Omeprazole reduces clozapine plasma concentrations. A case report

Area of Science:

• Pharmacology
• Psychiatry

Background:

• Clozapine, an atypical antipsychotic, undergoes metabolism primarily via cytochrome P450 isoenzyme 1A2 (CYP1A2).
• Drug interactions involving clozapine are common and can significantly impact its therapeutic efficacy and safety profile.

Observation:

• Two patients with schizoaffective disorder experienced reduced clozapine plasma levels after initiating omeprazole for gastrointestinal issues.
• The reduction in clozapine concentrations was approximately 41.9% and 44.7% in the two patients.

Findings:

• Omeprazole, a proton pump inhibitor, is known to induce CYP1A2 activity.
• The observed decrease in clozapine levels suggests omeprazole-induced CYP1A2 induction, accelerating clozapine metabolism.

Implications:

• Close monitoring of clozapine plasma levels is crucial when co-administered with omeprazole.
• Dosage adjustments for clozapine may be required, or alternative treatments to omeprazole should be considered to maintain therapeutic efficacy.