Clozapine. Malignant constipation can kill

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Clozapine. Malignant constipation can kill

Clozapine is used for treatment-resistant schizophrenia. Agranulocytosis and neutropenia are the usual concerns but there are more deaths from ileus/megacolon. The most common reported signs and symptoms of severe constipation are moderate to severe abdominal pain, abdominal distension, vomiting, paradoxical overflow diarrhea, reduced appetite and nausea.1

 A good pre-treatment baseline for bowel movements helps and advice on diet, exercise and fluid intake is needed. The Auckland DHB guidelines indicate concern when Clozapine patients have not had a bowel movement for two or more days.

 A low threshold for prescribing laxatives such as senna with docusate or a macrogol laxative is reasonable. Avoid medications that can cause constipation such as opiates or those with anti-cholinergic effects.2  

Risk situations include dose increases, the first four months of treatment, smoking cessation, as well as interactions with medications such as the macrolides and SSRIs. For the bone marrow issues regular leukocyte and differential blood counts are needed.2 


  1. Clozapine ­ Close Monitoring Required. Medsafe (2015) Click here
  2. Safer prescribing of high-risk medicines: Clozapine BPAC (2014) Click here 

    Gems are chosen by the Goodfellow director Dr. Bruce Arroll to be either practice changing or practice maintaining. The information is educational and not clinical advice.

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    As published in NZ Doctor 19/07/2017