current opportunities and challenges

Pharmacoepidemiology is defined as the the study of the use and the effects of drugs in large groups of people. It can be viewed as an epidemiological discipline with particular focus on drugs. The Scandinavians pioneered the developement of methods to study drug utilization. The ATC and DDD methodology is now a widely accepted consensus on how to categorise drugs and compare sales of drugs of different potency. The hierachy of available designs to study drug effects is described. There is an inverse relationship between the validity of a study design and its resource requirements. One of the most pervasive methodological problems of pharmacoepidemiology is the possibility of confounding by indication. Often, such confounding can only be handled by mounting a randomised trial. If a trial is unethical or unfeasible, the research question has the potential of becoming af standing controversy. The emergence of large population based prescription data-bases is an exciting new development in pharmacoepidemiology. The validity of drug exposure data is dis-cussed. It is established that data from a pharmacy based database should be preferred over data from a GP based database. Whether interview data are preferable to dispensing data can not be established in general but may occasionally be inferred from the context of the research question