Adverse reactions to over-the-counter analgesics: an epidemiological evaluation.

Over-the-counter (OTC) analgesics, i.e. aspirin, paracetamol, and dipyrone, continue to be the most widely used drug group. Recently, some non-steroidal anti-inflammatory drugs became available as OTC drugs. Our concern has persisted during the past decade in view of the following adverse effects: hepatotoxicity (including the drug aetiology of Reye's Syndrome), analgesic nephropathy, blood dyscrasias, gastrointestinal complications, and certain hypersensitivity reactions. Of particular interest are the identification of high risk groups and questions relating to geographical risk variations. Although the above adverse reactions are thought to be rare, the massive use of OTC analgesics requires quantitative estimates of the risk involved. What is needed is not only the relative risk, but an estimate of the excess risk of reactions in users. This is the parameter to be used in comparative evaluation of the public health hazard and the resulting regulatory action. Such data are generally lacking. A recent international population-based case-control study on the drug aetiology of agranulocytosis and aplastic anaemia is a rare example of such research. Unfortunately, on occasion the experience with that study has been that the provision of reassuring quantitative data is not a guarantee for scientifically based decisions in the face of heated pharmaco-political debates. Still, because government bodies do not foster the needed research, it remains for the pharmaceutical industry to assume the responsibility for continued pharmacoepidemiological assessment of the safety of OTC analgesics.