achieved.
• Dura?on of the drug’s effect on the body.
✦ E.g., Pa?ent takes 20 mg of a drug with a half-life of 2 hours. 10 mg will remain aFer 2
hours, to 5 mg aFer another 2 hours to 2.5 mg in 2 more hours.
★ FACTORS TO CONSIDER IN DETERMINING THE HALF-LIFE OF A DRUG ★

Ø Absorp?on rate
Ø Distribu?on to the ?ssues
Ø Biotransforma?on
Ø Excre?on

4. ExcreOon

Ø Removal of the drugs from the body.

Ø Skin, saliva, lungs, bile, and feces are routes.
Ø Kidneys play the vital role.
Ø Crea/nine clearance (CLcr) and blood urea nitrogen (BUN) are common tests to
determine renal func?ons.
Ø High crea/nine and BUN indicate a large amount of toxins in the body due to poor
filtra/on and excre/on.
Ø Glomerular filtra/on rate (GFR) is the best test, but it is expensive.

• Pharmacodynamics

Ø Interac?ons between the chemical components of living systems and the foreign
chemicals, including drugs that enter those systems.
Ø What a drug does to a body
Ø Mechanism of drug ac?on to living ?ssue.

★ Drugs 4 ways to work:

Ø To replace/act as subs?tutes for missing chemicals.

Ø S?mulate certain cellular ac?vi?es.
Ø Slow cellular ac?vi?es.
Ø Interfere with the func?on of foreign cells such as invading microorganisms or
neoplasms. (Chemotherapeu/c agents.)

★ Effects of drugs: Therapeu?c

Ø Cura?ve – cures a disease of condi?on (PT has TB, needs an?-tb medica?on)
Ø Suppor?ve – support a body func?on un?l the treatment or the body response can
take over (PT has low hemoglobin, give erythropoie?n.)
Ø Subs?tu?ve – Replaces body fluids. (IV medica?on for people who have dehydra?on)
Ø Chemotherapeu?c – destroys malignant cells.
Ø Restora?ve – returns the body to health.

RECEPTOR SITES

Ø Refers to specific areas where drugs are thought to act on cell membranes.

• Lock (cell membrane) and key (enzyme) theory

• Agonist interac2on with receptor site (some drugs interact directly with receptor
sites that cause the same ac/vity that natural chemicals would cause at that site)

• CompeOOve antagonism – some drugs react with receptor sites to block normal
s?mula?on, producing no effect.

• NoncompeOOve antagonism – other drugs react with specific receptor sites on a

cell, preven?ng the reac?on of another chemical with a different receptor site on
the cell.

• Selec2ve Toxicity

• The ability of a drug to akack only those systems found in foreign cells.
(E.g., Penicillin - affects enzyme unique to that bacterium.)

★ CONTRIBUTING FACTORS TO 3 PHASES ★

Ø Weight
Ø Age
Ø Gender
Ø Physiologic
Ø Pathological
Ø Gene?c
Ø Immunological
Ø Psychological
Ø Environmental
Ø Drug-drug interac?ons (certain medica?ons may increase the effect of other
medica?on that why they’re not to be taken together.)
Ø Drug-food interac?ons
 TOXIC EFFECT OF DRUGS & THE NURSING PROCESS

• Drug allergy

• Occurs when the body forms an?bodies to a par?cular drug, causing an immune
response when the person is re-exposed to the drug. (Such as allergy to
ibuprofen.)

• Rashes, Hives

Procainamide (Pronestyl)

• Treats cardiac arrhythmias can cause a skin rash.

• Instruct the pa?ent to avoid scratching or rubbing the lesions and avoid harsh
soaps and lo?ons.

DRUG INDUCED TISSUE AND ORGAN DAMAGE

• STOMATITIS (Inflamma?on of the mucous membrane)

• Fluoracil (Adrucil) is an an?neoplas?c agent which causes mouth sores or

stoma??s. (Provide frequent mouth care, give frequent small meals)

• BLOOD DYSCRASIA

• Bone marrow suppression caused by drugs such as an/neoplas/cs.

• Fever, chills, sore throat, weakness, back pain, or pancytopenia (Below normal
value of RBC, WBC, and platelet.) (Monitor blood counts and provide protec/ve
measures against bleeding and infec/on.)

TOXICITY

• LIVER INJURY

• Fever, malaise, nausea, vomi?ng, jaundice, change in color of urine/stool,

elevated liver enzymes (AST & ALT) (Discon/nue the drug if these happens.)

✦ AST – Asperate Aminotransferase

✦ ALT – Alanine Transaminase
 • RENAL INJURY

• Elevated BUN and crea?nine, decreased hematocrit, electrolyte

imbalances. (Discon?nue drug as needed.)

ALTERATIONS IN GLUCOSE METABOLISM

• HYPOGLYCEMIA

• Drugs such as Glipizide (Glucotrol) and glyburide (DiaBeta) are an?diabe?c

agents that can lower blood glucose.
• Fa?gue, drowsiness, hunger, shaking and trembling. (Restore glucose
immediately.)

• HYPERGLYCEMIA

• Ephedrine is a drug used as bronchodilator, can break down stored glycogen

and can elevate blood glucose.
• Fa?gue, increased urina?on, increased thirst, deep respira?ons, restlessness.
(Administer insulin to decrease blood glucose.)

ELECTROLYTE IMBALANCES

• HYPOKALEMIA

• Loop diure?cs such as Furosemide (Lasix) can increase potassium excre?on.

• If potassium is below 3.5 mEq/L, replace serum potassium. (Check order
when administering potassium.)

• HYPERKALEMIA

• Potassium-sparing diure?cs such as Spironolactone can increase potassium

serum levels.
• Ins?tute measures to decrease the serum potassium, monitor cardiac effects.
SENSORY EFFECTS

• OCULAR TOXICITY

• Chloroquine is a drug used to treat some rheumatoid disease and can cause
re?nal damage and blindness.
• Monitor pa?ent’s vision when receiving oculotoxic drugs: provide suppor/ve
measures when there is blurring of vision.

• AUDITORY DAMAGE (OTOTOXICITY)

• Aspirin is one of the most common ototoxic drugs affec?ng the 8th cranial
nerve.
• Monitor pa?ent’s perceptual losses or changes, provide suppor?ve measure
to cope with drug effects.

NEUROLOGIC EFFECTS

• Beta-blockers, treats hypertension, can cause feelings of anxiety, insomnia, and

nightmares. (Provide safety measures to prevent injury. Tell pa/ent to avoid driving or
opera/ng dangerous machinery.)

ATROPINE-LIKE (ANTICHOLINERGIC EFFECTS)

• Atropine sulfate, an?depressants, and an?psycho?cs have an?cholinergic effects.

(Provide hard candy for dry mouth, arrange bowel program for cons/pa/on, safety
measures is vision changes occur, avoid sunlight etc.)

PSEUDOPARKINSONISM

• Many an?psycho?cs and neurolep?c drugs can cause this effect. (Discon/nue the
drugs or give an/parkinsonian drugs (CAPABLES) as prescribed.

NEUROLEPTIC MALIGNANT SYNDROME

• General anesthe2cs and other drugs that have direct CNS effects can cause NMS.
• Extrapyramidal symptoms, (involuntary muscle contrac?ons, tremors etc.)
hyperthermia is present. (Discon/nue the drug.)
THE NURSING PROCESS IN DRUG THERAPY AND PATIENT SAFETY

• Nursing process is a decision-making problem-solving process used by nurses to

provide efficient and effec?ve care.
• Ensures that the pa?ent receives the best, safest, most efficient, scien?fically based,
holis?c care.

✧ DOSAGE CALCULATIONS ✧

RIGHTS OF DRUG ADMINISTRATION

1. Right client
• 2 PATIENT IDENTIFIERS: (wrist band, and a second piece of
iden/fica/on such as picture on the chart. Must be done before
administra/on of medica/on.)
2. Right drug
• CORRECT AND ACCURATE: client receives drug prescribed by a
physician (MD), den?st (DDS), podiatrist (DPM) or an advanced prac?ce
nurse with the license to write prescrip?ons. (APRN)
• INNOVATION: use of computerized systems to record medica?ons help
decrease medica?on errors. Phone or verbal orders must be cosigned
by the prescribing physician within 24 hours.
3. Right dose
• ACCURATE AND ADVOCATE: the right dose is prescribed for a par?cular
client. The nurse is responsible for ques/oning any dose that looks too
high or too low. Always consult a peer or pharmacist if dosage appears
incorrect.
• Beware of pediatric doses that are based on body weight as weight can
change daily so regular assessment of dosages is crucial.

★NURSING IMPLICATIONS★

• Calculate the drug dose correctly. Some medica?ons need two nurses to sign off a new
order such as heparin and insulin.
• Check the PDR. Drug package inserts, or other drug references for recommended
range of specific drug doses.
 4. Right 2me
• Time at which the prescribed dose should be administered. (E.g., every
6 hours)

★NURSING IMPLICATIONS★

• Administer drugs at specified ?mes. Drugs may be given 0.5 hour before or ader
the ?me prescribed if the administra?on interval is > 2 hours.
• Administer drugs that are affected by foods before meals. (E.g., tetracycline.)
• Administer drugs that can irritate the stomach (gastric mucosa) with food such as
aspirin or potassium.
• The drug administra?on schedule can some?mes be flexible to accommodate the
client’s ac?vi?es for the day or preferences.
• Responsibility of the nurse to be aware of tests or procedures that are taking place
that may affect the medica?on administra?on (e.g., fas?ng blood tests, endoscopy)
• Check the expira?on date on medica?ons and return to pharmacy if expired.
• An?bio?cs need to be given evenly over 24 hours as opposed to T.I.D

5. Right route

• IM, IV, ID, PO, SQ, SUBLINGUAL, TRANSDERMAL, INHALATION

★NURSING IMPLICATIONS ★

• Assess client’s ability to swallow before administering PO.

• Do not crush or mix medica?ons into other substances before consulta?on with
the pharmacy. Do not mix meds into sweetened juices for kids to add to formula
for babies. Follow all med administra?on guidelines for that specific drug.
• Use asep?c technique when administering drugs. Use sterile technique when
administering parenteral meds.
• Administer drugs to appropriate sites.
• Stay with client un?l PO meds have been swallowed.
• If it’s necessary to combine a medica?on with another substance, explain this to
the client.

5 ADDITIONAL RIGHTS

1. Right assessment
2. Right documenta?on
3. Client’s right to educa?on
4. Right evalua?on
5. Client’s right to refuse.

COMPONENTS OF A DRUG ORDER

Ø Date and ?me the order is wriken.

Ø Drug name (generic is preferred)
Ø Drug dosage
Ø Route of administra?on
Ø Frequency and dura?on of administra?on
Ø Physician or other healthcare provider’s signature or name.

(Any special instruc/ons for withholding or adjus/ng dosage based on nursing assessment,
drug effec/veness, or laboratory results.)

(If any components are missing, the en/re order is incomplete, and the medica/on should
not be given.)

To avoid error, nurse must check the bokle against the order for the medica?on 3 different
?mes.

1. At the Ome of contact with the container

2. Before pouring the drug
3. A[er pouring the drug

Drugs given for the first dose, one-?me, or PRN medica?on should always be checked
against the original order.

Beware of medicaOons that sound alike and read labels carefully. (E.g.,; Percocet which
contains oxycodone and acetaminophen, while Percodan contains oxycodone and aspirin.)

Percodan should not be given to someone who has an adverse reac?on to aspirin.

★ NURSING IMPLICATIONS:

• Check that medica?on order is complete and legible.

• Know why the client is receiving the medica?on.
• Check the drug label three ?mes before administra?on.
• Know the start date that the drug was ordered and the ending date.

★ FOUR CATEGORIES OF DRUG ORDERS:

1. STAT - immediately
2. STANDING ORDERS – do when you receive a patient.
3. ONE TIME
 4. PRN – as necessary

★ MEDICATION SAFETY TIPS ★

1. AVOID DISTRACTIONS

• Hospital is full of interrup?ons and distrac?ons. 45-50% of medica?on errors are due
to these factors.
• Focus. Distrac?on during prepara?on and administra?on can cause errors.
• Distrac?ons: from ringing telephones, call bells, to short-tempered pa?ents can
disrupt your focus.

2. KNOW YOUR Rs

• The rights of Drug Administra?on aren’t that hard to memorize. Put them into prac?ce,
however, can be a different story if it’s the first ?me you’re administering a medica?on.
• The anxiety, fear, and tension can easily put you at risk of commirng an error. Because
of this, certain hospitals implement policies to help new nurses hone their skills
without risking the welfare of their pa?ents.
• Know the 10 rights of drug administra?on.

3. ALWAYS ASK AND COUNTERCHECK

• Medica?on errors involve miscommunica?on and false assump?ons.

• There’s nothing wrong verifying the doctor’s handwri?ng. Gerng shouted by an
annoyed doctor is beker than a dead pa?ent.
• It is standard prac?ce for another nurse to recompute and double check.
Miscalcula?on can debilitate your pa?ent.

4. STAY UPDATED

• Medica?on reconcilia?on – involves crea?on of complete list of medica?ons your

pa?ent is receiving and constantly upda?ng the list as transi?on of care happens or if
there are any changes in his medica?on chart.
• MAR (Medica/on Administra/on Record)

5. LABEL PROPERLY

• It is universal prac?ce to keep every syringe, vial, or container properly labeled to avoid
medica?on error. Label ports and medica?ons- label every syringe or container that
has medica?on in it. Even bowls, catheters, and receptacles have labels on them just
to make sure.
6. REPORT

• Report the incident in case an error occurs. No?fy all members of the healthcare team
in charge of the pa?ent’s care as well as the hospital safety commikee.
• You may also need to inform the rela?ves of the pa?ent as to what went wrong and
how the error was managed.

7. CHECK ON ANTIDOTES

• Wrong drug and route can pose fatal risks to your pa?ents. Some incidents can
lead to a life lost, if not handles properly.
• Aside from emergency drugs, have the basic an?dotes on stock. Keeping them
within easy reach will enable you to respond quicker to emergent cases.

✦
 METRIC SYSTEM

• A decimal system based on the power of ten.

• Basic unit of measurement are:

Gram for weight

Liter for volume
Meter for linear measurements or length

APOTHECARY SYSTEM

★ Solids: grain (gr)

60 gr = 1 dram (dr)
8 dr = 1 ounce (oz)

★ Liquids: minim (min)

60 minim = 1 fluidram (f dr)

 HOUSEHOLD SYSTEM

★ Solids: pound (lb)

1 lb = 16 ounces (oz)

★ Liquids: pint (pt)

2 pt = 1 quart (qt)
4 qt = 1 gallon (gal)
16 oz = 1 pt = 2 cups ©
32 tablespoons (tbsp) = 1 pt
3 teaspoons (tsp) = 1 tbsp
60 drops (gh) = 1 tsp

METHODS FOR CALCULATIONS/DRUG CALCULATIONS

★ Tablet Dosage CalculaOons

- Used to calculate the number of tablets to be administered when given

the required dose.

• Required dose.
------------------ = Number of tablets to be given.
Stock dose

Units for required dose and stock dose must be the same.

§ Example 1:

A client is ordered 150 mg of aspirin. 300 mg aspirin tablets are available. How many
tablets will you give?

150 mg
------------------ = ½ tablet.
300 mg
 § Example 2

How many tablets containing 62.5 mcg will be required to give a dose of 0.125 mg?

Step 1: convert to same unit (0.125 mg to mcg)

Step 2: calculate.

125 mcg
------------------ = 2 tablets
62.5 mcg

§ Example 3

OR convert 62.5 mcg to mg. The decimal place is moved 3 places to the led:
62.5 mcg (6.25/1000 mcg) = 125 mcg

0.125 mg
------------------ = 2 tablets
0.0625 mg

★ Fluid dosage calculaOons

- Used to calculate the amount of medica?on in solu?on for oral,

intramuscular, intravenous, or subcutaneous injec?on to be
administered when given a dosage, stock dose, and volume.

Required dose. Stock volume

---------------------- x ---------------------- = volume to be given
Stock dose. 1

• Example 1

A client is ordered 15 mg of Steme?l. You have 2 ml of the solu?on on hand which

contains 25 mg Steme?l. How much volume of the solu?on will you give?

15 mg 2 ml
---------------------- x ---------------------- = 1.2 ml
25 mg. 1
• Example 2

A dose of 75 mg pethidine has been ordered. It is available in ampules containing 100

mg in 2 ml. How much are you going to administer?

75 mg 2 ml 150
---------------------- x ---------------------- = ------------ = 1.5 ml
100 mg. 1 100

★ Intravenous Fluid ComputaOon

- Must be given at a specific rate, neither too fast nor too slow. The
specific rate may be measured as ml/hr, L/hr or drops/min. To
control or adjust the flow rate, only drops per minute are used.
The burette contains a needle or plastic dropper which gives the
number of drops per ml (the drop factor.) A number of different
drop factors are available (determined by the length and diameter
of the needle.)

★ Common drop factors:

10 drops/ml (blood set)

15 drops/ml (regular set) (macro set)
60 drops/ml (micro drop) (micro set)

The number of drops, time in minutes.

★ Formula for working out flow rates is:

Volume (ml) x drop factor (drops/ml)

------------------------------------------------
Time (min)
• Example 1

1500 ml of IV Saline is ordered over 12 hours. Using a drop factor of 15 drops/ml,

how many drops per minute needs to be delivered?

1500 (ml) x 15 (drops/ml) 22,500 ml

------------------------------------------------ = ------------------- = 31 gks/min
12 x 60 (gives us total min) 720 min

★ Formulas for pediatric dosages

• Fred’s rule

Child’s dose (age < 1 year):

= infant’s age in months x adult dose

150 months

• Young’s rule

Child’s dose (aged 1-12 years):

= child’s age in years x average adult dose

Child’s age in years + 12

• Clark’s rule

Child’s dose:

= weight of child in pounds x average adult dose

150 pounds