Epidemiological assessment of drug-induced disease

Adverse reactions are a potential concern for physicians when they prescrib e or recommend drugs. Epidemiological principles, when combined with clinic al judgment, can be of help in this situation, starting with an appreciatio n of the strengths and weaknesses of different sources of information on ad verse reactions-clinical trials, case reports, and formal epidemiological s tudies. The latter studies generally provide the most comprehensive informa tion on the risks of serious adverse drug reactions. An understanding of th e different types of risk estimates, relative and absolute, is also needed- we stress the value of the absolute risk as the best measure of the impact of an adverse reaction. Rare serious reactions, although striking, have lit tle impact on individual risk, whereas more common reactions, even with muc h lower fatality rates, are more likely to lead to adverse outcomes for pat ients. The importance of balancing risks and benefits, taking into account all the information about an individual patient's risk profile, is also hig hlighted.