Pharmaceutical Sciences Flashcards

Which pharmacokinetic parameter describes the fraction of an administered drug dose that reaches systemic circulation unchanged?

Answer: Bioavailability (F)

Bioavailability (F) quantifies the proportion of an administered drug that reaches the systemic circulation, reflecting absorption and first-pass metabolism effects.

What is the primary site of drug metabolism in the body?

Answer: Liver

The liver is the primary organ for drug metabolism, containing abundant cytochrome P450 enzymes that transform drugs into more water-soluble metabolites for excretion.

Which drug formulation property determines whether a tablet should NOT be crushed?

Answer: Extended-release (ER/XR) coating or enteric coating

Extended-release and enteric-coated tablets have specialised coatings that control drug release rate or protect the stomach; crushing destroys this mechanism and can cause toxicity or reduced efficacy.

What is the Henderson-Hasselbalch equation used for in pharmacy?

Answer: Calculating the degree of ionisation of a drug at a given pH

The Henderson-Hasselbalch equation relates pH, pKa, and the ratio of ionised to un-ionised drug, predicting drug absorption and distribution across biological membranes.

Which process describes the elimination of a drug from the body at a constant fraction per unit time, regardless of plasma concentration?

Answer: First-order elimination kinetics

First-order kinetics means a constant percentage of the drug is eliminated per unit time, so the rate of elimination is proportional to the plasma concentration.

Which factor most significantly affects the volume of distribution (Vd) of a highly lipophilic drug?

Answer: Extensive distribution into adipose and peripheral tissues resulting in a large Vd

Highly lipophilic drugs partition extensively into fatty tissues and peripheral compartments, resulting in a large volume of distribution far exceeding actual body water volume.