Clozapine/Anticholinergics that Prolong QT 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:

Clozapine can affect your heart's rhythm and slow down or stop movement in the intestines. Other drugs can have the same effects.

What might happen:

Taking clozapine with other agents that can affect your heart rhythm may increase your risk of irregular heartbeat, which may be life-threatening.In addition, the combination of clozapine with your other medicine 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:

Make sure your healthcare professionals (e.g. doctor or pharmacist) know that you are taking these medicines together and all other medicines you are taking. Your doctor may want to perform an electrocardiogram (ECG) on you to check your heart rate and rhythm. Let your doctor know right away if you notice any irregular heartbeat or have any dizziness or fainting episodes.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.

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  • 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.
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  • 7.Drew BJ, Ackerman MJ, Funk M, Gibler WB, Kligfield P, Menon V, Philippides GJ, Roden DM, Zareba W. Prevention of torsade de pointes in hospital settings: a scientific statement from the American Heart Association and the American College of Cardiology Foundation. J Am Coll Cardiol 2010 Mar 2;55(9):934-47.
  • 8.Woosley RL, Romero KA. www.Crediblemeds.org, QTdrugs List, AZCERT, Inc. 1822 Innovation Park Dr., Oro Valley, AZ 85755. November 17, 2015.

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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.