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FDA strengthens warning that untreated constipation caused by schizophrenia medicine clozapine (Clozaril) can lead to serious bowel problems

FDA Drug Safety Podcast


Welcome to the FDA Drug Safety Podcast for health care professionals from the Division of Drug Information. This is Lesley Navin, Advanced Practice Nurse.

On January 28, 2020, FDA strengthened an existing warning that constipation caused by the schizophrenia medicine clozapine (brand names Clozaril, Fazaclo ODT, and Versacloz) can progress to serious bowel complications. This can lead to hospitalization or even death if constipation is not diagnosed and treated quickly. Constipation is a frequent and known side effect of clozapine, but serious and fatal events continue to be reported.

Clozapine affects bowel function in a majority of patients producing effects ranging from constipation, a common occurrence, to serious but uncommon bowel problems, including complete blockage of the bowel. We found that because of the way clozapine works this risk is greater with clozapine than with the other schizophrenia medicines in its drug class. The risk is further increased at higher doses of clozapine and when co-prescribed with anticholinergics and other medicines that cause constipation, including opioids.

We are requiring a new warning and updates about this risk be added to the prescribing information of all clozapine products. Clozapine is used to treat schizophrenia in patients whose symptoms are not controlled with standard treatment. It is effective in reducing the risk of suicidal thinking and self-harm in patients with schizophrenia or schizoaffective disorder.

Health care professionals should evaluate bowel function before starting patients on clozapine and avoid co-prescribing clozapine with anticholinergics. Advise patients of the significant risk of constipation and life-threatening bowel issues and the need to stay hydrated to prevent constipation.

Advise patients to contact a health care professional right away if they have difficulty passing stool, do not have a bowel movement at least three times a week or less than their normal frequency, or are unable to pass gas. Consider prophylactic laxative treatment when starting clozapine in high-risk patients.

We reviewed the period from 2006 to 2016 and identified 10 cases describing constipation that progressed to serious bowel problems resulting in hospitalization, surgery, or death. This number includes only cases submitted to FDA or found in the medical literature, so there may be additional cases about which we are unaware.

Side effects involving clozapine should be reported to FDA’s MedWatch program at www.fda.gov/medwatch.

A link to the full communication detailing specific information for health care professionals and the complete Data Summary can be found at www.fda.gov/DrugSafetyCommunications. If you have drug questions, you can reach us at druginfo@fda.hhs.gov.

And follow us on Twitter @FDA_Drug_Info. Thanks for listening.

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