2014 Volume 5 Pages 18-22
The patient was a 67-year-old man. After the patient received a diagnosis of schizophrenia, various antipsychotics were prescribed but did not improve symptoms. However, 18 mg/day aripiprazole (APZ) was found to be highly effective and enabled the patient to continue treatment on an outpatient basis. Two weeks after prescribing clarithromycin for fever and cough, he was readmitted to our psychiatric ward because of anuresis and deterioration of bradykinesia and salivation. Biochemical analysis revealed elevated serum creatine phosphokinase (26060 U/I) and creatinine (2.2 mg/dL). On admission, the patient had a high blood concentration of APZ and its metabolite(s). APZ was therefore discontinued, but the concentration remained elevated until day 8. Hemodialysis was started on day 4 to treat persistent renal dysfunction. The patient's CYP2D6 genotype was CYP2D6*10/CYP2D6*10. The elevated APZ levels may have resulted from the inhibitory action of clarithromycin on CYP3A4 combined with the lower inherent CYP2D6 enzymatic activity of the CYP2D6*10/CYP2D6*10 genotype.