Background: This retrospective study attempted to replicate the observation that African Americans are more prone to receive excessive doses of antipsychotics, even after variables that have not been well explored in previous studies (smoking and antipsychotic potency) are controlled for.
Method: The populations of 2 neighboring U.S. state hospitals, which were screened for patients who smoked, were included. The total sample comprised 316 patients from the first hospital (surveyed in 1990) and 447 patients from the second hospital (surveyed in 1992) who were taking antipsychotics and were either African American or white. An excessive antipsychotic dose (greater than 1000 mg of chlorpromazine equivalents per day) was the dependent variable in logistic regressions in all patients and in those patients with or without (DSM-III-R) schizophrenia.
Results: In the total sample from both hospitals, excessive dosing was associated with schizophrenia, age under 56 years, long hospitalization duration, high-potency antipsychotics, second hospital, and depot antipsychotics. The odds of being prescribed excessive doses of typical antipsychotics were 1.8 times higher for African American than for white schizophrenic patients. African American race in schizophrenic patients appeared to be associated with the prescription of high-potency antipsychotics and with excessive dosing of this type of antipsychotic. Excessive dosing did not appear to be associated with race in nonschizophrenic patients nor in schizophrenic patients taking low-potency antipsychotics.
Conclusion: Pharmacogenetic differences are not likely to explain this racial difference in prescription of excessive dosing of high-potency antipsychotics, which suggests that clinician attitudes may be a possible explanation. In future studies, pharmacogenetic tests and control for confounding factors, such as smoking, will help to establish whether racial differences in dosing are influenced by different metabolic capacities or physician biases.