Volume 1, Issue 36, 09/22/2009
Which of the eleven UDP-glucuronosyltransferase (UGT) enzymes are most likely to be involved in drug metabolism and thus targets for drug interactions?
The metabolism, distribution and elimination of medications can occur through a number of pathways which can involve the cytochrome P450 (CYP) enzyme system (phase I metabolism), conjugative enzymes such as sulfation and UDP-glucuronosyltransferase (UGT; phase II metabolism), and influx/efflux cell membrane transporters.(1-3) In addition, it is now known that many medications can be influenced by a combination of these pathways, thus influencing their safety and efficacy profiles as well as the pharmacokinetic profiles of other medications. To complicate things further, all of these pathways are known to be subject to genetic polymorphisms, which can contribute to the differences in the pharmacokinetic and pharmacodynamic properties of a particular medication. It is important for the clinician to recognize and appreciate the contribution of these pathways for proper implementation of drug therapy into clinical practice.
As it relates to the metabolism of a medication, the CYP450 enzyme system contributes the most, with CYP3A4 being the most common enzyme used in the metabolism of many medications.(1-3) The second largest contributor to drug metabolism occurs through UGT enzymes.(3) There are currently...
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