40 year old patient with history of schizophrenia stabilized on clozapine presented with recent worsening of psychotic symptoms. He recently started smoking and initiated treatment for GERD. Which drug-drug interaction is responsible this presentation?
Literature review done by Singh et al compared the list of medications interacting with clozapine and how this affect serum level changes in clozapine. The following table will summarize these findings:-
|Medications||Serum Clozapine Level||CYP450|
|Fluvoxamine||Increase in Clozapine level||1A2; 3A4|
|Paroxetine||Increase in Clozapine level||2D6|
|Sertraline||Increase in Clozapine level||1A2|
|Carbamazepine||Decrease in Clozapine level||Pan-Inducer|
|Valproic Acid||Mixed Reports||1A2|
|Aripiprazole||Decrease in Clozapine level||Not known|
|Ciprofloxacin||Increase in Clozapine level||1A2; 3A4|
|Erythromycin||Increase in Clozapine level||3A4|
|Isoniazid||Increase in Clozapine level||1A2|
|Rifampin||Decrease in Clozapine level||1A2; 3A4|
|PROTON PUMP INHIBITORS|
|Omeprazole||Decrease in Clozapine level||1A2; 3A4|
|Ethinylestradiol||Increase in Clozapine level||1A2; 2C19|
|St. John’s Wort||Decrease in Clozapine level||3A4|
|Smoking||Decrease in Clozapine level||1A2|
|Caffeine||Increase in Clozapine level||1A2|
Source: Singh, H., Dubin, W.R. and Kaur, S. (2015) ‘Drug interactions affecting clozapine levels’, Journal of Psychiatric Intensive Care, 11(1), pp. 52–65.
Please do post your questions or comments below.
Dr. Harvinder Singh, M.D. (Admin)
Enroll in our online course to have access to all important clinically relevant psychiatry topics in one place.