Pimozide is a drug developed in the 1960s for the treatment of schizophrenia or related psychoses such as delusional disorder. Previously, pimozide has been advocated as the preferred drug treatment for people with delusional disorder and it has been claimed to be particularly effective for one subtype; mono-symptomatic hypochondriacal psychosis. It has also been claimed that pimozide can help symptoms such as apathy, poor volition and slow and 'impoverished' thinking.
We systematically searched for all known randomised controlled trials comparing pimozide with other antipsychotic drugs, placebo or no treatment for people with schizophrenia or related psychoses. Results suggest pimozide is probably as effective as other commonly used typical antipsychotic treatments based on the outcomes of mental state, relapse, leaving the study early and global functioning. No studies included people with a specific diagnosis of delusional disorders and therefore we cannot comment on pimozide's efficacy for this group of people. Previous concerns regarding adverse effects on the heart were not supported by data from this review, although this may be because the studies were small and short, and the majority of participants did not receive doses above present recommended limits. Pimozide may also be less prone to cause sleepiness than typical antipsychotic drugs, although this benefit has to be balanced against its greater propensity to cause tremor.
Outcome data were often poorly reported with the result that some data could not be utilised in this review. Furthermore, global state outcomes were often reported using 'last observation carried forward' and the effect of this method is unknown but does introduce a risk of a biased data set. Another problem was that 'relapse' was reported quite often without clear definition.