Klin Farmakol Farm. 2025;39(4):213-217 | DOI: 10.36290/far.2025.071
Induction of CYP3A4 by metamizole confirmed by TDM: a case study with quetiapine
- Oddělení klinické farmacie, Psychiatrická nemocnice Bohnice, Praha
- Katedra sociální a klinické farmacie, Farmaceutická fakulta Univerzity Karlovy v Hradci Králové
Metamizole is an analgesic and antipyretic with a long history of clinical use, although some of its pharmacological properties, including its safety profile, remain incompletely understood. Recent studies indicate that metamizole is a moderate inducer of cytochrome P450 enzymes (CYP), particularly CYP3A4 and CYP2B6, which may result in altered plasma concentrations of concurrently administered drugs that are substrates of these enzymes. This article presents a case report of a patient whose regular administration of metamizole led to a marked decrease (approximately 75%) in quetiapine plasma concentration, consistent with the moderate induction of CYP3A4. After discontinuing metamizole, quetiapine levels returned to the therapeutic range. The significance of this decline was confirmed by therapeutic drug monitoring (TDM), which enabled an accurate interpretation of this drug interaction. This case report, alongside a theoretical discussion on the inductive effects of metamizole, underscores the clinical relevance of its interaction potential and highlights the need for increased caution when co-administering it with drugs metabolised by CYP3A4 and CYP2B6.
Keywords: metamizole, quetiapine, drug interaction, CYP3A4 induction, therapeutic drug monitoring.
Received: September 22, 2025; Revised: December 7, 2025; Accepted: December 10, 2025; Published: December 22, 2025 Show citation
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