RESUMO
BACKGROUND: The Pharmaceutical industry sponsorship, research outcome and quality has been already evaluated for clinical trials in order to analyze if this kind of sponsorship affects the results of clinical trials. In this sense, this study has the aim to investigate whether placebo use allows positive outcomes regarding efficacy and safety compared to synthetic medicines. METHODS: We designed and registered a study protocol for a systematic review for methodology data. We will only randomized clinical trials that use placebo as comparator. The main outcome will be the evaluation of placebo use regarding the tendency for positive results (efficacy and security) when comparing to synthetic medicines. PubMed, Cochrane, LILACS (BVS), Web of Science, Scopus, and Excerpta Medica dataBASE (EMBASE) databases will be searched. Gray literature will be identified through the databases Proquest (Dissertation and Theses), OpenGrey and Google Scholar. Two review authors will independently assess trial quality and will extract data in accordance with standard Cochrane methodology. If necessary, we will also contact authors for additional information. The Cochrane Collaboration's risk of bias tool will be used. If feasible, it means homogenous data, we will conduct random effects meta-analysis. Subgroup analyses will be conducted for different justifications for placebo use and for studies sponsored/not sponsored by the pharmaceutical industry. RESULTS: Our present findings will indicate the effects of placebo use as comparator regarding efficacy and safety of the oral synthetic medicines. DISCUSSION: This systematic review will identify, summarize, and analyze if there is a trend for positive efficacy and safety results for synthetic medicines in clinical trials when compared with placebo and if the justification for placebo use is considered ethically acceptable. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42018110829.