Multiple inductive effects of carbamazepine on combined therapy with paliperidone and amlodipine.

ABSTRACT

WHAT IS KNOWN AND OBJECTIVE: Carbamazepine is a potent inducer of cytochrome P450 3A and P-glycoprotein. However, there are no reports of the effects of carbamazepine on more than one co-administered drug. CASE SUMMARY: A 53-year-old female patient with schizophrenia and hypertension was on paliperidone 12 mg/day and amlodipine 5 mg/day. When carbamazepine was added to this prescription, the plasma concentrations of both drugs decreased dramatically in a dose-dependent manner. Although the patient's psychotic symptoms did not change, as a result, her mean blood pressure increased to 160·1/103·6 mmHg from 138·4/91·4 mmHg at a carbamazepine dose of 600 mg/day. WHAT IS NEW AND CONCLUSION: Theses cases show the effect of carbamazepine induction on two drugs simultaneously. Care is required when carbamazepine is added to drug regimens including paliperidone or amlodipine alone or together.