Fluvoxamine-methadone interaction

Objective: The aim of this paper is to report a case of symptomatic methado ne toxicity associated with fluvoxamine treatment. Clinical picture: A 28-year-old woman was admitted to hospital with severe hypoxaemia and hypercapnia indicating hypoventilation. Medication prior to admission had been stable and included methadone 70 mg daily and diazepam 2 mg twice daily. Three weeks before admission she had commenced treatment w ith fluvoxamine. Treatment: Methadone was decreased to 50 mg daily and diazepam was tapered to zero. Outcome: The serum methadone concentration decreased and oxygenati on improved considerably. Conclusions: Clinicians should be aware of the potential for a significant drug interaction between fluvoxamine and methadone.