THIRD BHMS
PHARMACOLOGY QUESTION BANK
question bank according to CBDC syllabus
M - MCQ | S - SAQ | L - LAQ | V - VIVA/PRACTICAL | Ø - NON
PHARMACOKINETICS
1. Introduction to Pharmacokinetics
a. Definition
-Pharmacokinetics is the branch of pharmacology that deals with the quantitative study of the absorption, distribution, metabolism, and excretion (ADME) of drugs in the body.
-It explains how the body affects a drug from the time it is administered until it is completely eliminated.
b. Importance in Drug Action
-Determines the onset, intensity, and duration of a drug’s effect.
-Helps in selecting the appropriate dose, route, and dosing interval.
-Ensures that drug levels remain within the therapeutic range to achieve maximum efficacy with minimal toxicity.
-Aids in understanding individual variations in drug response due to factors like age, disease, or genetics.
-Forms the scientific basis for rational and safe drug therapy.
2. Absorption, Distribution, Metabolism, and Excretion of Drugs(ADME)
A] Absorption of Drugs
1. Physicochemical Properties of Drugs
-Lipophilicity: Enhances crossing of cell membranes and distribution into fatty tissues.
-Polarity: Limits drug penetration into lipid-rich membranes.
2. Routes of Administration
-Oral, parenteral, topical, inhalational, sublingual, rectal, etc.
-Influence of route on absorption rate and bioavailability.
3. Gastrointestinal (GI) Factors
-pH of stomach or intestine: Affects ionization and solubility.
-Gastric emptying time and motility: Influences absorption rate.
-Presence of food: May enhance or reduce absorption.
4. Drug Formulation
-Immediate-release vs. sustained-release preparations.
-Enteric coating to protect against stomach acid degradation.
B] Distribution of Drugs
1. Blood Flow to Tissues
-Highly perfused organs (brain, liver, kidney) receive drugs rapidly.
-Poorly perfused tissues (fat, bone) show slower distribution.
2. Plasma Protein Binding
-Albumin: Binds acidic drugs.
-α1-acid glycoprotein: Binds basic drugs.
-Only free (unbound) drug is pharmacologically active
3. Tissue Binding
-Certain drugs accumulate in specific tissues:(e.g., tetracyclines in bones/teeth, lipophilic drugs in adipose tissue)
4. Special Barriers
-Blood-Brain Barrier (BBB): Permits lipophilic and small molecules; restricts polar drugs.
-Placental Barrier: Partial protection; some drugs can cross.
C] Metabolism of Drugs (Biotransformation)
1. Sites of Metabolism
-Liver: Primary organ for metabolism.
-Other sites: Kidneys, lungs, intestines.
2. Phase I Reactions (Functionalization)
-Include oxidation, reduction, and hydrolysis.
-Mainly mediated by cytochrome P450 (CYP450) enzymes.
3. Phase II Reactions (Conjugation)
-Include glucuronidation, sulfation, acetylation, methylation.
-Increase water solubility for excretion.
4. First-Pass Metabolism
-Drug metabolized in liver before reaching systemic circulation.
-Reduces bioavailability (e.g., nitroglycerin, propranolol).
5. Enzyme Induction and Inhibition
-Inducers: (e.g., rifampin, phenobarbital) ↑ metabolism → ↓ drug levels.
-Inhibitors: (e.g., ketoconazole, grapefruit juice) ↓ metabolism → ↑ drug levels.
6. Genetic Polymorphisms
-Variations in metabolic enzymes (e.g., CYP2D6, CYP2C19) affect metabolism rate.
D] Excretion of Drugs
1. Primary Routes of Excretion
a) Renal Excretion (major):
 –Glomerular filtration (filters free drug).
 –Tubular secretion (active process).
 –Tubular reabsorption (pH-dependent).
b) Biliary Excretion:
 –High molecular weight drugs; possible enterohepatic recycling.
2. Other Routes
-Lungs (volatile drugs), sweat, saliva, breast milk.
3. Factors Affecting Pharmacokinetics(ADME)
A] Factors Affecting Absorption
a) Drug-related:
 –Solubility (lipophilic drugs absorb better).
 –Ionization (non-ionized forms cross membranes easily).
 –Molecular size (smaller molecules absorb faster).
 –Formulation (liquid > capsule > tablet).
 –Chemical stability (acid/enzymatic degradation reduces absorption).
b) Route of administration:
 –Oral absorption depends on GI environment.
c) GI factors:
 –pH, gastric emptying, presence of food.
d) Drug transport mechanisms:
 –Passive diffusion, active transport, facilitated diffusion, endocytosis.
B] Factors Affecting Distribution
a) Blood flow to tissues.
b) Plasma protein binding (only free drug is active).
c) Tissue binding (e.g., tetracyclines in bone).
d) Special barriers (BBB, placental).
C] Factors Affecting Metabolism
a) Enzyme activity:
 –Induction (e.g., rifampin, carbamazepine).
 –Inhibition (e.g., ketoconazole, grapefruit juice).
b) Genetic variability:
 –Polymorphisms in CYP enzymes (CYP2D6, CYP2C19).
c) First-pass metabolism:
 –Extent of hepatic or intestinal metabolism.
d) Age:
 –Neonates: Immature enzymes.
e) Age:
 –Elderly: Reduced metabolic activity.
D] Factors Affecting Excretion
a) Route of excretion:
 –Renal, biliary, pulmonary, etc.
b) Drug properties:
 –Lipophilicity (requires metabolism for excretion).
 –Ionization (ionized drugs excreted more easily).
c) Renal function:
 –Impairment reduces clearance.
d) Hepatic function:
 –Liver disease reduces biliary excretion.
e) Age:
 –Neonates and elderly have reduced excretory capacity.
f) Gender: Hormonal variations affect excretion.
g) Genetic variations:
 –Influence metabolic and excretory enzymes.
h) Disease states:
 –Liver, kidney, or heart failure alter ADME.
E] Patient-Related Factors
a) Drug–drug interactions:
 –Competition for enzymes, binding sites, or transporters.
b) Lifestyle factors:
 –Diet (grapefruit juice inhibits CYP enzymes).
 –Smoking/alcohol use (induces CYP1A2).