Asians CYP2D6 polymorphisms

Risperidone and its active metabolite 9-OH-resperidone are metabolized by CYP2D6. Polymorphic metabolism should be considered in those with side effects at low doses (approximately 40% of African Americans and Asians can have increased side effects from risperidone and other drugs metabolized through CYP2D6). 

Unexpected neurotoxicity from amphetamine and its analogs (e.g. 3,4 methylenedioxymethamphetamine, also known as ecstasy ) as well as interactions with other drugs subject to CYP2D6 polymorphism would likewise be expected to occur more frequently among Africans and Caucasians than in Asians.(112)... 

CYP2D6 polymorphism has differential prevalence and effect among population subgroups. For example, CYP2D6 polymorphisms associated with slow drug metabolism are found in approximately 5% to 10% of Caucasians and 1% to 3% of Hispanics, African Americans, and Asian Americans [10]. 

Banasik M. Parkinsoris disease and CYP2D6 polymorphism in Asian populations a metaanalysis. Neuroepidemiology 2003, 22, 357-361. 

Kaneda Y, Kawamura I, Fujii A, Ohmori T. Serotonin syndrome— potential role of the CYP2D6 genetic polymorphism in Asians. Int J Neuropsychopharmacol 2002 5(l) 105-6. 

Drugs that are metabolized by the cytochrome P-450 (CYP) isoenzymes CYP2D6, CYP2C9, and CYP2C19 also exhibit genetic polymorphisms. An example of CYP2D6 metabolism is debrisoquine. In about 5-10 /o of Caucasians in North America and Europe and about 1% of Asians, 4-hydroxylation of debrisoquine is reduced, and such individuals are at increased risk for toxicity (orthostatic hypotension). Beta blockers (metoprolol and timolol), antiarrhythmic drugs (encainide and flecainide), tricyclic antidepressants... 

Bisoprolol is eliminated about 50% by renal elimination, whereas metoprolol and carvedilol are essentially completely metabolized and undergo extensive hepatic first-pass metabohsm. Both metoprolol and carvedilol are also substrates for the cytochrome P450 2D6, which is known to be polymorphic. Thus the 7% of the white population and 1 % to 2% of the Asian-American and African-American populations who are CYP2D6 poor metabolizers would be expected to have more pronounced effects than anticipated at the usual doses of carvedilol and metoprolol. 

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