BACKGROUND Self-injurious behaviour among people with intellectual disability is relatively common and often persistent. Self-injurious behaviour continues to present a challenge to clinicians. It remains poorly understood and difficult to ameliorate despite advances in neurobiology and psychological therapies. There is a strong need for a better evidence base in prescribing and monitoring of drugs in this population, especially since none of the drugs are actually licensed for self-injurious behaviour. OBJECTIVES To determine clinical effectiveness of pharmacological interventions in management of self-injurious behaviour in adults with intellectual disability. SEARCH METHODS We searched the following databases on 19 February 2012: CENTRAL, MEDLINE, EMBASE, PsycINFO, CINAHL, Science Citation Index, Social Science Citation Index, Conference Proceedings Citation Index - Science, Conference Proceedings Citation Index - Social Science and Humanities, ZETOC and WorldCat. We also searched ClinicalTrials.gov, ICTRP and the reference lists of included trials. SELECTION CRITERIA We included randomised controlled trials that examined drug interventions versus placebo for self-injurious behaviour (SIB) in adults with intellectual disability. DATA COLLECTION AND ANALYSIS Two review authors independently extracted data and assessed risk of bias for each trial using a data extraction form. We present a narrative summary of the results is presented. We did not consider meta-analysis was appropriate due to differences in study designs, differences between interventions and heterogeneous outcome measures. MAIN RESULTS We found five double-blind placebo-controlled trials that met our inclusion criteria. These trials assessed effectiveness and safety of drugs in a total of 50 people with intellectual disability demonstrating SIB. Four trials compared the effects of naltrexone versus placebo and one trial compared clomipramine versus placebo.One of the naltrexone versus placebo trials reported that naltrexone had clinically significant effects (≥ 33% reduction) on the daily rates of three of the four participants' most severe form of SIB and modest to substantial reductions in SIB for all participants; however, this study did not report on statistical significance. Another trial reported that naltrexone attenuated SIB in all four participants, with 25 mg and 50 mg doses producing a statistically significant decrease in SIB (P value < 0.05). Another trial (eight people) indicated that naltrexone administration was associated with significantly fewer days of high frequency self injury and significantly more days with low frequency self injury. Naltrexone had different effects depending on the form and location of self injury. Another trial with only 26 participants found that neither single-dose (100 mg) nor long-term (50 and 150 mg) naltrexone treatment had any therapeutic effect on SIB.Comparison of clomipramine versus placebo found no statistically significant benefit for any outcome measure, which included SIB rate and intensity, stereotypy and adverse events. However, it showed clinically significant improvement in the rate and intensity of SIB and stereotypy.There were very few noteworthy adverse events to report in any of the four trials in which these were reported.All trials were at high risk of bias, apart from one trial (Lewis 1996), which was probably at low risk of bias. The short period of follow-up was a significant drawback in the design of all five trials, as it did not allow long-term assessment of behaviour over time.We were unable to examine the efficacy of antidepressants other than clomipramine, antipsychotics, mood stabilisers or beta-blockers as we did not identify any relevant placebo-controlled trials. AUTHORS' CONCLUSIONS There was weak evidence in included trials that any active drug was more effective than placebo for people with intellectual disability demonstrating SIB. Due to sparse data, an absence of power and statistical significance, and high risk of bias for four of the included trials, we are unable to reach any definite conclusions about the relative benefits of naltrexone or clomipramine compared to placebo.