Drug extrapyramidal side-effects or not: is there a dextromethorphan phenotype difference?

A recent hypothesis suggests the possible role of cytochrome P450 2D6 (CYP2D6) polymorphism (involved in the metabolism of a large number of drugs), as a potential risk factor for the development of extrapyramidal side-effects of psychotropic drugs. The CYP2D6 metabolizer phenotype (dextromethorphan test) of 31 drug treated psychiatric adult patients suffering from extrapyramidal side-effects (group 1) and of 31 matched patients without drug side effects (group 2) were compared. In the first group, 13 poor metabolizer patients (41.9 per cent) were found, characterized by a dextromethorphan metabolic ratio > 0.3, and only two patients in the second group (6.4 per cent). These data provide some support for the notion that in subjects in whom CYP2D6 is probably saturated, the risk of drug extrapyramidal side-effects may be increased. In such patients the choice of psychotropic drugs 'without' this risk must be preferred.