[Serious drug interaction between clozapine-Leponex and fluvoxamine-Fevarin]

A 67 year-old woman in steady-state treatment with clozapine 150 mg/24 h was co-medicated with 100 mg/24 h of fluvoxamine. During the next months the patient suffered from nausea and occasionally vomited, but these symptoms were ascribed to fluvoxamine, and as she mentally improved, both treatments were continued. Two months after the start of fluvoxamine her serum clozapine concentration was 7570 nmol/l or 7.5 fold higher than before fluvoxamine was added. The woman was admitted to hospital, suffering from abdominal pain, dehydration and fever (38.5 degrees C). Serum creatinine concentration was increased, but normalized during hydration. After 18 days care the woman felt well and was discharged from hospital. The case report shows that certain combinations of selective serotonin reuptake inhibitors and neuroleptic drugs should either be avoided or the serum concentrations of the drugs closely followed.