Drug Interactions Newsletter

Volume 1, Issue 43, 11/10/2009

Question

What are some common medications classified as weak, moderate and strong inhibitors of CYP3A4?

Answer

The cytochrome P450 (CYP) is a well known superfamily of enzymes that are responsible for the oxidative and reductive metabolic transformation of medications used in clinical practice.(1-3)  In addition, the CYP enzymes are commonly associated with causing many clinically relevant drug-drug interactions.  Of the CYP enzymes, CYP3A4 is not only the most prevalent CYP enzyme in the liver, but is used by more than 50% of medications on the market for their metabolism and elimination from the body.(1)  In addition, the CYP3A4 activity can be induced (or accelerated) or it can be inhibited (decreased), thereby changing the drug concentrations present in the body and its pharmacokinetic profile.(1-4)  As it relates to this newsletter issue, the inhibition of CYP3A4 can result in the accumulation of parent drug concentrations that can put the patient at increased risk for side effects and possible toxicity. 

The complete answer to this question also provides a table that summarizes all of the inhibitors of CYP3A4

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