2012 Drugs that promote or inhibit coagulation

Answer to example question 2

This question tests: use of cytochrome P450 tables, as well as testing whether you know the active enantiomer of warfarin.

All of these drugs (+ grapefruit juice) interact with CYP3A4.  Only atorvastatin and R-warfarin are substrates of CYP3A4 (eliminating D), and R-warfarin is inactive, meaning that only the efficacy of atorvastatin can be affected (eliminating A,C and E).  Nafcillin is an inducer of CYP3A4, and would reduce the activity of substrates (eliminating F).  Amiodarone and grapefruit juice are inhibitors of CYP3A4, and would increase the efficacy of any substrate, including atorvastatin (so the correct answer is B).

Email: Dr. Janet Fitzakerley | ©2012 University of Minnesota Medical School Duluth | Last modified: 31-may-12 7:25 PM