Drug Metabolism

Question 1

Phase 1 metabolism

Answer 1

involves hydrolysis, oxidation or reduction

increases the polarity of the compound and provides an active site for phase 2

mainly carried out by the P-450 family of enzymes: CYP3A4 - found in human liver and metabolises a wide variety of drugs
CYP2D6- metabolises antidepressants, antipsychotics and converts codeine to morphine, reduced/absent expression in 5-10% of people
CYP1A2- induced by smoking and important in the metabolism of theophylline

Question 2

Phase 2 Metabolism

Answer 2

involves conjugation

increases the water solubility of the compound and makes excretion easier

involves the attachment of glucuronic acid, gluthianone, sulphate or acetate to the metabolites created in phase 1

most drugs are inactivated by conjugation, but some drug metabolites may remain active

Question 3

factors which may inhibit or induce drug metabolism

Answer 3

other drugs/substances - enzyme induction, enzyme inhibition

genetics

hepatic blod flow

liver disease

age

sex

ethnicity