JNTU B.Pharmacy IV BIOPHARMACEUTICS AND PHARMACOKINETICS Previous Question Paper (March-2021 - R17)

i) Biopharmaceutics is the study of the interrelationship between the physicochemical properties of the drug, the dosage form in which the drug is given, and the route of administration on the rate and extent of systemic drug absorption.

ii) Pharmacokinetics is the study of the time course of drug absorption, distribution, metabolism, and excretion (ADME) in the body.

iii) Pharmacodynamics refers to the study of the biochemical and physiological effects of drugs on the body and their mechanisms of action.

iv) Drug disposition encompasses the processes of drug distribution, metabolism, and excretion that occur after the drug enters the systemic circulation.

v) Drug elimination is the irreversible removal of the drug from the body, occurring primarily through biotransformation (metabolism) and excretion.

The Biopharmaceutical Classification System (BCS) categorizes drugs based on their aqueous solubility and intestinal permeability, which are the two critical factors governing oral drug absorption. The system classifies drugs into four classes:

• Class I (High Solubility, High Permeability): These drugs are well-absorbed and their absorption rate is usually limited by the gastric emptying rate. Example: Propranolol, Metoprolol.
• Class II (Low Solubility, High Permeability): The absorption of these drugs is limited by their dissolution rate. Example: Ibuprofen, Glibenclamide.
• Class III (High Solubility, Low Permeability): These drugs show rapid dissolution, but their absorption is limited by the permeability of the intestinal membrane. Example: Cimetidine, Atenolol.
• Class IV (Low Solubility, Low Permeability): These drugs have poor oral bioavailability and present significant challenges for formulation development. Example: Furosemide, Taxol.

This classification helps in predicting the in vivo performance of oral dosage forms and allows for the use of biowaivers for certain drug products.