Cytochrome p450 Drug Metabolism and Interactions
Oxidative metabolism by cytochrome p450 enzymes is a primary method of drug metabolism. The purpose of drug metabolism is to make drugs more water soluble so they can be more easily excreted from the body. The recent news that Posicor (mibefradil), a newer calcium channel blocker, has been removed from the market due to its high propensity to iteract with other drugs places a spotlight on hepatic drug metabolism.
Drug interactions involving the cytochrome p450 system are common, and generally result from either enzyme inhibition or induction.
Genetic differences are the reason one patient might be susceptible to interactions when another may not. Cytochrome p450 enzymes are often designated by the letters CYP followed by a set of letters and numbers that distinguish enzyme isoforms.
Understanding CYP enzyme interactions might allow prescribers the ability to better anticipate and manage each patient's response to a drug regimen.
University of Colorado Health Sciences Center provides a very good description of Cytochrome pharmacokinetics HERE Note that the Drug Interaction Table referred to on that page is not available.
Attached to this posting are two pdf files containing an abbreviated drug interaction table associated with Cytochrome p450 metabolism.
The abbreviated list shows commonly used drugs affected by CYP interactions. It should be noted that this list is not complete, and that metabolism of some drugs is complex, and may involve more than one enzyme system.
Drug interactions also occur via mechanisms unrelated to CYP enzymatic activity.
Additional information on this topic is in This Psychlinks Posting
Oxidative metabolism by cytochrome p450 enzymes is a primary method of drug metabolism. The purpose of drug metabolism is to make drugs more water soluble so they can be more easily excreted from the body. The recent news that Posicor (mibefradil), a newer calcium channel blocker, has been removed from the market due to its high propensity to iteract with other drugs places a spotlight on hepatic drug metabolism.
Drug interactions involving the cytochrome p450 system are common, and generally result from either enzyme inhibition or induction.
- Enzyme inhibition generally involves competition with another drug for enzyme binding sites, and usually begins with the first dose of the inhibitor. Duration of inhibition corresponds to the half-lives of the respective drugs.
- Enzyme induction occurs when one drug stimulates production of more enzymatic metabolism capacity. The effects of enzyme induction are sometimes more difficult to predict because these are dependent on drug half-lives, the rate of enzyme production, and individual genetic variations.
Genetic differences are the reason one patient might be susceptible to interactions when another may not. Cytochrome p450 enzymes are often designated by the letters CYP followed by a set of letters and numbers that distinguish enzyme isoforms.
Understanding CYP enzyme interactions might allow prescribers the ability to better anticipate and manage each patient's response to a drug regimen.
University of Colorado Health Sciences Center provides a very good description of Cytochrome pharmacokinetics HERE Note that the Drug Interaction Table referred to on that page is not available.
Attached to this posting are two pdf files containing an abbreviated drug interaction table associated with Cytochrome p450 metabolism.
The abbreviated list shows commonly used drugs affected by CYP interactions. It should be noted that this list is not complete, and that metabolism of some drugs is complex, and may involve more than one enzyme system.
Drug interactions also occur via mechanisms unrelated to CYP enzymatic activity.
Additional information on this topic is in This Psychlinks Posting
