The Effects of Coadministration of Haloperidol and Bethanechol on Plasma Haloperidol and Reduced Haloperidol Concentrations

Haloperidol과 bethanechol 병합사용시 혈장 haloperidol 및 reduced haloperidol 농도에 미치는 영향

Bethanechol, a cholinergic agonist, has been recommended for the management of peripheral anticholinergic side effects during the treatment of antipsychotic medications. But there have been few studies which have evaluated the drug interactions of antipsychotics and bethanechol, even the treatment effects of bethanechol on anticholinergic side effects. So the authors have evaluated whether psychopathology and plasma haloperidol and reduced haloperidol concentrations are significantly changed or not when bethanechol was administrated with maintained doses of haloperidol and other coadministrated drugs(such a benztropine). Also we have evaluated the abating effects of bethanechol on anticholinergic side effects during the treatment with haloperidol. Fifteen schizophrenics with higher than 5 of total score of anticholinergic side effects of 'Rating scale for side effect' were assigned to two groups, and bethanechol 30mg/day and 60mg/day were applied on each group for 4 weeks. The daily haloperidol dosages were fixed before 2 weeks of study. We assessed anticholinergic side effects by 'Rating scale for side effect' and psychopathology by BPRS, and plasma haloperidol and reduced haloperidol concentrations by HPLC at baseline, 2nd week and 4th week. The results were as followed, 1) there was no significant change of plasma haloperidol and reduced haloperidol concentration, 2) at baseline, the dosage of haloperidol showed significant correlation with the total score of anticholinergic side effect, but not at 2nd week and 4th week, 3) in 60mg/day group, dry mouth and the total score of anticholinergic side effects were significantly improved, but not in 30mg/day group, 4) there was no significant change of BPRS except withdrawal at 2nd week. These results suggest that coadministration of bethanechol influenced neither on psychopathology nor on plasma haloperidol and reduced haloperidol concentrations and that improved dry mouth and total score of anticholinergic side effects at 60mg/day.