Hypothesis of racial differences in effective therapeutic dosage of antipsychotic medications in treating psychotic symptoms

The reasons for the difference between the prescription pattern in African-American and their Caucasian counterparts in above studies [16–18] could not be adequately explained and the observation that minority individuals were likely to be prescribed higher doses of antipsychotic medications did not give a satisfactory answer to why the difference?

Therefore, a possible explanation is that at the same level of severity of psychotic symptoms as measured by any standardized rating scale, African-Americans and black Africans of Sub-Saharan African descent might require a higher dosage of antipsychotic medications compared to their Caucasian counterparts for resolution of their psychotic symptoms. This difference may lie in varied pharmacogenetic effects in metabolism and utilization of antipsychotic medications in different races of the world.

The argument of racial differences as it affects the effective therapeutic dosage of antipsychotic medications in treatment of psychosis is given a further weight by Sim et al study [20], which reported higher dosage of antipsychotic medications prescription pattern in East Asian countries, especially Japan, Korea and Singapore.

There is need to explore the possible explanations for the apparent racial and regional differences in dosage prescription pattern of antipsychotic medications.

Differences in prescribing practices

It had already been noted that prescribing practices might vary from one professional to another and from one region to another [11]. This may be because of variation in training background of individual mental health professionals. It may also be differing practices in different regions of the world which had come to stay because of empirical observation in practice over a long period of time that symptoms resolution of psychosis are delayed or unachievable when the recommended guide lines are strictly adhered to. This may be the possible picture of situation in Sub-Saharan African countries where empirical observation had shown higher dose of antipsychotic medications prescription among mental health professionals compared to the western world.

The possible argument against differences in prescribing practices being a function of training background could be found in literature coming from the United States (US), where training of mental health professionals is regulated by a uniform body and can be presumed to be a uniform training background. In these literatures [16–18], it had been consistently found that African-American are likely to be placed on higher dose of antipsychotic medications and are likely to take same as maintenance medications over a longer period of time compared to their Caucasian counterparts. It could also be argued that the relative higher dosage of antipsychotic medications being prescribed in African-Americans compared to their Caucasian counterparts is borne out of a long standing practicing norms derived from empirical observations, which had not been subjected to evidence based practice approach through carefully controlled studies.

Therefore, the significant difference in dosage prescription pattern and longer term use of antipsychotic medications observed in African-Americans and black Africans in Sub-Saharan Africa compared to their Caucasian counterparts may not be solely explained by variation in training backgrounds of attending mental health professionals in these regions of the world.

Socio-cultural acceptability and unacceptability of the presenting psychotic symptoms

Socio-cultural acceptability of patients with symptoms of mental illness may vary according to symptoms presentation. Patients with depressive symptoms are likely to be more accepted and coped with than patients that present with psychotic symptoms, while patients that present with psychotic symptoms without aggression are tend to be more accepted and coped with than patients that present with psychotic symptoms and aggression.

The socio-cultural acceptability and unacceptability of patients' symptoms affect directly and indirectly the prescription pattern and practices. Famuyiwa [12] noted that there was tendency for patients with depression to be under treated or under medicated, possibly because of high acceptability of these patients compared to those presenting with psychotic symptoms. Sim et al [20] had identified aggression as an important factor positively associated with high dosage prescription of antipsychotic medications in East Asian region. The relevance of socio-cultural acceptability and unacceptability of symptoms presentation as it affects prescription practices is further highlighted from the report of Barbui et al study [21], who found that positive symptoms presentation in patients with schizophrenia was positively associated with high antipsychotic dose prescription, whereas negative symptoms presentation was negatively associated with high antipsychotic dose prescription above recommended prescription guidelines.

Relating Barbui et al [21] findings to the findings of Diaz and De Leon [19] who found that the probability of being prescribed high dose and high potency antipsychotic medications was about two times higher for African-Americans than for Caucasian patients with schizophrenia, one would be tempted to ask whether African-Americans are likely to present with more florid positive symptoms of schizophrenia compared to their Caucasian counterparts. Another plausible explanation is that African-American patients presenting with psychotic symptoms were usually assessed to be more potentially aggressive and dangerous compared to their Caucasian counterparts. These two possibilities may be able to explain the apparent difference in antipsychotic medication dosage prescription pattern for African-Americans and their Caucasian counterparts.

Then, the zeal to curtail aggression and potential dangerousness in a patient presenting with psychotic symptoms may be the reason behind the dosage prescription of antipsychotic medication well above the recommendation in standard prescription guidelines. This may also explain poly-pharmacy and common use of depot antipsychotic medications among African-American and black African patients from sub-Saharan Africa that had been noted in some studies [13, 18–21].

Hypothesis of racial differences in psychotic symptoms response to antipsychotic medications

Another possible explanation for differences in dosage prescription pattern of antipsychotic medications that had been found in the above studies [11, 13, 16–21] is racial differences in psychotic symptoms response to various antipsychotic medications.

Having been established that genetic variation have some influence on pharmacodynamics and pharmacokinetics of psychotropic medications [1–4], there are possibilities that racial differences in genetic make-up may influence the effective therapeutic response to dosage of antipsychotic medications.

The deviation in dosage prescription practices from prescription guidelines published for use in western parts of the world [14, 15] in most Sub-Saharan African countries and the consistent findings of studies coming from the United States [11, 16–19, 21, 22], that documented high dosage prescription of antipsychotic medications among African-American patients compared to their Caucasian counterparts and also the study by Sim et al [20] coming from East Asia give some support to the hypothesis that racial differences in psychotic symptoms response to antipsychotic medications might be responsible for the apparent difference in dosage prescription practices. Although, Diaz and De Leon [19] were quick to conclude that pharmacogenetic differences were unlikely to explain the significant racial difference in dosage prescription pattern of antipsychotic medications found in their study and adduced reason for their finding to clinicians' attitude. However, the argument that clinicians' attitude could be responsible for their finding need to be subjected to further challenge in the presence of growing body of evidence supporting biological and socio-cultural determinants for possible ethnic or racial difference in response to psychotropic medications [1–4, 8–10]. This would explain why the authors themselves [19] recommended pharmacogenetic testing in future studies to unravel the reason for their finding which had been consistently replicated by other studies [11, 16–18, 21, 22].