Pharmacoepidemiology studies the use of drugs and their effects in large numbers of people after market authorization.  It overcomes limitations from premarketing randomised clinical drug trials (RCTs), which are not representative of patients in real life clinical care, and which do not allow studying rare (with frequencies ≥0.1%) or long-term severe side effects. Typical pharmaco-epidemiological studies use advanced epidemiological methods to study large electronic healthcare databases (EHDs) with medical records of millions of patients for effectiveness and safety of drugs. Regulatory authorities such as the US Food and Drug Administration (FDA) or the European Medicines Agency (EMA) assess the risk/benefit balance of medicines to decide whether their market authorisation may be restricted or completely withdrawn. Regulatory review is supported by evidence from clinical trials and pharmacoepidemiological studies that are either published, conducted voluntary or upon the regulator´s request by manufacturers of medicines (post-authorisation safety studies [PASS]). A PASS is defined in EU Directive 2001/83/EC. PASS studies will then be assessed by the EMA’s Pharmacovigilance Risk Assessment Committee , which recommends on the maintenance of the terms of the marketing authorization. This is then forwarded to the Committee for Medicinal Products for Human Use for final decision making.