Abstract
BACKGROUND: Metamizole is the most commonly prescribed analgesic drug in Germany, with 280 million daily doses prescribed per year. It is generally considered safe, yet it is controversial and not approved for use in many countries because of the very rare, but potentially lethal risk of agranulocytosis. METHODS: This narrative review is based on pertinent publications retrieved by a search in PubMed and other databases on the topics of metamizole/dipyrone, its adverse effects (especially agranulocytosis), mechanisms of action, and its interactions with other drugs. RESULTS: There are some 44 reported cases of agranulocytosis in Germany per year. Predicting the individual risk on the basis of genetic factors is not currently possible. Registry studies and data from pharmacovigilance databases yield country-specific incidences of agranulocytosis (per quantity of drug prescribed) that vary from 0.65 to 1400 per million in countries across Europe. In addition to pharmacovigilance data, this article also provides an overview of mechanisms of action, additional adverse effects, and the drug interactions of metamizole, e.g., the induction of CYP3A4. CONCLUSION: Metamizole is a powerful analgesic drug whose varying regulatory status from country to country reflects its mixed benefit-risk profile. Patients must be instructed about the risk of agranulocytosis and the symptoms by which it can be recognized early.