Abstract: We included five randomised controlled trials (RCTs) with 232 participants comparing haloperidol discontinuation with haloperidol continuation. Discontinuation was achieved in all five studies by replacing haloperidol with placebo. The trials' size ranged between 23 and 87 participants. The methods of randomisation, allocation concealment and blinding were poorly reported. Participants allocated to discontinuing haloperidol treatment were more likely to show no improvement in global state compared with those in the haloperidol continuation group (n = 49; 1 RCT; RR 2.06, 95% CI 1.33 to 3.20; very low quality evidence: our confidence in the effect estimate is limited due to relevant methodological shortcomings of included trials). Those who continued haloperidol treatment were less likely to experience a relapse compared to people who discontinued taking haloperidol (n = 165; 4 RCTs; RR 1.80, 95% CI 1.18 to 2.74; very low quality evidence). Satisfaction with treatment (measured as numbers leaving the study early) was similar between groups (n = 43; 1 RCT; RR 0.13, 95% CI 0.01 to 2.28; very low quality evidence). No usable mental state, general functioning, general behaviour or adverse effect data were reported by any of the trials. This review provides limited evidence derived from small, short-term studies. The longest study was for one year, making it difficult to generalise the results to a life-long disorder. Very low quality evidence shows that discontinuation of haloperidol is associated with an increased risk of relapse and a reduction in the risk of 'global state improvement'. However, participant satisfaction with haloperidol treatment was not different from participant satisfaction with haloperidol discontinuation as measured by leaving the studies early. Due to the very low quality of these results, firm conclusions cannot be made. In addition, the available studies did not report usable data regarding the adverse effects of haloperidol treatment. Considering that haloperidol is one of the most widely used antipsychotic drugs, it was surprising that only a small number of studies into the benefit and harm of haloperidol discontinuation were available. Moreover, the available studies did not report on outcomes that are important to clinicians and to people with schizophrenia, particularly adverse effects and social outcomes. Better designed trials are warranted.

Plain-language summary: We ran electronic searches of Cochrane Schizophrenia's trial register, most recently on 24 January 2019, for trials that randomised people with schizophrenia and are stable on haloperidol treatment to either discontinue taking haloperidol or to continue taking haloperidol. The review authors found and checked 54 records. Five trials met the review requirements and provided usable data. The evidence currently available from randomised controlled trials is of very low quality and suggests that haloperidol discontinuation is associated with poorer outcomes for people with schizophrenia in terms of their overall symptom improvement (global state). It also shows that people discontinuing haloperidol treatment are more likely to experience relapse (reoccurrence of symptoms) during the first year post treatment. There were no trials providing evidence on what happens after the first year. The number of participants leaving the study early (which can be an indication of satisfaction with treatment) was similar between the two treatments. The very low quality of the currently available evidence is due to methodological shortcomings of the included trials. This lowers our confidence in the reliability of results, and hampers their generalisability to real-world situations. It is disappointing that only a small number of studies were identified, and the size and quality of these studies were limited. The evidence available does not enable us to fully answer important questions regarding the effects of discontinuing haloperidol treatment. In particular there is no evidence available related to the side effects of haloperidol. New trials of better quality are needed.