[Detection and evaluation of adverse drug effects]

Adverse drug reactions (ADRs) occur in about 5% of drug-treated patients. Hospital admissions are caused by ADRs in 5% of patients and roughly 2% of hospitalized patients will experience an ADR. The economic burden of ADRs can only be estimated. Type A reactions can be explained by the pharmacological action of the drugs, and are preventable in many cases. However, Type B reactions involving the immune system and/or idiosyncratic reactions occur rarely and most of them are not fully understood. Genotyping represents an elegant method to explain the presence of abnormal enzyme activities and allows prediction of adverse drug effects in individual cases. Typical time frames have been identified for the occurrence of hypersensitivity reactions, although definite causality assessment is often impeded due to the absence or unavailability of specific laboratory tests and the impossibility of rechallenge. Diagnosis of an ADR is often difficult due to comorbidity and polypharmacy, thus causality assessment is often divergent even between specialists. In Germany, ADRs are reported preferably to the manufacturer of the suspicious drug and then collected and evaluated at the Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM. However, total number and quality of reported ADRs could be improved.