GPAT Biopharmaceutics and Pharmacokinetics Syllabus

Biopharmaceutics and Pharmacokinetics syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Biopharmaceutics and Pharmacokinetics in GPAT, not a summary of it.

1. 1

   Bio-pharmaceutics

   5 topics

   • Introduction to Biopharmaceutics
   • Drug Absorption
   • Drug Distribution
   • Drug Metabolism
   • Drug Excretion
2. 2

   Bio-pharmaceutical Statistics

   3 topics

   • Descriptive Statistics
   • Inferential Statistics
   • Biostatistics in Drug Development
3. 3

   Bio-availability & Bio-equivalence

   4 topics

   • Bioavailability
   • Factors affecting Bioavailability
   • Bioequivalence
   • Regulatory Requirements

Biopharmaceutics and Pharmacokinetics flashcards for GPAT

24 of 50 cards from the Biopharmaceutics and Pharmacokinetics deck — real questions with worked answers.

1. Define biopharmaceutics.

   The study of the relationship between the physicochemical properties of a drug in its dosage form and the route of administration on the rate and extent of systemic drug absorption.

2. What are the two sequential rate processes involved in the in vivo performance of an oral solid dosage form before absorption?

   Disintegration of the dosage form (and dissolution of the drug) followed by drug dissolution into the gastrointestinal fluids; dissolution is usually the rate-limiting step for poorly soluble drugs.

3. State the Noyes-Whitney equation for dissolution rate and what it describes.

   dC/dt = (D·A/h)(Cs − C), where D = diffusion coefficient, A = surface area, h = diffusion layer thickness, Cs = saturation solubility, C = bulk concentration. It describes the rate of drug dissolution.

4. What is the Biopharmaceutics Classification System (BCS) based on, and name its four classes?

   Based on aqueous solubility and intestinal permeability. Class I: high solubility/high permeability; Class II: low solubility/high permeability; Class III: high solubility/low permeability; Class IV: low solubility/low permeability.

5. Define pharmacokinetics.

   The study of the time course of drug absorption, distribution, metabolism, and excretion (ADME) — i.e., what the body does to the drug.

6. What is drug absorption and what is the principal mechanism for most drugs?

   The movement of drug from the site of administration into the systemic circulation. The principal mechanism for most drugs is passive diffusion down a concentration gradient.

7. According to the pH-partition hypothesis, in what form do drugs best cross biological membranes?

   In their unionized (non-ionized), lipid-soluble form, which can passively diffuse across lipid membranes; the ionized fraction is poorly absorbed.

8. Using the Henderson-Hasselbalch equation, write the relationship for a weak acid.

   pH = pKa + log([ionized]/[unionized]) = pKa + log([A⁻]/[HA]). For a weak acid, lowering pH below pKa increases the unionized fraction.

9. Where are weak acids and weak bases best absorbed in the GI tract based on the pH-partition theory?

   Weak acids (e.g., aspirin) are largely unionized in the acidic stomach, but most absorption still occurs in the small intestine due to its large surface area; weak bases are better absorbed in the more alkaline intestine.

10. Name the main mechanisms of drug transport across membranes.

    Passive diffusion, facilitated diffusion (carrier-mediated, no energy), active transport (carrier-mediated, requires energy, can move against gradient), and endocytosis/pinocytosis.

11. What is the difference between active transport and facilitated diffusion?

    Both are carrier-mediated and saturable, but active transport requires energy (ATP) and can move drug against a concentration gradient, whereas facilitated diffusion needs no energy and only moves drug down its gradient.

12. List key factors that influence gastrointestinal drug absorption.

    Gastric emptying rate, GI motility, GI pH, surface area, blood flow (perfusion), presence of food, drug particle size/dissolution, lipophilicity, pKa, and first-pass metabolism.

13. Define drug distribution.

    The reversible transfer of a drug from the systemic circulation into tissues and body fluids after it has been absorbed.

14. Define apparent volume of distribution (Vd) and give its formula.

    Vd is the hypothetical volume of body fluid required to contain the total amount of drug at the same concentration as in plasma. Vd = Amount of drug in body / Plasma drug concentration (Vd = Dose/C0).

15. What does a large volume of distribution (Vd) indicate about a drug?

    That the drug is extensively distributed into tissues (highly lipophilic or tissue-bound) with relatively low plasma concentration; values can far exceed total body water (e.g., digoxin ~500 L).

16. How does plasma protein binding affect drug distribution and action?

    Only free (unbound) drug is pharmacologically active and able to distribute, metabolize, and be excreted. Highly protein-bound drugs have a smaller Vd; acidic drugs bind mainly albumin, basic drugs bind α1-acid glycoprotein.

17. What is the blood-brain barrier and how does it affect distribution?

    A selective barrier of tight-junction endothelial cells that restricts entry of polar/ionized drugs into the CNS; only lipophilic, unionized drugs cross readily by passive diffusion.

18. Define drug metabolism (biotransformation) and its general purpose.

    The enzymatic conversion of a drug into metabolites, generally making it more polar/water-soluble for easier excretion; usually converts active lipophilic drugs to inactive hydrophilic metabolites.

19. Distinguish Phase I and Phase II metabolic reactions.

    Phase I (functionalization): oxidation, reduction, hydrolysis — introduces or unmasks a functional group (mainly via cytochrome P450). Phase II (conjugation): attaches an endogenous polar molecule (e.g., glucuronic acid, sulfate, glutathione) to increase water solubility.

20. Which enzyme system is responsible for most Phase I oxidative drug metabolism?

    The cytochrome P450 (CYP450) microsomal mixed-function oxidase system in the liver, especially the CYP3A4 isoform.

21. What is the most common Phase II conjugation reaction and the enzyme involved?

    Glucuronidation, catalyzed by UDP-glucuronosyltransferase (UGT) using UDP-glucuronic acid as the cofactor.

22. What is the first-pass (presystemic) metabolism effect?

    The metabolism of an orally administered drug in the gut wall and liver before it reaches the systemic circulation, reducing its bioavailability.

23. Define a prodrug.

    An inactive (or less active) compound that is converted by metabolism in the body into the active drug, e.g., enalapril to enalaprilat.

24. What is the difference between an enzyme inducer and an enzyme inhibitor?

    An inducer (e.g., rifampicin, phenobarbital) increases CYP enzyme synthesis, increasing metabolism and decreasing drug levels; an inhibitor (e.g., ketoconazole, erythromycin) decreases enzyme activity, increasing drug levels and toxicity risk.

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