Volume 1, Issue 37, 10/01/2009
What herbal or natural medicines are known to be inhibitors of cytochrome P450 (CYP) 3A4, thereby increasing the risk for causing clinically relevant drug interactions with many medications?
It is well known that the cytochrome (CYP) P450 enzyme system is involved in drug metabolism of many medications used in clinical practice and have been implicated in the causing clinically relevant drug-drug interactions.(1,2) There are a number of CYP450 enzymes involved in mediating drug interactions and commonly include CYP1A2, 2C9, 2C19, 2D6, and 3A4.(1) Of these 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) If the number and level of complexity were not enough with prescription medications alone, the addition of a growing increase in the use of natural and herbal medicines, which are now known to inhibit CYP enzymes as well, is only going to make it worse.(3) In fact, the number of herbal or natural medicines that are known to inhibit CYP3A4 is growing and is of clinical importance when assessing the potential etiologies in adverse drug events that appear to be from a drug-drug interaction (see the table below).(4-14) As such, all clinicians, regardless of specialty or level of training, need to be aware of the list natural medicines found in the table provided in this issue.
There is a table with this newsletter that summarizes all of the known herbal or natural medicines known to be inhibitors of CYP3A4 (listed by common name and scientific name) a long with the type of inhibition on CYP3A4.
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