During the NVKFB (Dutch Society for Clinical Pharmacology & Biopharmacy) & NVF (Dutch Pharmacological Society) Spring Day 2025 in The Netherlands, Laura Nijboer presented a poster on the Metamizole DDI Manager.

Metamizole (dipyrone) is a widely used NSAID with analgesic, antipyretic, and spasmolytic properties. In the Netherlands, it is commonly used intramurally for the management of postoperative pain for durations of less than 24 hours. However, it is increasingly prescribed for longer periods as an alternative to other NSAIDs.

In countries such as Germany and Switzerland, metamizole is a preferred NSAID both intra- and extramurally. Despite decades on the market, limited information is available on metamizole’s interaction potential.

In addition to the rare adverse effect of agranulocytosis, metamizole can interfere with several cytochrome P450 (CYP) enzymes, including CYP3A4. To assess the DDI potential, metamizole was reviewed with 983 comedications for potential DDI interactions. The results classified 59.9% (589) as “no or minimal clinically relevant interaction; no action needed” (green), 21.8% (214) as “clinically relevant interaction expected; action needed” (orange) and 18.3% (180) “severe interaction expected, do not co-administer” (red).

Metamizole use up to 24 hours is not considered clinically relevant, as CYP induction does not reach its maximum effecter within this timeframe. For long-term use, all identified DDI pairs have been incorporated into the Metamizole DDI Manager, an online tool designed to guide clinicians in managing interaction with metamizole and relevant comedications.