Clozapine/Anticholinergics 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:

These medicines can each slow down or stop movement in the intestines. Taking them together can increase the risk of side effects.

What might happen:

Constipation may start or get worse with the combination. Rarely, serious complications may occur, including complete bowel blockage and death.

What you should do about this interaction:

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 (e.g. doctor or pharmacist) may already be aware of this 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: 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.

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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.