Abstract
Drug interactions are known to play a significant role in the incidence of adverse drug reactions (ADRs) both in the community and in hospitals. Both the newer atypical antipsychotics and their more traditional counterparts are subject to drug — drug interactions amongst themselves, with other psychotropics, and with the agents used in the treatment of various physical ailments. The most common interactions encountered in clinical practice are pharmacodynamic in nature. It is well established that antipsychotic drugs reduce the efficacy of levodopa in parkinson's disease by blockade of dopamine receptors in the corpus striatum. The case reported here illustrates a common pharmacodynamic drug interaction of haloperidol with levodopa in a 60-year-old female patient.