[FDA Drug Safety Communication, January 28, 2020] – The U.S. FDA strengthens warning that constipation caused by clozapine can, uncommonly, progress to serious bowel complications. This can lead to hospitalization or even death if constipation is not diagnosed and treated quickly.
Clozapine affects how the intestines function in the majority of patients. It produces effects ranging from constipation, which is a common occurrence, to serious but uncommon bowel problems, including complete blockage of the bowel.
FDA recommends that health care professionals should:
- Evaluate bowel function before starting a patient on clozapine.
- Avoid co-prescribing clozapine with other anticholinergic medicines that can cause gastrointestinal hypomotility.
- Advise patients frequently of the significant risk of constipation and life-threatening bowel issues and the need to stay hydrated to prevent constipation.
- Question patients about the frequency and quality of their bowel movements throughout treatment.
- Advise patients to contact a health care professional right away if they have difficulty having a bowel movement or passing stools, do not have a bowel movement at least three times a week or less than their normal frequency, or are unable to pass gas.
- Monitor patients for symptoms of potential complications associated with gastrointestinal hypomotility such as nausea, abdominal distension or pain, and vomiting.
- Consider prophylactic laxative treatment when starting clozapine in patients with a history of constipation or bowel obstruction.
Source: FDA Drug Safety Communication, January 28, 2020
FDA BOXED WARNINGS
1. Severe Neutropenia or Agranulocytosis
Clozapine can cause severe neutropenia, which can lead to serious and fatal infections. Its use should be limited to patients:
- with schizophrenia who are non-responsive to, or intolerant of, classical antipsychotic agents, or with schizophrenia or schizoaffective disorder who are at risk of recurrent suicidal behaviour,
- who have initially normal leukocyte findings (white blood cell count (WBC) ≥3500/mm³ (3.5 x 109/L), and absolute neutrophil counts (ANC) ≥2000/mm³ (2.0 x 109/L)),
- and in whom regular white blood cell counts and absolute neutrophil counts can be performed as follows: weekly during the first 18 weeks of therapy, and at least every 4 weeks thereafter throughout treatment. Monitoring must continue throughout treatment and for 4 weeks after complete discontinuation of Clozapine.
Patients must be advised to immediately report symptoms consistent with severe neutropenia or infection (e.g., fever, weakness, lethargy, or sore throat).
2. Increased mortality in elderly patients with dementia-related psychosis
Elderly patients with dementia-related psychosis treated with antipsychotic drugs are at an increased risk of death. Clozapine is not approved for this condition.
3. Orthostatic hypotension, bradycardia, syncope
Clozapine has alpha-blocking activity and can cause orthostatic hypotension, with or without syncope. Rarely, collapse can be profound and may be accompanied by cardiac and/or respiratory arrest. The risk is dose-related and highest during the initial titration period, particularly with rapid dose escalation. These reactions can occur with the first dose, with doses as low as 12.5 mg per day. Initiate treatment at 12.5 mg once or twice daily; titrate slowly; and use divided dosages. Use Clozapine cautiously in patients with cardiovascular or cerebrovascular disease or conditions predisposing to hypotension (e.g., dehydration, use of antihypertensive medications).
4. Seizures
Clozapine may lower seizure threshold. The risk is dose-related. Initiate treatment at 12.5 mg, titrate gradually, and use divided dosing. Use caution when administering Clozapine to patients with a history of seizures or other predisposing risk factors for seizure (CNS pathology, medications that lower the seizure threshold, alcohol abuse). Caution patients about engaging in any activity where sudden loss of consciousness could cause serious risk to themselves or others.
5. Myocarditis, cardiomyopathy and mitral valve incompetence
Fatal myocarditis and cardiomyopathy have occurred with Clozapine treatment. Discontinue Clozapine and obtain cardiac evaluation if findings suggest these cardiac reactions. Tachycardia that persists at rest, accompanied by arrhythmias, shortness of breath or signs and symptoms of heart failure, may rarely occur during the first month of treatment and very rarely thereafter. The occurrence of these signs and symptoms necessitates an urgent diagnostic evaluation for myocarditis, especially during the titration period. Consider the possibility of myocarditis in patients receiving Clozapine who present with unexplained fatigue, dyspnoea, tachypnoea, fever, chest pain, tachycardia, palpitations, other signs and symptoms of heart failure, ECG changes (such as ST-T wave abnormalities) or arrhythmias.
Generally, patients with Clozapine-related myocarditis or cardiomyopathy should not be rechallenged with Clozapine
Source: CLOZARIL® Product Monograph