Clozapine/Carbamazepine Interactions

This information is generalized and not intended as specific medical advice. Consult your healthcare professional before taking or discontinuing any drug or commencing any course of treatment.

Medical warning:

Serious. These medicines may interact and cause very harmful effects. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.

How the interaction occurs:

When clozapine and carbamazepine are taken together, your body may process clozapine more quickly.In addition, the combination may slow down or stop movement in the intestines.

What might happen:

The amount of clozapine in your blood may decrease and it may not work as well.In addition, taking clozapine with carbamazepine may cause or worsen constipation associated with clozapine. Rarely, serious complications may occur, including complete bowel blockage and death.

What you should do about this interaction:

Contact your healthcare professionals (e.g. doctor or pharmacist) as soon as possible about taking these two medicines together. Your provider may need to check the level of clozapine in your blood and adjust your clozapine dose to make sure it continues to work for you.Contact your doctor if you experience increased constipation or have less than three bowel movements in a week, dry, hard stools or difficulty passing gas. Let your doctor know right away if you have nausea, vomiting, bloating, or belly pain. It may be necessary to discontinue or adjust the dose of one or both medicines.To prevent constipation, you should eat more fruits, vegetables, and grains that are high in fiber; drink plenty of water and other liquids; and get enough exercise. Your healthcare professionals may already be aware of the drug interaction and may be monitoring you for it. Do not start, stop, or change the dosage of any medicine before checking with them first.

  • 1.Clozaril (clozapine tablets) US prescribing information. Novartis Pharmaceuticals Corporation April, 2020.
  • 2.USFood and Drug Administration. FDA Drug Safety Communication: FDA strengthens warning that untreated constipation caused by schizophrenia medicine clozapine (Clozaril) can lead to serious bowel problems. Available at: https://www.fda.gov/drugs/drug-safety-and-availability/fda-strengthens-war ning-untreated-constipation-caused-schizophrenia-medicine-clozapine-clozar il-can February 18, 2020.
  • 3.Peyriere H, Roux C, Ferard C, Deleau N, Kreft-Jais C, Hillaire-Buys D, Boulenger JP, Blayac JP. Antipsychotics-induced ischaemic colitis and gastrointestinal necrosis: a review of the French pharmacovigilance database. Pharmacoepidemiol Drug Saf 2009 Oct;18(10):948-55.
  • 4.Hibbard KR, Propst A, Frank DE, Wyse J. Fatalities associated with clozapine-related constipation and bowel obstruction: a literature review and two case reports. Psychosomatics 2009 Jul-Aug;50(4):416-9.
  • 5.Nielsen J, Meyer JM. Risk factors for ileus in patients with schizophrenia. Schizophr Bull 2012 May;38(3):592-8.
  • 6.Chen HK, Hsieh CJ. Risk of gastrointestinal Hypomotility in schizophrenia and schizoaffective disorder treated with antipsychotics: A retrospective cohort study. Schizophr Res 2018 May;195:237-244.
  • 7.Gerson SL, Lieberman JA, Friedenberg WR, Lee D, Marx JJ Jr, Meltzer H. Polypharmacy in fatal clozapine-associated agranulocytosis. Lancet 1991 Jul 27;338(8761):262-3.
  • 8.FDA (US Food and Drug Administration). Clozapine: Drug Safety Communication - FDA Modifies Monitoring for Neutropenia; Approves New Shared REMS Program. accessed at: http://www.fda.gov/drugs/drugsafety/ucm461853.htm September 15, 2015.
  • 9.Muller T, Becker T, Fritze J. Neuroleptic malignant syndrome after clozapine plus carbamazepine. Lancet 1988 Dec 24-31;2(8626-8627):1500.
  • 10.Raitasuo V, Lehtovaara R, Huttunen MO. Carbamazepine and plasma levels of clozapine. Am J Psychiatry 1993 Jan;150(1):169.
  • 11.Raitasuo V, Lehtovaara R, Huttunen MO. Effect of switching carbamazepine to oxcarbazepine on the plasma levels of neuroleptics. A case report. Psychopharmacology (Berl) 1994 Sep;116(1):115-6.
  • 12.Jerling M, Lindstrom L, Bondesson U, Bertilsson L. Fluvoxamine inhibition and carbamazepine induction of the metabolism of clozapine: evidence from a therapeutic drug monitoring service. Ther Drug Monit 1994 Aug; 16(4):368-74.

Selected from data included with permission and copyrighted by First Databank, Inc. This copyrighted material has been downloaded from a licensed data provider and is not for distribution, except as may be authorized by the applicable terms of use.

CONDITIONS OF USE: The information in this database is intended to supplement, not substitute for, the expertise and judgment of healthcare professionals. The information is not intended to cover all possible uses, directions, precautions, drug interactions or adverse effects, nor should it be construed to indicate that use of a particular drug is safe, appropriate or effective for you or anyone else. A healthcare professional should be consulted before taking any drug, changing any diet or commencing or discontinuing any course of treatment.