Co-administration of haloperidol and drugs affecting the angiotensin pathway: Effect on the extrapyramidal system

The present study investigates the extrapyramidal effects of co-administration of enalapril (angiotensin-converting enzyme inhibitor) or losartan (angiotensin receptor blocker) with haloperidol in mice. Enalapril/losartan (as a suspension in 1% gum acacia) was administered by oral gavage and haloperidol was administered as an intraperitoneal injection to all the animals for seven days. Catalepsy was measured 30min after the administration of haloperidol (1mg/kg i.p.) on days 1 and 7. Observations on day 1 constituted the acute study (single dose administration) and observations on day 7, constituted the chronic study (repeated dose administration). Both acute and chronic administration of enalapril/losartan produced an increase in the duration of haloperidol induced catalepsy at the highest dose (20mg/kg). Enalapril produced a more pronounced increase in the duration of catalepsy as compared to losartan on both acute and chronic administration. Results of our study suggest that co-administration of anti-psychotics and drugs affecting the angiotensin system can lead to an increase in motor side effects and therefore should be used with caution in patients with these co-morbid conditions.