Principles of Drug Metabolism, Action and Use

Question 1

What is the function of xenobiotic metabolizing enzymes?

Answer 1

Convert lipophilic chemicals to more hydrophilic derivatives to aid in their elimination from the body through the urine or bile.

Question 2

A _______ is a compound that requires a phase I reaction to be activated.

Answer 2

prodrug

Question 3

Components of the herbal remedy St. John’s Wart (e.g. hyperforin) and some steroids can induce CYP3A4 expression in the liver, leading to _______ bioavailability of drugs metabolized by the CYP. A. Increased B. Decreased C. No change - only CYP inhibitors affect bioavailability

Answer 3

B

Question 4

Glucuronidated or unconjugated drugs can be reabsorbed into the circulation following metabolism in the liver through either of which two pathways?

Answer 4

1. enterohepatic recirculation pathway
2. direct reabsorption into intestinal epithelial cells

Question 5

Hyperbilirubinemia is a symptom of Type I or Type II Crigler-Najjjar syndromes, which result from reductions in the level of functional __________.

Answer 5

UGT1A1

Question 6

Why does viral protease inhibitor atazanavir contribute to ADRs in people with Gilbert’s syndrome?

Answer 6

Atazanavir inhibitrs UGT1A1, which has a binding site for bilirubin. Gilbert’s syndrome patients have a polymorphism in UGT1A1 and slightly elevated 60-70% increase in circulating bilirubin levels.

Question 7

The conjugation of GSH to a toxic metabolite of ___________, NAPQI, can lead to its inactivation and elimination.

Answer 7

acetominophen - an acetominophen overdose can lead to depletion of cellular GSH and accumulation of toxic levels of NAPQI