General Pharmacology

Question 1

What is drug biotransformation?

Answer 1

Drug metabolism to allow drugs to become inactive or by increasing excretion by making them more hydrophilic, or by metabolising them to less active agent.

Question 2

Describe phase 1 and phase 2 reactions.

Answer 2

Phase 1 reactions convert the parent drug to a more polar metabolite by introducing or unmasking a functional group (-OH, -NH2, -SH).

This includes oxidation, deamination, hydrolysis, reductions.

Phase 2 reactions involve conjugation of phase I products with an endogenous substrate (such as glucuronic acid, sulfuric acid, acetic acid, or an amino acid) to form a highly polar conjugate.

Question 3

What factors determine the volume of distribution of a drug?

Answer 3

1. Drug factors - lipid solubility, pH, pKa, protein binding
2. Patient factors - age, gender, comorbid disease (e.g. oedema or ascites), body fat, blood flow to tissues