Pharmacogenetics deals with the differences in effect of drugs caused by genetic variation. Differences can occur in therapeutic effect and in adverse events. Genetic variation in metabolism may result in high concentrations of drugs and an increased risk of adverse effects in slow metabolizers, which is important when using for example antidepressants or chemotherapy. Genetic variation also occurs in proteins interacting with drugs, which may change the effect of e.g. asthma drugs and antipsychotics. The selection of drugs and their dosages may be improved, and the number of adverse effects reduced by pharmacogenetic investigations. However, it may be important also in case of medical examinations for insurances and job appointments, since some patients may turn out to need expensive drugs or to be susceptible to a certain disease. Therefore, the use of genetic data in these instances has to be regulated.