Pimozide: The Opiate Antagonist Hypothesis and Use in Delusions of Parasitosis

Abstract

Introduction: Pimozide, a neuroleptic agent frequentlyused in the treatment of delusions of parasitosis, hasbeen thought to have a better therapeutic efficacy fordelusions of parasitosis than other antipsychotic agentsbecause of its dual effect of blocking opiate as well asdopamine transmission. If so, this may present a problemin patients who are dependent on opiates, whowould undergo withdrawal when given a strong opiateantagonist such as naloxone. Methods and Results: A literaturesearch was conducted and evidence was foundto alleviate these fears that pimozide would precipitateopiate withdrawal. Although no reports of human studieswere found, several studies have shown that withdrawalis not observed when giving pimozide to opiatedependentanimals. Moreover, the bases for the mechanismof pimozide as an opiate antagonist and for the roleof opiate neurotransmission in delusions of parasitosiswere found to be still controversial.