Prospective cytochrome P450 phenotyping for neuroleptic treatment in dementia.

Older patients have more adverse experiences when treated with psychotropics than younger patients. Age-associated physiological changes, such as reductions in hepatic mass and blood flow, magnify genetic and acquired variations in drug metabolism. Cytochrome P450 2D6 (debrisoquine hydroxylase), which is responsible for the metabolism of several antidepressants and neuroleptics, is constitutionally deficient in up to 10 percent of the population. In this study of 45 elderly patients suffering from dementia and treated with perphenazine, 5 patients who were prospectively identified as poor P450 2D6 metabolizers had significantly greater side effects than the 40 extensive metabolizers.