Reported allergies to antipsychotic agents in a long-term psychiatric hospital.

The incidence of allergic reactions to antipsychotic agents is not well known but would be expected to be low. However, pharmacy records at a large state psychiatric hospital indicated surprisingly high rates of such allergies. We hypothesized that these high rates of reported allergies in the pharmacy database would not be supported by clinical history, but rather that they represented other side effects or past uncritical acceptance of casual patient reports. Method. Patients listed as having experienced allergies to antipsychotic medications were interviewed by two psychiatrists and any clinical evidence that suggested an allergy was noted. Results. Of 585 patients who were hospitalized on the day the data were reviewed, 138 patients (23.6%) were identified by the pharmacy as allergic to an antipsychotic medication, 79 of whom were available and consented to be interviewed. Of these 79 patients, 7 (8.9%) provided evidence of a true allergy and 12 (15.2%) provided evidence that suggested a remote possibility of an allergy. Of the 60 "allergic" patients who provided no evidence of an allergy, 57% reported a non-allergic adverse drug reaction (ADR) that may have accounted for the allergy assignment and 32% reported possible symptoms that might have done so. Length of stay was possibly associated with an unsupported allergy designation (p <0.07). Reported allergies to other psychotropic agents (p <0.02) or to nonpsychotropic agents (p <0.07) were associated with evidence of a "true" allergy to an antipsychotic agent. Conclusions. Allergies to antipsychotic medications may be much less common than suggested by clinical records. The examination of focused clinical histories from patients who have been reported to experience such "allergies" would likely expand the pool of available medications for many patients.