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Use of the self-controlled case series method in drug safety assessment

The randomized double-blind controlled clinical trial (RCT) is the undisputed gold-standard for assessing drug efficacy. However the RCT is usually insufficiently powered, or too brief, to detect rare but serious adverse effects or modest but important increases in the risk of common disease outcomes (such as coronary heart disease events) that can have a major population impact in absolute terms. Pooling individual trials via meta-analyses sometimes helps but the reporting of information on adverse effects in clinical trials is often incomplete or poorly quantified, particularly when compared to the efficacy endpoints. Clinically significant and unexpected abnormal laboratory values may not be detected as not all are routinely included in trial protocols. Most RCTs also tend to exclude the elderly, patients with co-morbidity or pregnancy, and this reduces the generalisability of these data. Therefore, at the time of product launch, there are often limited safety data of any new drug, in both the short- and longer-term which is directly applicable to that of the target population. Drugs in use therefore need to remain under constant surveillance (pharmacovigilance) and study by observation (pharmacoepidemiology) Pharmacovigilance systems identify safety signals (signal detection) and thus serve to generate hypothesis. Pharmacoepidemiology tests such hypothesis (signal validation) and quantifies the risk. Both pharmacovigilance and pharmacoepidemiology have limitations, are complementary and only partially overlap.