Unit1

1Q Define Drug and Classify different routes of drug administration.

Describe different types of parenteral routes?

1A Drug and Routes of Drug Administration

Definition of Drug

A drug is any chemical substance that, when administered to a living

organism, modifies physiological functions to diagnose, treat, cure, or
prevent disease. Drugs can be derived from natural sources (plants, animals,
minerals) or synthesized in laboratories.

Classification of Routes of Drug Administration

Routes of drug administration refer to the various ways in which drugs can
be delivered into the body for therapeutic effects. These are broadly
classified into:

1. Enteral Routes (Via the Digestive Tract)

These involve drug administration through the gastrointestinal (GI) tract.

 Oral (PO) – Swallowed and absorbed in the stomach/intestines (e.g.,

tablets, capsules).

 Sublingual (SL) – Placed under the tongue for rapid absorption (e.g.,
nitroglycerin).

 Buccal – Placed between the cheek and gums (e.g., fentanyl buccal
tablets).

 Rectal (PR) – Administered via the rectum (e.g., suppositories for

nausea).

2. Parenteral Routes (Bypassing the Digestive Tract – Injectables)

These involve drug administration via injections for faster absorption and
direct systemic effects. (Discussed in detail below)

3. Topical Routes (Local Effect on Skin or Mucous Membranes)

 Dermal – Applied to the skin (e.g., creams, ointments, gels).

 Ophthalmic – Instilled into the eye (e.g., eye drops for glaucoma).
  Otic – Administered into the ear (e.g., ear drops).

 Nasal – Sprayed or instilled into the nasal cavity (e.g., decongestant

sprays).

4. Inhalational Route

 Pulmonary/Inhalation – Drugs are inhaled into the lungs using

nebulizers, inhalers, or dry powder devices (e.g., bronchodilators for
asthma).

Different Types of Parenteral Routes

Parenteral drug administration refers to injecting the drug directly into

the body, bypassing the digestive system. This is useful for rapid action,
patients unable to take oral medications, and drugs that degrade in the GI
tract.

1. Intravenous (IV) Route

 Definition: The drug is injected directly into the vein.

 Examples: IV fluids, antibiotics (e.g., ceftriaxone), chemotherapy

drugs.

 Advantages:
✅ Rapid onset of action.
✅ 100% bioavailability.
✅ Suitable for large volumes of fluids.

 Disadvantages:
❌ Requires professional administration.
❌ Risk of infection and phlebitis.

2. Intramuscular (IM) Route

 Definition: The drug is injected into a muscle (usually the deltoid,

gluteus, or thigh).

 Examples: Vaccines (e.g., tetanus, COVID-19), analgesics (e.g.,

diclofenac).

 Advantages:
✅ Faster absorption than oral but slower than IV.
✅ Suitable for depot (slow-release) preparations.
  Disadvantages:
❌ Painful administration.
❌ Limited to small volumes (2-5 mL).

3. Subcutaneous (SC) Route

 Definition: The drug is injected into the fatty tissue under the skin.

 Examples: Insulin, heparin, biologics.

 Advantages:
✅ Slower, sustained release of drugs.
✅ Self-administration possible (e.g., insulin for diabetes).

 Disadvantages:
❌ Limited to small doses (≤1 mL).
❌ Absorption may be slower than IM or IV.

4. Intradermal (ID) Route

 Definition: The drug is injected just under the epidermis, within the
dermis layer of the skin.

 Examples: Tuberculosis (Mantoux test), allergy testing, local

anesthetics.

 Advantages:
✅ Minimal drug dose required.
✅ Useful for diagnostic tests and vaccinations.

 Disadvantages:
❌ Absorption is very slow.
❌ Can cause local skin reactions.

5. Intrathecal (IT) Route

 Definition: The drug is injected directly into the cerebrospinal fluid

(CSF) via the spinal canal.

 Examples: Anesthetic agents (e.g., spinal anesthesia), chemotherapy

(e.g., methotrexate).

 Advantages:
✅ Bypasses the blood-brain barrier.
✅ Direct action on the central nervous system (CNS).
  Disadvantages:
❌ Requires expert administration.
❌ Risk of infection (meningitis) and nerve damage.

6. Intra-articular Route

 Definition: The drug is injected directly into a joint.

 Examples: Corticosteroids (e.g., hydrocortisone) for arthritis.

 Advantages:
✅ Direct action on inflamed joints.
✅ Reduces systemic side effects.

 Disadvantages:
❌ Requires expertise.
❌ Risk of infection or joint damage.

7. Intraosseous (IO) Route

 Definition: The drug is injected directly into the bone marrow.

 Examples: Emergency drug delivery (e.g., epinephrine, fluids in

trauma cases).

 Advantages:
✅ Alternative to IV when veins are inaccessible.
✅ Rapid systemic absorption.

 Disadvantages:
❌ Painful and requires specialized equipment.
❌ Risk of bone infection (osteomyelitis).

8. Intraperitoneal (IP) Route

 Definition: The drug is injected into the peritoneal cavity (abdominal

space).

 Examples: Chemotherapy for peritoneal cancers, dialysis solutions.

 Advantages:
✅ Large surface area for absorption.
✅ Can be used when IV access is difficult.

 Disadvantages:
❌ Risk of peritonitis.
❌ Slower absorption than IV.
2Q Write Advantages & Disadvantages of oral route of drug
administration?

2A Advantages and Disadvantages of Oral and Parenteral Routes of

Drug Administration

1. Oral Route (Enteral Route)

The oral route is the most common and preferred method for drug
administration, where the drug is taken by mouth and absorbed through the
gastrointestinal (GI) tract.

Advantages of Oral Route

✅ Convenient and Easy to Administer – Can be self-administered without

medical assistance.
✅ Non-invasive and Painless – No injections or medical procedures
required.
✅ Cost-effective – Less expensive compared to injections and other routes.
✅ Safer – Reduced risk of infection compared to injectable routes.
✅ Variety of Dosage Forms Available – Includes tablets, capsules, syrups,
and suspensions.

Disadvantages of Oral Route

❌ Slow Onset of Action – Takes time for absorption and effect, especially in
solid dosage forms.
❌ Affected by First-pass Metabolism – Some drugs (e.g., nitroglycerin)
are metabolized in the liver before reaching systemic circulation, reducing
effectiveness.
❌ Poor Absorption in Certain Conditions – Drug absorption can be
affected by food, stomach acid, enzymes, or disease conditions.
❌ Unsuitable for Unconscious or Vomiting Patients – Requires
swallowing ability and functioning GI tract.
❌ Not Suitable for Some Drugs – Proteins and peptides (e.g., insulin) get
degraded by stomach acids and enzymes.

2. Parenteral Route (Injectable Route)

Parenteral drug administration involves the delivery of drugs through

injections, bypassing the GI tract.

Advantages of Parenteral Route

✅ Rapid Onset of Action – Especially IV injections, which provide

immediate drug effects (e.g., emergency medications).
✅ 100% Bioavailability (IV Route) – No first-pass metabolism; full dose
reaches systemic circulation.
✅ Suitable for Unconscious or Vomiting Patients – Can be given when
oral administration is not possible.
✅ Allows Administration of Large and Irritating Drugs – Suitable for
drugs that cannot be given orally (e.g., chemotherapy, antibiotics).
✅ More Precise Dosage Control – Ensures accurate dosing, especially in
critical conditions.

Disadvantages of Parenteral Route

❌ Requires Trained Personnel – Needs expertise for administration,

increasing healthcare costs.
❌ Painful and Invasive – May cause pain, discomfort, and patient anxiety.
❌ Risk of Infections – Higher chances of infections due to needle use (e.g.,
IV site infections, abscess formation).
❌ More Expensive – Requires sterile formulations, medical equipment, and
professional administration.
❌ Difficult to Reverse – Once injected, the drug cannot be removed,
increasing the risk of adverse effects.

Comparison Summary

Feature Oral Route Parenteral Route

Ease of Requires trained

Easy, self-administrable
Administration personnel

Onset of Action Slow Fast (IV is immediate)

Feature Oral Route Parenteral Route

Affected by first-pass
Bioavailability 100% (IV)
metabolism

Patient Comfort Painless, non-invasive Painful, invasive

Suitability for
Not suitable Suitable
Emergencies

Risk of Infection Low High

Cost Less expensive More expensive

Possible (e.g., vomiting, Irreversible once

Reversibility
antidotes) administered
3Q What is Absorption and Write about different Mechanisms of
drug absorption. Factors affecting drug absorption?

3A Absorption of Drugs

Definition of Absorption

Absorption is the process by which a drug moves from its site of

administration into the bloodstream for systemic circulation. It is the
first step in drug bioavailability and is crucial for determining the onset and
intensity of drug action.

For oral drugs, absorption primarily occurs in the small intestine, while for
parenteral drugs, absorption depends on the site of injection (e.g., muscle,
subcutaneous tissue).

Mechanisms of Drug Absorption

Drugs are absorbed through different mechanisms depending on their

chemical properties (size, solubility, charge) and the site of
administration. The major mechanisms of drug absorption include:

1. Passive Diffusion

 The most common mechanism for drug absorption.

 Drugs move from high concentration (GI tract) to low

concentration (blood) without using energy.

 Lipid-soluble (non-polar) drugs easily pass through the lipid

bilayer of the cell membrane.

 Example: Alcohol, steroids, and anesthetic gases.

2. Facilitated Diffusion

 Similar to passive diffusion but requires a carrier protein to transport

the drug across the membrane.

 Movement is still down the concentration gradient (high to low)

without energy consumption.
  Example: Transport of glucose via GLUT transporters.

3. Active Transport

 Requires carrier proteins and energy (ATP) to move drugs against

the concentration gradient (low to high).

 Important for the absorption of nutrients and essential ions.

 Example: Levodopa (for Parkinson’s disease) is actively transported

into the brain.

4. Endocytosis (Pinocytosis & Phagocytosis)

 Involves the engulfing of large drug molecules into vesicles inside

the cell.

 Pinocytosis: Small molecules (e.g., vitamins, nutrients).

 Phagocytosis: Large particles (e.g., proteins, nanoparticles).

 Example: Vitamin B12 absorption in the intestine via intrinsic factor.

Factors Affecting Drug Absorption

1. Physiochemical Properties of the Drug

 Molecular Size: Smaller drugs absorb faster than larger ones.

 Lipid Solubility: Lipid-soluble drugs cross cell membranes faster

than water-soluble drugs.

 Degree of Ionization: Non-ionized (uncharged) drugs diffuse

easily, while ionized drugs absorb slowly.

 pH and pKa of the Drug: Acidic drugs absorb better in the stomach
(low pH), while basic drugs absorb better in the intestine (high pH).

2. Route of Administration

 Oral Route: Subject to first-pass metabolism in the liver, reducing

absorption.

 Parenteral Route: Bypasses the GI tract, leading to faster absorption

(IV > IM > SC).

 Inhalation Route: Rapid absorption due to a large surface area and

high blood supply in the lungs.
3. Gastrointestinal (GI) Factors

 Gastric Emptying Rate: Faster emptying speeds up drug absorption.

 Presence of Food: Some drugs are better absorbed with food (e.g.,
fat-soluble vitamins), while others are hindered (e.g., tetracyclines with
calcium).

 Enzyme Activity: Digestive enzymes can degrade some drugs before

absorption (e.g., insulin is broken down in the stomach).

4. Blood Flow to the Absorption Site

 Higher blood flow increases absorption (e.g., muscles have more

blood flow than subcutaneous tissue).

 Shock or low perfusion states decrease absorption.

5. Drug Formulation & Dosage Form

 Liquid forms (syrups, suspensions) absorb faster than solid forms

(tablets, capsules).

 Enteric-coated tablets delay absorption until they reach the

intestine.

 Sustained-release formulations provide slow and prolonged

absorption.

6. Disease Conditions

 GI Disorders (Diarrhea, Malabsorption, Gastroparesis) can

reduce absorption.

 Liver Disease affects metabolism, altering drug bioavailability.

 Heart Failure reduces blood flow to the intestines, delaying

absorption.
4Q Define Distribution. Write about different Physiological barriers
for drug distribution with examples?

4A Drug Distribution

Definition

Drug distribution is the process by which a drug is transported from

the bloodstream to various tissues and organs after absorption or
direct administration into circulation. It determines the drug's onset,
intensity, and duration of action.

The extent and rate of distribution depend on factors like blood flow, drug
solubility, plasma protein binding, and physiological barriers.

Physiological Barriers for Drug Distribution

Certain physiological barriers restrict or regulate the movement of drugs

into specific organs or tissues. These barriers are formed by tight junctions
between endothelial cells, efflux transporters, and enzymatic
metabolism.

1. Blood-Brain Barrier (BBB)

 The BBB is a selective barrier that protects the central nervous

system (CNS) by preventing harmful substances from entering the
brain.

 It consists of tight junctions between endothelial cells, astrocytes,

and efflux transporters (P-glycoprotein).

 Only lipid-soluble, small, and non-ionized drugs can pass easily.

 Example:
 o Crosses the BBB: Diazepam (lipophilic), Levodopa (via
transporter).

o Does not cross: Dopamine (hydrophilic), Penicillin (actively

pumped out).

2. Blood-CSF Barrier

 Found in the choroid plexus, this barrier controls drug entry into the
cerebrospinal fluid (CSF).

 It has tight junctions and active efflux pumps that prevent the
entry of many drugs into CSF.

 Example: Some antibiotics like penicillin do not easily penetrate

unless the meninges are inflamed (e.g., meningitis).

3. Placental Barrier

 The placenta acts as a semi-permeable membrane between

maternal and fetal circulation.

 Lipophilic drugs and small molecules cross easily, while large

and ionized molecules are restricted.

 Example:

o Crosses: Alcohol, Warfarin, Morphine, and some antibiotics.

o Restricted: Insulin, Heparin (large molecules).

4. Blood-Testis Barrier

 Protects sperm cells from harmful substances and immune system

attack.

 Formed by tight junctions in Sertoli cells in the testes.

 Example:

o Crosses: Some steroids and lipid-soluble drugs.

o Restricted: Most antibiotics (making testicular infections

difficult to treat).

5. Blood-Retinal Barrier (BRB)

 Protects the eye and retina from harmful substances.

 Composed of tight junctions in retinal endothelial cells.

  Example:

o Restricted drugs: Most antibiotics, making eye infections hard

to treat.

o Crosses: Lipophilic drugs like chloramphenicol.

5Q Define Biotransformation. Discuss the Phase-I & Phase-II drug

metabolism with examples?

5A Biotransformation (Drug Metabolism)

Definition

Biotransformation is the process by which drugs are chemically altered

in the body to facilitate their elimination. It primarily occurs in the
liver, but other organs like the kidneys, lungs, and intestines can also
contribute. The primary goal of metabolism is to convert lipid-soluble
drugs into more water-soluble metabolites for easier excretion.

Phases of Drug Metabolism

Drug metabolism occurs in two phases: Phase I (Functionalization

Reactions) and Phase II (Conjugation Reactions).

1. Phase-I Reactions (Functionalization Reactions)

 These reactions introduce or unmask functional groups (-OH, -

NH₂, -SH) in the drug molecule.

 It activates, inactivates, or prepares the drug for Phase II

metabolism.

 Enzymes involved: Cytochrome P450 (CYP) enzymes (mainly in

the liver).

Types of Phase-I Reactions

Reaction
Description Example
Type

Addition of oxygen or removal of

Oxidation Diazepam → Oxazepam
hydrogen.

Addition of hydrogen or removal Chloramphenicol → Active

Reduction
of oxygen. metabolite

Breakdown of ester or amide

Hydrolysis Aspirin → Salicylic acid
bonds by water.

🔹 Example of Drug Activation (Prodrug Conversion):

 Codeine (inactive) → Morphine (active) via CYP2D6 oxidation.

🔹 Example of Drug Inactivation:

 Lidocaine undergoes oxidation, forming inactive metabolites.

2. Phase-II Reactions (Conjugation Reactions)

 Involves the addition of large, polar molecules to the drug, making

it highly water-soluble for elimination.

 Phase-II reactions mostly lead to drug inactivation.

 Enzymes involved: Transferases (e.g., UGT, GST, SULT).

Types of Phase-II Reactions

Reaction Type Description Example

Addition of glucuronic
Glucuronidation Paracetamol → Glucuronide
acid.

Paracetamol → Sulfate
Sulfation Addition of sulfate.
metabolite

Addition of acetyl Isoniazid → Acetylated

Acetylation
group. metabolite

Addition of a methyl
Methylation Epinephrine → Metabolite
group.
Reaction Type Description Example

Glutathione Detoxifies reactive Paracetamol overdose →

Conjugation metabolites. Glutathione conjugates

🔹 Example of Drug Activation:

 Morphine undergoes glucuronidation to form an active metabolite

(Morphine-6-glucuronide).

🔹 Example of Detoxification:

 Paracetamol metabolism via glutathione conjugation prevents

toxicity.

Clinical Significance of Biotransformation

1. Prodrug Activation: Some drugs require metabolism for activation

(e.g., Enalapril → Enalaprilat).

2. Drug Interactions: CYP enzyme inhibitors (e.g., Ketoconazole) or

inducers (e.g., Rifampin) affect drug metabolism.

3. Toxicity Prevention: Phase-II reactions detoxify harmful metabolites

(e.g., Acetaminophen toxicity is prevented by glutathione).

4. Genetic Variations: Some people metabolize drugs faster/slower due

to genetic differences in CYP enzymes.
6Q What are the different routes of drug excretion?

6A Routes of Drug Excretion

Drug excretion is the process by which drugs and their metabolites are
removed from the body. The primary organs responsible for excretion are the
kidneys, liver, lungs, sweat glands, and intestines. The major routes of
drug excretion are:

1. Renal (Kidney) Excretion (Most Common)

 Primary route for water-soluble drugs and metabolites.

 Drugs are eliminated through urine in three steps:

1. Glomerular Filtration – Small, unbound drug molecules are

filtered in the kidneys.

2. Tubular Secretion – Active transport of drugs into urine.

3. Tubular Reabsorption – Lipophilic drugs may be reabsorbed

back into blood.

🔹 Examples:

 Excreted by kidneys: Aminoglycosides, Penicillins, Metformin

 Reabsorbed drugs: Lipophilic drugs like Diazepam

🔹 Factors Affecting Renal Excretion:

 Kidney function (renal impairment reduces excretion).

 Urine pH (acidic urine favors excretion of weak bases & vice versa).

2. Hepatic (Biliary) Excretion

 Drugs are metabolized in the liver and excreted in bile →

intestines → feces.

 Some drugs undergo enterohepatic circulation, where they are

reabsorbed and re-used, prolonging their action.

🔹 Examples:

 Excreted in bile: Rifampin, Digoxin, Estradiol

 Enterohepatic circulation: Morphine, Contraceptive steroids

🔹 Factors Affecting Biliary Excretion:

 Liver diseases can reduce bile excretion.

 Drugs with high molecular weight are more likely excreted in bile.

3. Pulmonary (Lung) Excretion

 Important for volatile drugs and gases (anesthetics, alcohol).

 Rate of excretion depends on respiration rate and solubility in

blood.

🔹 Examples:

 Excreted via lungs: Nitrous oxide, Alcohol, Halothane

🔹 Factors Affecting Pulmonary Excretion:

 Faster breathing increases excretion.

 Highly soluble gases are excreted slowly.

4. Gastrointestinal (Fecal) Excretion

  Some drugs are directly excreted into the intestines and
eliminated in feces.

 Insoluble drugs or unabsorbed portions of oral drugs are excreted

this way.

🔹 Examples:

 Directly excreted in feces: Heavy metals (Iron, Lead), Barium

sulfate

 Drugs that undergo biliary excretion: Rifampin, Digoxin

5. Salivary and Sweat Gland Excretion

 Minor route of elimination.

 Drugs excreted in sweat may cause skin irritation.

 Drugs excreted in saliva may lead to a metallic taste or reabsorption

after swallowing.

🔹 Examples:

 Excreted in saliva: Lithium, Phenytoin, Metronidazole

 Excreted in sweat: Rifampin, Alcohol

6. Mammary (Breast Milk) Excretion

 Drugs excreted in breast milk can affect nursing infants.

 Mostly lipophilic and weakly basic drugs get excreted.

🔹 Examples:

 Harmful to infants: Tetracyclines, Diazepam, Chloramphenicol

 Safe drugs: Paracetamol, Penicillins

🔹 Factors Affecting Excretion in Milk:

 Higher lipid solubility increases excretion.

 Weak bases accumulate in milk (milk is slightly acidic).

7Q What is Plasma half-life, how is it calculated? Write a short note
on first order kinetics and zero order kinetics.

7A Plasma Half-Life (t½)

🔹 Definition:
Plasma half-life (t½) is the time required for the concentration of a
drug in the plasma to decrease by 50% after administration. It is an
essential parameter in pharmacokinetics, determining dosing intervals and
drug elimination.

🔹 Factors Affecting Half-Life:

✅ Drug metabolism and elimination rate
✅ Distribution in body tissues
✅ Renal and hepatic function

Calculation of Plasma Half-Life

For drugs following first-order kinetics, half-life is calculated using the

formula:

t1/2=0.693×VdClt_{1/2} = \frac{0.693 \times V_d}{Cl}

Where:
✔ t½ = Half-life
✔ Vd = Volume of distribution
✔ Cl = Clearance
✔ 0.693 = Natural logarithm of 2 (ln2)

First-Order Kinetics vs. Zero-Order Kinetics

🔹 First-Order Kinetics

✅ Definition: Drug elimination is proportional to its plasma concentration.

Higher drug levels lead to a faster elimination rate.
✅ Characteristics:
✔ A constant fraction of drug is eliminated per unit time.
✔ Follows an exponential decline in drug concentration.
✔ Most drugs follow first-order kinetics (e.g., paracetamol, antibiotics).
✅ Graph: Curved line on a plasma concentration vs. time plot.

🔹 Zero-Order Kinetics

✅ Definition: Drug elimination occurs at a constant rate, independent of

drug concentration.
✅ Characteristics:
✔ A fixed amount of drug is eliminated per unit time.
✔ Seen when drug metabolism pathways become saturated.
✔ Examples: Phenytoin, ethanol, aspirin (at high doses).
✅ Graph: Straight-line decline in drug concentration vs. time plot.

Key Differences

Parameter First-Order Kinetics Zero-Order Kinetics

Rate of Proportional to drug Constant, independent of

Elimination concentration concentration

Half-Life (t½) Constant Varies with drug dose

Most drugs (e.g., paracetamol, Phenytoin, ethanol, aspirin

Examples
ibuprofen) (high doses)

Graph Exponential decline Linear decline

8Q Write in brief Receptor mediated Mechanisms of drug action.

7A Receptor-Mediated Mechanisms of Drug Action

In pharmacology, receptor-mediated mechanisms refer to the interaction

of drugs with specific cellular receptors, leading to a physiological
response. These receptors are typically proteins present on the cell
membrane, cytoplasm, or nucleus, and they mediate the drug's action by
triggering intracellular signaling pathways.

Types of Receptor-Mediated Drug Actions

1. Agonists

o Bind to the receptor and activate it, mimicking endogenous

ligands.

o Example: Salbutamol (β₂-agonist) stimulates β₂-receptors in

the lungs for bronchodilation.

2. Antagonists

o Bind to the receptor but do not activate it, blocking the action of
endogenous ligands or agonists.

o Example: Propranolol (β-blocker) inhibits β-adrenergic

receptors to lower heart rate.

3. Partial Agonists
 o Bind to the receptor and produce a submaximal response
compared to full agonists.

o Example: Buprenorphine (partial opioid agonist) provides

analgesia with reduced respiratory depression.

4. Inverse Agonists

o Bind to the receptor and produce an effect opposite to that of an

agonist.

o Example: Antihistamines (e.g., Famotidine) act as inverse

agonists at H₂-receptors to reduce gastric acid secretion.

Types of Receptors and Their Mechanisms

1. Ion Channel-Linked Receptors (Ligand-Gated Ion Channels)

o Rapid response by opening or closing ion channels.

o Location: Cell membrane

o Mechanism: Directly regulate ion flow across the membrane

upon ligand binding.

o Response Time: Milliseconds (fastest response)

o Example: GABA_A receptor – Benzodiazepines enhance GABA

activity, increasing chloride influx and causing sedation.

2. G-Protein Coupled Receptors (GPCRs)

o Activate intracellular signaling cascades via second messengers

like cAMP or IP₃/DAG.

o Location: Cell membrane

o Mechanism: Activate intracellular second messenger

systems (cAMP, IP₃/DAG) via G-proteins.

o Response Time: Seconds to minutes

o Example: Adrenergic receptors – Adrenaline activates β-

receptors, increasing cAMP and stimulating cardiac output.

3. Enzyme-Linked Receptors

o Mediate slow but sustained responses via intracellular enzymatic

activation.
 o Location: Cell membrane

o Mechanism: Ligand binding activates intracellular enzymatic

activity (commonly tyrosine kinase) to mediate cell growth,
differentiation, and metabolism.

o Response Time: Minutes to hours

o Example: Insulin receptor (Tyrosine kinase receptor)

facilitates glucose uptake.

4. Intracellular (Nuclear) Receptors

o Lipophilic drugs cross the membrane and directly modulate gene

transcription.

o Location: Inside the cytoplasm or nucleus (not on the cell

membrane).

o Mechanism: Lipophilic (fat-soluble) drugs cross the cell

membrane and bind to nuclear receptors, directly affecting gene
transcription and protein synthesis.

o Response Time: Hours to days (delayed but long-lasting

effects)

o Example: Corticosteroids bind to nuclear receptors to regulate

inflammation-related genes.
9Q Enumerate various factors modifying the drug effects.

9A Factors Modifying Drug Effects

The pharmacological response of a drug can vary significantly among

individuals due to several modifying factors. These factors influence drug
absorption, distribution, metabolism, and excretion, ultimately
affecting drug efficacy and safety.

1. Physiological Factors

1. Age

o Neonates: Immature liver enzymes and kidney function lead to

prolonged drug effects.

o Elderly: Reduced metabolism and excretion increase the risk of

drug accumulation and toxicity.

2. Sex

o Hormonal differences affect drug metabolism and response

(e.g., estrogen influences metabolism of certain drugs).

3. Body Weight and Composition

o Obese patients may require higher lipid-soluble drug doses due

to larger fat stores.
 o Lean patients may have an increased drug response due to
reduced distribution.

4. Genetic Factors (Pharmacogenetics)

o Genetic polymorphisms affect drug metabolism enzymes

(e.g., CYP450 variations impact warfarin metabolism).

5. Circadian Rhythm

o Drug effects may vary at different times of the day (e.g.,

corticosteroids are more effective in the morning due to
circadian cortisol levels).

2. Pathological Factors

1. Liver Diseases

o Reduced metabolism leads to prolonged drug action and

toxicity (e.g., opioids, benzodiazepines).

2. Renal Diseases

o Impaired drug excretion causes accumulation and toxicity

(e.g., aminoglycosides, digoxin).

3. Cardiovascular Diseases

o Altered blood flow affects drug distribution and clearance.

4. Gastrointestinal Diseases

o Conditions like malabsorption syndromes alter drug

absorption (e.g., reduced absorption of oral iron in celiac
disease).

3. Pharmacokinetic Factors

1. Route of Administration

o Oral drugs undergo first-pass metabolism, reducing

bioavailability.

o Parenteral drugs (IV, IM) bypass first-pass metabolism and

provide a rapid effect.
 2. Drug Metabolism (Enzyme Induction/Inhibition)

o Enzyme Inducers (e.g., Rifampicin, Carbamazepine) →

Increase metabolism → Reduce drug levels.

o Enzyme Inhibitors (e.g., Cimetidine, Erythromycin) →

Decrease metabolism → Increase drug effects/toxicity.

3. Drug Excretion

o Drugs eliminated via urine, bile, or feces can be affected by

kidney and liver function.

4. Drug-Related Factors

1. Drug Dose and Frequency

o Higher doses may cause toxicity, while lower doses may be

ineffective.

2. Drug Interactions

o Synergism: Two drugs enhance each other’s effects (e.g.,

Aspirin + Clopidogrel for antiplatelet action).

o Antagonism: One drug reduces the effect of another (e.g.,

Naloxone reversing opioid overdose).

3. Drug Tolerance

o Repeated use reduces drug efficacy (e.g., opioids,

benzodiazepines).

4. Drug Dependence

o Physical or psychological need for a drug (e.g., opioids,

nicotine).

5. Cumulative Effect

o Drugs accumulate when elimination is slower than

administration (e.g., Digoxin toxicity in renal impairment).

5. Environmental and Lifestyle Factors

1. Diet and Food-Drug Interactions

 o Grapefruit juice inhibits CYP3A4, increasing drug toxicity (e.g.,
Statins).

o High-fat meals delay gastric emptying, altering drug

absorption.

2. Smoking and Alcohol Consumption

o Smoking induces CYP1A2, reducing drug efficacy (e.g.,

Theophylline).

o Chronic alcohol use induces metabolism, while acute alcohol

intake inhibits metabolism.

3. Stress and Psychological State

o Placebo effect: Positive response due to patient belief in the

treatment.

o Emotional stress can alter pain perception and drug response.

10Q Define Adverse Drug Reaction. Classify types of Adverse Drug

Reaction’s with different examples?

9A

Adverse Drug Reaction (ADR) – Definition

An Adverse Drug Reaction (ADR) is a harmful, unintended, and

undesired effect of a drug that occurs at normal therapeutic doses used
for prevention, diagnosis, or treatment of diseases. ADR differs from drug
toxicity, which occurs due to overdose.

World Health Organization (WHO) Definition:

"A response to a drug that is noxious and unintended and occurs at doses
normally used in humans for prophylaxis, diagnosis, or therapy of disease, or
for modification of physiological function."

Classification of Adverse Drug Reactions (ADRs)

1. Type A (Augmented) Reactions

 Predictable and related to the pharmacological action of the drug.

 Dose-dependent and common.

 Often preventable by adjusting the dose.

Examples:

 Hypoglycemia due to insulin overdose.

 Bleeding due to excessive warfarin dose.

 Sedation due to high-dose benzodiazepines.

2. Type B (Bizarre) Reactions

 Unpredictable, not related to drug dose or pharmacology.

 Often caused by hypersensitivity or genetic factors.

 Not dose-dependent, and more serious.

Examples:

 Anaphylaxis due to penicillin.

 Stevens-Johnson Syndrome (SJS) due to sulfonamides.

 Angioedema due to ACE inhibitors (e.g., Enalapril, Ramipril).

3. Type C (Chronic) Reactions

 Long-term effects due to prolonged drug use.

 Often due to cumulative toxicity.

Examples:

 Osteoporosis due to long-term corticosteroids.

 Tardive dyskinesia due to prolonged antipsychotic use.

 Nephrotoxicity due to chronic use of aminoglycosides (e.g.,

Gentamicin).
4. Type D (Delayed) Reactions

 Appear after a long period, even after stopping the drug.

 Often related to carcinogenicity or teratogenicity.

Examples:

 Carcinogenicity: Bladder cancer due to chronic

cyclophosphamide use.

 Teratogenicity: Phocomelia (limb defects) due to thalidomide

exposure during pregnancy.

5. Type E (End-of-Treatment) Reactions

 Occur after sudden withdrawal of long-term drugs.

 Due to physiological dependence.

Examples:

 Rebound hypertension after stopping clonidine.

 Seizures after stopping benzodiazepines suddenly.

 Adrenal insufficiency after abrupt steroid withdrawal.

6. Type F (Failure) Reactions

 Occurs when the drug fails to produce the intended therapeutic

effect.

 Can be due to drug interactions, resistance, or poor adherence.

Examples:

 Antibiotic resistance leading to treatment failure in tuberculosis.

 Failure of oral contraceptives due to enzyme induction by

rifampicin.
11Q Write about drug synergism and drug antagonism with
examples.

11A ) 1. Drug Synergism

Definition

Drug synergism occurs when two or more drugs are used together to
produce a greater effect than the sum of their individual effects. This can
help enhance therapeutic action, reduce drug doses, and minimize side
effects.

Types of Synergism

1. Additive Effect

o The combined effect is equal to the sum of individual

effects.

o Example: Aspirin + Paracetamol → Increased analgesic effect.

 2. Potentiation

o One drug enhances the effect of another without having an

effect of its own.

o Example: Clavulanic acid + Amoxicillin → Clavulanic acid inhibits

β-lactamase, making amoxicillin more effective.

3. Supra-additive (True Synergism)

o The combined effect is greater than the sum of individual

effects.

o Example: Sulfamethoxazole + Trimethoprim → Greater

antibacterial action than either drug alone.

o Example: Alcohol + Benzodiazepines → Dangerous CNS

depression.

2. Drug Antagonism

Definition

Drug antagonism occurs when one drug reduces or blocks the effect of
another drug. It is useful in counteracting overdoses, toxicity, and adverse
effects.

Types of Antagonism

1. Competitive Antagonism

o The antagonist competes with the agonist for the same

receptor but does not activate it.

o Example: Naloxone (opioid antagonist) competes with morphine

at opioid receptors to reverse overdose.

2. Non-Competitive Antagonism

o The antagonist binds irreversibly to the receptor, preventing

the agonist from activating it.

o Example: Phenoxybenzamine (α-blocker) irreversibly binds to α-

adrenergic receptors, blocking adrenaline’s effects.

3. Physiological (Functional) Antagonism

 o Two drugs act on different receptors with opposite effects.

o Example:

 Adrenaline (vasoconstrictor) vs. Histamine

(vasodilator) in anaphylaxis treatment.

 Insulin (reduces blood glucose) vs. Glucagon

(increases blood glucose).

4. Chemical Antagonism

o One drug chemically neutralizes another drug.

o Example:

 Protamine sulfate neutralizes heparin (used in

anticoagulant overdose).

 Activated charcoal absorbs poisons to prevent drug

absorption in poisoning cases.

12Q What are dosage forms, classify them and add a brief note on unit dosage forms.
12A Dosage Formulations

Dosage formulations refer to the physical and chemical forms in which a

drug is manufactured and administered to patients for therapeutic effects.

Types of Dosage Forms

Dosage forms can be broadly classified into:

1️Solid Dosage Forms
2️Liquid Dosage Forms (Monophasic and Biphasic)
3️Semisolid Dosage Forms
4️Gaseous Dosage Forms

1. Solid Dosage Forms

🔹 Definition: Solid dosage forms contain active ingredients in a solid-
state, often mixed with excipients to improve stability, absorption, and
patient compliance.

Classification of Solid Dosage Forms:

✅ Tablets – Compressed or molded solid units containing a precise dose.

✅ Capsules – Hard/soft gelatin shells filled with drugs in liquid/powder form.
✅ Powders – Finely divided drug particles, used orally or topically.
✅ Granules – Coarse, larger particles, often used for effervescent
preparations.

Advantages:

✔️Precise dosage control

✔️Long shelf life and stability
✔️Easy handling and transportation

Disadvantages:

❌ Not suitable for patients with swallowing difficulties (elderly, children)

❌ Slower onset of action compared to liquid forms

2. Liquid Dosage Forms

🔹 Definition: These contain one or more active ingredients dissolved

or dispersed in a liquid medium. They can be monophasic (single-phase)
or biphasic (two-phase) systems.

2A. Monophasic Liquids

🔹 Definition: A single-phase liquid system in which the drug is completely

dissolved in a solvent.

Classification:

✅ Syrups – Sweetened, flavored aqueous solutions (e.g., Cough Syrups)

✅ Elixirs – Clear, hydro-alcoholic liquids (e.g., Digoxin Elixir)
✅ Tinctures – Alcoholic extracts of plant/chemical substances
✅ Linctuses – Viscous liquids used for cough relief
✅ Drops – Small-volume liquid preparations for oral, ophthalmic, or nasal use

Advantages:
✔️Faster absorption than solids
✔️Suitable for patients with swallowing difficulties

Disadvantages:

❌ Shorter shelf life (prone to microbial contamination)

❌ Bulky and less convenient to carry

2B. Biphasic Liquids

🔹 Definition: Two-phase liquid systems in which the drug is either

suspended or emulsified in a liquid medium.

Types of Biphasic Liquids:

1️Suspensions – A solid drug is dispersed in a liquid but not dissolved

(e.g., Antacid Suspension).
2️Emulsions – A mixture of two immiscible liquids, one dispersed in the
other using emulsifying agents (e.g., Cod Liver Oil Emulsion).

Advantages of Biphasic Liquids:

✔️Can be used for water-insoluble drugs

✔️Can provide sustained drug release

Disadvantages of Biphasic Liquids:

❌ Prone to separation (requires shaking before use)

❌ Stability issues compared to monophasic liquids

3. Semisolid Dosage Forms

🔹 Definition: Semisolid formulations have both solid and liquid

properties, offering localized drug delivery.

Classification of Semisolid Dosage Forms:

✅ Ointments – Greasy, hydrophobic bases (e.g., Antibiotic Ointment)

✅ Creams – Water-based or oil-based emulsions (e.g., Hydrocortisone Cream)
✅ Gels – Water-soluble, jelly-like preparations (e.g., Diclofenac Gel)
✅ Pastes – Thick preparations with high solid content for protective action
(e.g., Zinc Oxide Paste)

Advantages:
✔️Localized action with minimal systemic absorption
✔️Suitable for external use (skin, mucous membranes)

Disadvantages:

❌ Can be messy and greasy

❌ Shorter shelf life than solid dosage forms