Cannabinoids for nausea and vomiting in adults with cancer receiving chemotherapy

Background Cannabis has a long history of medicinal use. Cannabis‐based medications (cannabinoids) are based on its active element, delta‐9‐tetrahydrocannabinol (THC), and have been approved for medical purposes. Cannabinoids may be a useful therapeutic option for people with chemotherapy‐induced nausea and vomiting that respond poorly to commonly used anti‐emetic agents (anti‐sickness drugs). However, unpleasant adverse effects may limit their widespread use. Objectives To evaluate the effectiveness and tolerability of cannabis‐based medications for chemotherapy‐induced nausea and vomiting in adults with cancer. Search methods We identified studies by searching the following electronic databases: Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, PsycINFO and LILACS from inception to January 2015. We also searched reference lists of reviews and included studies. We did not restrict the search by language of publication. Selection criteria We included randomised controlled trials (RCTs) that compared a cannabis‐based medication with either placebo or with a conventional anti‐emetic in adults receiving chemotherapy. Data collection and analysis At least two review authors independently conducted eligibility and risk of bias assessment, and extracted data. We grouped studies based on control groups for meta‐analyses conducted using random effects. We expressed efficacy and tolerability outcomes as risk ratio (RR) with 95% confidence intervals (CI). Main results We included 23 RCTs. Most were of cross‐over design, on adults undergoing a variety of chemotherapeutic regimens ranging from moderate to high emetic potential for a variety of cancers. The majority of the studies were at risk of bias due to either lack of allocation concealment or attrition. Trials were conducted between 1975 and 1991. No trials involved comparison with newer anti‐emetic drugs such as ondansetron. Comparison with placebo People had more chance of reporting complete absence of vomiting (3 trials; 168 participants; RR 5.7; 95% CI 2.6 to 12.6; low quality evidence) and complete absence of nausea and vomiting (3 trials; 288 participants; RR 2.9; 95% CI 1.8 to 4.7; moderate quality evidence) when they received cannabinoids compared with placebo. The percentage of variability in effect estimates that was due to heterogeneity rather than chance was not important (I2 = 0% in both analyses). People had more chance of withdrawing due to an adverse event (2 trials; 276 p