The Influence of Substance Use on Side Effects of Olanzapine, Quetiapine, Risperidone, and Ziprasidone in Psychosis

Side effects restrict the optimal use of antipsychotics. Little is known about the influence of substance use on side effects. The aim of this study was to compare antipsychotic side effects in patients with psychosis with and without substance use, while also taking medication history and diagnosis into consideration.

All patients (n = 226, mean age 34, females 33%) diagnosed with schizophrenia spectrum disorders (SSD; F20-F29) or other psychosis (F30-F32; F10-F19), were treated with olanzapine, quetiapine, risperidone or ziprasidone, and were assessed at baseline, 4-weeks, 14-weeks, and 27-weeks. The UKU-Side Effects Self-Rating Scale version was used to evaluate the side effect profiles, and the information on substance use was based on the Clinician Drug Use Scale.

At baseline, 30% of the patients used substances, 54% were diagnosed with SSD, and 47% were antipsychotic naïve. The occurrence of side effects in total was not different in patients with substance use compared to without after 4-weeks of treatment, nor in the follow-up period. At 4-weeks there were some group differences in relation to substance use, diagnosis, and medication history for single side effects. Patients with substance use showed more increased dream activity, less reduced salivation, and more gynecomastia. Patients with SSD showed less neurological side effects, orgasm dysfunction, and tension/inner unrest. The medication naïve patients showed increased hypokinesia/akinesia.

Substance use alone does not influence the general magnitude of side effects of antipsychotic medication and does not indicate a different prescription practice in patients with psychosis and substance use.