Psychopharmacology

One of the major treatment approaches in mental disorders is the use of psychoactive drug therapies, particularly in the more serious spectrum of disorders. The availability of a large range of modern psychopharmacological agents parallels the widespread and common use of these medications for a variety of conditions related to mental illness. There is now general consensus that the classes of drugs known as antipsychotics and antidepressants are both effective and beneficial in treating underlying symptoms of psychosis and depression, respectively. This applies equally to patients from diverse cultures and ethnicities. Although the exact mechanisms of action are not known, the current understanding is that neurobiological abnormalities are associated with illness states and that such drugs work by altering brain function and chemistry.

The dosing and effects of psychoactive medications are known to vary between individuals from different cultures. For example, Asian patients are found to require lower doses of medications than are Caucasian patients because they appear to be more drug-sensitive. Such ethnic variations in drug responses have increasingly been found in clinical experience, anecdotal reports, surveys, and systematic studies. The emerging field of ethnopsychopharmacology, which has gained recent recognition in the clinical and research arena, examines variability in pharmacological treatments and response across ethnicity, culture, and environment. The emphasis on the issues of culture and race in medication use highlights that treatment outcomes are influenced by both genetic and non-genetic factors, and observed differences found between population groups are caused by biological and environmental factors. There is growing evidence of genetic differences across various ethnic groups that affect both drug metabolism and effects. Consequently, different rates of metabolism for particular medications may result in either rapid or slow excretion of these drugs from the body. In general, Asian and African American subjects are more likely to metabolize certain psychiatric drugs more slowly than do Caucasian subjects. Hence, giving standard doses of medication to drug-sensitive individuals may cause excessive accumulation of the drug, leading to increased risk of side effects and subsequent nonadherence to treatment. Furthermore, environmental and dietary factors, including the use of herbal remedies, also [Page 372]play an important role in the metabolism of medicines for psychiatric conditions.

Despite the widespread use of psychiatric drugs across most cultures and countries globally, there remains a surprising lack of research in this area. Studies have shown that Asian patients receive a lower dose of antipsychotics or have a higher blood level of drugs than do Caucasians for a given dose, although the findings are not always consistent. In terms of antidepressants, comparative cross-ethnic research has shown mixed results, with some studies showing that Asians have slower metabolism of antidepressants than Caucasians, but other studies finding no differences. Moreover, cross-ethnic studies on the effect and use of newer medications are still limited. Comparative findings that are gradually emerging indicate that ethnic differences in medication effects reflect a close interaction among genetic, environmental, and cultural factors.

The principal biological process to eliminate drugs from the body is the metabolism of drugs. The metabolism of antidepressants and antipsychotics mostly involves the drug-metabolizing enzymes in the liver. Large individual and ethnic group variations are found in the activities of these liver enzymes, which can lead to differential drug levels and side effects. These enzymes' activities have been found to correlate with variations in the genetic makeup. These genetic differences show significant heterogeneity in various population groups. Other biological factors that affect drug processing and need to be considered in individualizing drug treatment include body mass, gender, age, pregnancy, and disease states.

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