This report documents a rare case of delayed-onset multiple acute dystonias after treatment with low dose intramuscular (IM) haloperidol lactate injection in a setting of non-neuroleptic drug overdose. The drug–drug interactions between haloperidol and high levels of paracetamol and naproxen are deliberated upon. A 25-year-old Asian female was admitted after an intentional overdose of medications (paracetamol, naproxen and pregabalin). She received 5 mg of IM haloperidol injection for agitation. 21 hours later she experienced mild intermittent ocular deviation in an upward and outward direction and generalised stiffness, which were self-resolving. An hour later, she required another 2.5 mg of IM haloperidol injection for further agitation. In the 35 hours following her first IM haloperidol (13 hours after the second IM haloperidol), she developed a total of three episodes of oculogyric crisis (OGC) with torticollis. Each episode was treated promptly with IM diphenhydramine 25 mg, and there was remission of symptoms within 15 minutes of treatment. An objective causality assessment revealed a definite relationship between the episodes of acute dystonia with IM haloperidol therapy. Where oral alternatives and IM atypical antipsychotics/benzodiazepines are unavailable, rapid tranquillisation with a high-potency typical antipsychotic is a possibility. However, consideration should be made to combine haloperidol with an anticholinergic agent as prophylaxis against acute dystonia, especially in the setting of drug overdose, even if it is that of a non-neuroleptic drug (in this case, paracetamol and naproxen).
A case of delayed-onset multiple oculogyric crisis and torticollis episodes after low dose intramuscular haloperidol in a non-neuroleptic drug overdose setting