Haloperidol versus placebo for schizophrenia

Background: Haloperidol was developed in the late 1950s for use in the field of anaesthesia. Research subsequently demonstrated effects on hallucinations, delusions, aggressiveness, impulsiveness and states of excitement and led to the introduction of haloperidol as an antipsychotic.

Objectives: To evaluate the clinical effects of haloperidol for the management of schizophrenia and other similar serious mental illnesses compared to placebo.

Search strategy: We initially electronically searched the databases of Biological Abstracts (1985-1998), CINAHL (1982-1998), The Cochrane Library (1998, Issue 4), The Cochrane Schizophrenia Group's Register (December 1998), EMBASE (1980-1998), MEDLINE (1966-1998), PsycLIT (1974-1998), and SCISEARCH. We also checked references of all identified studies for further trial citations and contacted the authors of trials and pharmaceutical companies for further information and archive material. For the 2005 update we searched The Cochrane Library (2005, Issue 6).

Selection criteria: We included all relevant randomised controlled trials comparing the use of haloperidol (any oral dose) with placebo for those with schizophrenia or other similar serious, non-affective psychotic illnesses (however diagnosed). Our main outcomes of interest were death, loss to follow up, clinical and social response, relapse and severity of adverse effects.

Data collection and analysis: We evaluated data independently and analysed on an intention-to-treat basis, assuming that people who left the study early, or were lost to follow-up, had no improvement. Where possible and appropriate, we analysed dichotomous data using Relative Risk (RR) and calculated their 95% confidence intervals (CI). If appropriate, the number needed to treat (NNT) or number needed to harm (NNH) was estimated. For continuous data, we calculated weighted mean differences. We excluded continuous data if loss to follow up was greater than 50% and inspected data for heterogeneity.

Main results: Twenty-one trials randomising 1519 people are now included in this review. One new trial, Kane 2002 (n=414) has been added but it did not affect the overall results. More people allocated haloperidol improved in the first six weeks of treatment than those given placebo (3RCTs n=159, RR failing to produce a marked improvement 0.44 CI 0.3 to 0.6, NNT 3 CI 2 to 5). A further eight trials also found a difference favouring haloperidol across the 6-24 week period (8 RCTs n=308 RR no marked global improvement 0.68 CI 0.6 to 0.8 NNT 3 CI 2.5 to 5) but this may be an over estimate of effect as small negative studies were not identified. About half of those entering studies failed to complete the short trials, although, at 0-6 weeks, 11 studies found a difference that marginally favoured haloperidol (11 RCTs n=898, RR 0.8 CI 0.7 to 0.9, NNT 59 CI 38 to 200). Adverse effect data does, nevertheless, support clinical impression, that haloperidol is a potent cause of movement disorders, at least in the short term. Haloperidol promotes acute dystonia (3 RCTs n=93, RR 4.7 CI 1.7 to 44, NNH 5 CI 3 to 9), akathisia (4 RCTs n=333, RR 2.6 CI 1.4 to 4.8, NNH 7 CI 3 to 25) and parkinsonism (4 RCTs n=163, RR 11.7 CI 2.9 to 47, NNH 3 CI 2 to 5).

Authors' conclusions: Haloperidol is a potent antipsychotic drug but has a high propensity to cause adverse effects. Where there is no treatment option, use of haloperidol to counter the damaging and potentially dangerous consequences of untreated schizophrenia is justified. However, where a choice of drug is available, people with schizophrenia and clinicians may wish to prescribe an alternative antipsychotic with less likelihood of adverse effects such as parkinsonism, akathisia and acute dystonias. Haloperidol should not be a control drug of choice for randomised trials of new antipsychotics.