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Fluvoxamine augmentation increases serum mirtazapine concentrations three- to fourfold
A K Anttila1, L Rasanen, E V Leinonen
1Department of Psychiatry, Tampere University Hospital, Pitkäniemi, Finland. samia@koti.tpo.fi
The Annals of Pharmacotherapy
|October 26, 2001
Summary
Fluvoxamine significantly increases mirtazapine levels, potentially causing adverse effects or mood changes. This drug interaction may require mirtazapine dosage adjustments for patient safety.
Area of Science:
- Pharmacology
- Clinical Pharmacy
Background:
- Mirtazapine is metabolized by cytochrome P450 isoenzymes CYP1A2, CYP2D6, and CYP3A4.
- Fluvoxamine is known to inhibit these isoenzymes.
Observation:
- A 17-year-old male experienced a threefold increase in mirtazapine concentration with added fluvoxamine, accompanied by increased anxiety.
- A 43-year-old female showed a fourfold increase in mirtazapine concentration with added fluvoxamine, alongside mood improvement.
Findings:
- This report details the first observed interaction between fluvoxamine and mirtazapine.
- Fluvoxamine likely causes clinically significant inhibition of mirtazapine metabolism.
Implications:
- Concurrent use of fluvoxamine and mirtazapine can lead to substantial increases in mirtazapine plasma concentrations.
- Clinicians should monitor patients for potential toxicity or altered therapeutic effects and consider mirtazapine dose adjustments when initiating or discontinuing fluvoxamine.