Ethnic differences

People who abuse inhalants are found in both urban and rural settings. Adverse socioeconomic conditions, rather than racial or cultural factors per se, account for most reported ethnic differences in rates of inhalant abuse. Native American youths living on reservations typically have higher rates of inhalant abuse than youths both in the general population and among Native Americans who do not live on reservations (Substance Abuse and Mental Health Services Administration 1996). 

First, we are going to briefly review some of the terms used to refer to ethnic differences and to describe the processes that take place when two or more cultural groups come into contact with each other. Second, we will outline some studies that illustrate how cultural aspects can affect, for example, the prevalence of certain disorders, the different ways symptoms are manifested, how therapeutic aid is sought or the efficacy of different forms of treatment. Cultural aspects can determine the appearance of syndromes that are specific to each culture (culture-bound syndromes) or can affect the manifestation of the symptoms that make up the different mental disorders. We will then show how cultural variations have been incorporated into the different systems of classification. Last, we will also detail the current recommendations on including cultural aspects in the diagnoses of mental disorders. 

Ethnic differences in psychotropic drug response and pharmacokinetics... 

It is clear that ethnic differences in response to antipsychotics exist (Emsley et al, 2002 Frackiewicz et al, 1997). Whereas there has been some work examining first-generation antipsychotics (FGAs) (for reviews, see Frackiewicz etal, 1997 Poolsup et al, 2000), there remains a considerable dearth of research that has examined ethnic differences with respect to the second-generation antipsychotics (SGAs). 

Chiu et al, 1992 Lin Finder, 1983 Lin et al, 1988b Potkin et al, 1984 Lin etal., 1989 Ruiz et al, 1996 Jann et al, 1989 Jann etal, 1992 Zhang-Wong etal., 1998). The majority of these studies were carried out with haloperidol. A number of studies examined differences between Caucasians and Hispanics, and African Americans and Caucasians (Midha et al., 1988b Midha etal, 1988a Ruiz et al., 1996). In general these studies provided mixed results. Another noteworthy feature of the research literature is that there appear to be no studies that have considered ethnic differences in pharmacokinetics and response for the depot antipsychotics. This may be an artifact of the low levels of depot prescribing found in the US, China, and Japan. 

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. 

There is little published information that directly examines ethnic differences in olanzapine pharmacokinetics or pharmacodynamics. Indirectly, examining stable... 

As amisulpride has no hepatic metabolism, low protein binding, and is directly excreted in urine, there is little reason to suspect pharmacokinetic ethnic differences. Of course body mass and pharmacodynamic differences might occur, but to date have received little investigative attention. 

Ethnic differences have been shown to influence response to psychotropic medications. Much of the focus on the explanation for such differences has been on drug-metabolizing (CYP) enzymes of the liver and their sway over pharmacokinetic factors. It is now well recognized that differences in the distribution of polymorphic variants of CYP enzymes exist between different ethnic groups. However, within ethnic groups there are considerable inter-individual variations in drug kinetics, which may not be accounted for solely by genetic variation. Responses to pharmacotherapy are multifaceted and involve the interaction of environmental and... 

Xie, H.-G. etal. (2001). Molecular basis of ethnic differences in drug disposition and response. Annu. Rev. Pharmacol. Toxicol., 41, 815-50. 

Wagner etal. (1998) investigated the ethnic differences in antidepressant response to fluoxetine or placebo in 118 depressed, predominantly male, HIVpositive patients (White n = 79, Hispanic n = 17, African American n = 22). Nine Hispanic subjects (53%) dropped out of treatment making the results difficult to interpret. Among completers in the placebo arm, 80% (four out of five) of Hispanic subjects were responders as compared to 36% of African American subjects and 43% of White subjects. 

Opolka, J. L., Rascati, K. L., Brown, C. M., Barner, J. C. et al. (2003). Ethnic differences in use of antipsychotic medication among Texas Medicaid clients with schizophrenia. /. Clin. Psychiatry, 64, 635-9. 

Wagner, G. J., Mague, S. Rabkin, J. G. (1998). Ethnic differences in response to fluoxetine in a controlled trial with depressed HIV-positive patients. Psychiatr. Serv., 9, 239-40. 

Ethnic differences in CYP2D6 have been more thoroughly documented than with the other isoenzyme (Bradford, 2002). Over 70% of Caucasians but only about half of Asians, Sub-Saharan Africans, and African Americans have fully functional CYP2D6 alleles - alleles that code for normal metabolic activity. Approximately 50% of Asian and people of African ancestry have reduced function or nonfunctioning alleles. As a consequence, many older psychotropic medications are metabolized more slowly and plasma levels would be higher. Thus individuals of African and Asian ancestry would have an increased risk of side effects and should receive lower dose for a therapeutic response when compared to Caucasians of European descent (Lin, 2001 Lawson, 2000). 

The clinical significance of this ethnic difference for psychiatry was found later. A study examining lithium tolerability found more side effects in African American patients with high RBC/plasma ratio even when the lithium levels were in the therapeutic range (Strickland etal., 1995). It is not known whether African Americans require lower doses and will respond with lower plasma levels. We do know that African Americans with mood disorders are less likely to be prescribed lithium either as primary treatment or adjunctive therapy (Valenstein etal., 2006 Kilbourne 8c Pincus, 2006). It is unknown as to whether the lack of tolerability at usual therapeutic doses is a factor. 

---