Haloperidol versus placebo for schizophrenia

Haloperidol was first developed in the late 1950s. Research subsequently showed its therapeutic effects on the symptoms of schizophrenia, such as hearing voices and seeing things (hallucinations), having strange beliefs (delusions), aggressiveness, impulsiveness and states of excitement. This led to the introduction of haloperidol as one of the first antipsychotic drugs. Antipsychotic drugs are the main treatment for the symptoms of schizophrenia. Despite the introduction of newer antipsychotic drugs (second generation or ‘atypical’ drugs), haloperidol remains in widespread use and is the benchmark for judging the effectiveness of newer antipsychotic drugs.

The aim of this review was to evaluate the effects of haloperidol for schizophrenia and other similar serious mental illnesses compared with ‘dummy’ or no treatment (placebo). A new search for trials was carried out in May 2012 and the review now includes 25 studies with a total of 4651 people. Review authors rated the quality of evidence reported in the trials for seven main outcomes (global state, death, discharge from hospital, relapse, leaving the study early, adverse effects and satisfaction with treatment). For global state, leaving the study early and adverse effects the reviewers rated the evidence as moderate quality, however, relapse and discharge from hospital were rated to be very low quality evidence. There were no data available for death and satisfaction with treatment.

Based on moderate quality evidence, haloperidol was found to be better than placebo in treating schizophrenia. More people given haloperidol improved in the first six weeks of treatment than those given placebo. However, a significant number of people on haloperidol suffered from side effects, including muscle stiffness, uncontrollable shaking, tremors, sleepiness and restlessness.

Authors concluded that haloperidol is a potent and effective antipsychotic for treating the symptoms of schizophrenia but has the potential to cause debilitating side effects. People with schizophrenia and psychiatrists may wish to prescribe a newer antipsychotic drug with fewer side effects.

Finally, a large proportion of other information and data in the trials were poor and badly reported, meaning that better studies are required. Many people, from both groups left the trials early. This suggests that the design and running of the trials was poor and perhaps not acceptable to people. In light of these findings, it is perhaps surprising that haloperidol is a benchmark antipsychotic in widespread use for treating schizophrenia. It is also surprising that haloperidol is widely used as a comparison for new medication. Haloperidol is an effective antipsychotic drug but has serious and debilitating side effects.

Benjamin Gray, Service User and Service User Expert, Rethink Mental Illness.

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 be less favoured as a control drug for randomised trials of new antipsychotics.

Read the full abstract...

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.


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

Search strategy: 

Initially, we 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 2012 update, on 15 May 2012, we searched the Cochrane Schizophrenia Group’s Trials Register.

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 extracted, re-inspected and quality assessed the data. We analysed dichotomous data using risk ratio (RR) and calculated their 95% confidence intervals (CI). For continuous data, we calculated mean differences (MD). We excluded continuous data if loss to follow-up was greater than 50% and inspected data for heterogeneity. We used a fixed-effect model for all analyses. For the 2012 update, we assessed risk of bias of included studies and used the GRADE approach to create a 'Summary of findings' table.

Main results: 

Twenty-five trials randomising 4651 people are now included in this review. We chose seven main outcomes of interest for the 'Summary of findings' table. More people allocated haloperidol improved in the first six weeks of treatment than those given placebo (4 RCTs n = 472, RR 0.67 CI 0.56 to 0.80, moderate quality evidence). A further eight trials also found a difference favouring haloperidol across the six weeks to six months period (8 RCTs n = 307 RR 0.67 CI 0.58 to 0.78, moderate quality evidence). Relapse data from two trials favoured haloperidol at < 52 weeks but the evidence was very low quality (2 RCTs n = 70, RR 0.69 CI 0.55 to 0.86). Moderate quality evidence showed about half of those entering studies failed to complete the short trials (six weeks to six months), although, at up to six weeks, 16 studies found a difference that marginally favoured haloperidol (n = 1812, RR 0.87 CI 0.80 to 0.95). Adverse effect data does, nevertheless, support clinical impression that haloperidol is a potent cause of movement disorders, at least in the short term. Moderate quality evidence indicates that haloperidol caused parkinsonism (5 RCTs n = 485, RR 5.48 CI 2.68 to 11.22), akathisia (6 RCTs n = 695, RR 3.66 CI 2.24 to 5.97, and acute dystonia (5 RCTs n = 471, RR 11.49 CI 3.23 to 10.85). Discharge from hospital was equivocal between groups (1 RCT n = 33, RR 0.85 CI 0.47 to 1.52, very low quality evidence). Data were not reported for death and patient satisfaction.