A systematic review and meta-analysis of pregabalin preclinical studies

Despite large efforts to test analgesics in animal models, only a handful of new pain drugs have shown efficacy in patients. Here, we report a systematic review and meta-analysis of preclinical studies of the commercially successful drug pregabalin. Our primary objective was to describe design characteristics and outcomes of studies testing the efficacy of pregabalin in behavioral models of pain. Secondarily, we examined the relationship between design characteristics and effect sizes. We queried MEDLINE, Embase, and BIOSIS to identify all animal studies testing the efficacy of pregabalin published before January 2018 and recorded experimental design elements addressing threats to validity and all necessary data for calculating effect sizes, expressed as the percentage of maximum possible effect. We identified 204 studies (531 experiments) assessing the efficacy of pregabalin in behavioral models of pain. The analgesic effect of pregabalin was consistently robust across every etiology/measure tested, even for pain conditions that have not responded to pregabalin in patients. Experiments did not generally report using design elements aimed at reducing threats to validity, and analgesic activity was typically tested in a small number of model systems. However, we were unable to show any clear relationships between preclinical design characteristics and effect sizes. Our findings suggest opportunities for improving the design and reporting of preclinical studies in pain. They also suggest that factors other than those explored in this study may be more important for explaining the discordance between outcomes in animal models of pain and those in clinical trials.