21 - Ethnic and cultural factors in psychopharmacology

Summary

Summary In this chapter we highlight some key factors of which clinicians need to be aware in practising psychiatry in ethnically diverse populations. These include pharmacodynamic and pharmacokinetic principles, and their application in pharmacological management of psychiatric conditions. Ethnic differences in pharmacodynamics are most clearly demonstrated in the greater sensitivity to a variety of drugs in Whites than in Asians or in African–Caribbeans.

Barring a few exceptions (such as rauwolfia serpentina, a source of reserpine first identified in Asia), most psychiatric medications have been developed in the West, especially the USA, the UK and Europe, and their safety trials have been conducted in these populations. Although these drugs are used all over the world there has been limited research to determine accurate pharmacodynamic and pharmacokinetic profiles across different ethnic groups. Clinicians usually adopt a ‘universalist style’ (seeing every condition and treatment as similar) of managing psychiatric illnesses, but this appears to neglect the information from the emerging literature that advocates a relativist approach to pharmacotherapy (Lin et al, 1995).

A recently recognised key factor in the study of pharmacokinetics is pharmacogenetics: a pharmacogenetic variation according to ethnic group can lead to significant genetically determined modifications of metabolising enzymes (i.e. the pharmacokinetic handling of the drug by the body). This results in differing therapeutic levels and half-lives of drugs and, therefore, variable profiles of their therapeutic and adverse effects. Pharmacogenetic research has uncovered significant differences between ethnic groups related to drug metabolism, clinical effectiveness and side-effect profile (Lee et al, 2008).

In addition to ethnobiological determinants of drug response, there are significant cultural factors: the concurrent use of pluralistic health systems, alternative therapies and folk remedies which might support, hinder or complicate pharmacotherapy and treatment adherence.

Ethnicity

General issues

Ethnicity and culture powerfully determine individual pharmacological responses, which are shaped by both environmental and genetic factors (Lin et al, 2008). Genetic polymorphism in genes encoding drug metabolising enzymes as well as the putative targets of pharmaceutical agents (e.g. neurotransmitters, receptors and transporters) and environmental factors such as diet and smoking are also likely to be affected by ethnicity and culture.