An isolated report describes acute dystonia in one patient,whichwas attributed to an interaction between metronidazole and chloroquine.
Clinical evidence,mechanism, importance and management
A patient was given a 7-day course of metronidazole and ampicillin,following a laparoscopic investigation. She developed acute dystonic reactions (facial grimacing,coarse tremors, and an inability to maintain posture) on day 6, within 10 minutes of being given chloroquine phosphate (equivalent to 200mg of base) and intramuscular promethazine
25 mg. The dystonic symptoms started to subside within 15 minutes of being given diazepam 5mg intravenously,and had completely resolved within 2 hrs (See reference number 1).
The authors of report attribute dystonia to an interaction between metronidazole and chloroquine as she had taken both drugs alone without adverse effect. However, they do not fully assess possible contribution of promethazine, which is known to cause dystonias. It is therefore possible that reaction seen was an adverse effect of promethazine, or perhaps even an interaction between promethazine and chloroquine. No general recommendations can therefore be made from this single report.
1. Achumba JI,Ette EI, Thomas WOA, Essien EE. Chloroquine-induced acute dystonic reactionsin the presence of metronidazole. Drug Intell Clin Pharm (1988) 22, 308–10.