Receptor sensitivity, ethnic differences

With respect to other ethnic groups, African Americans may have a differential sensitivity to weight gain on clozapine (de Leon etal, 2007). They may also require lower doses than Caucasians (Kelly et al, 2006) and inter-individual as well as ethnic responsiveness maybe partly explained by differences in dopamine receptor polymorphisms (Hwang et al, 2005). It is conceivable that side effects may also be differentially expressed based on pharmacodynamic differences resulting from polymorphisms in other receptor types (histaminergic, muscarinic, etc.). This area remains largely unexplored with respect to ethnic differences in antipsychotic side effects. 

Pharmacodynamics is concerned with the effect of a drug on the body, including tissue sensitivity or receptor binding. Pharmacokinetic differences between ethnic groups have received the most study, but pharmacodynamic differences have also been demonstrated. 

Some ethnic differences in therapeutic doses and side effects of various psychotropic medications, including neuroleptics, lithium, and TCAs, have also been explained by pharmacodynamic factors such as tissue or receptor sensitivity (Kalow 1989 Lin et al. 1995 Pi 1998). 

Salzman described a downregulation of benzodiazepine and P-blocker receptors linked to ageing. It has been postulated that Asians have fewer benzodiazepine and P-blocker receptors than Caucasians. Downregulation of these receptors with age (Salzman, 1982) has been described and postulated by Zhou et al. (1990), but hard evidence of racial or ethnic differences is still awaited. If the Chinese are more sensitive to propranolol in spite of their high catabolic rate, it might be linked to adrenergic receptor sensitivity. 

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