clozapine; Clozaril, Fazacio ODT (cont.)

The most common side effect of clozapine is drowsiness. Other side effects include increased heart rate, increased salivation, headache, tremor, low blood pressure, and fever. Clozapine has anticholinergic effects that interfere with the function of smooth muscles. This can lead to blurred vision and difficulty urinating (when there is enlargement of the prostate) due to effects on the muscles of the eye and bladder. Clozapine slows the intestine and leads to constipation in approximately 14% of patients. Paralysis of the intestinal muscles can lead to paralytic ileus, a condition in which the intestine stops working.

Clozapine also may cause extrapyramidal effects (sudden, often jerky, involuntary motions of the head, neck, arms, body, or eyes). Like other anti-psychotics, clozapine also may cause tardive dyskinesia (potentially irreversible involuntary movements). The risk of such reactions appears to be lower with clozapine than with older anti-psychotics, perhaps due to its weaker effects on dopamine type 2 receptors.

Although there is no clear link between clozapine and diabetes, patients should be tested during treatment for elevated blood-sugars. Additionally, persons with risk factors for diabetes, including obesity or a family history of diabetes, should have their fasting levels of blood sugar tested before starting treatment and periodically throughout treatment to detect the onset of diabetes. Any patient developing symptoms that suggest diabetes during treatment should be tested for diabetes.

Clozapine is eliminated from the body by enzymes (P450) in the liver. Numerous medications can increase or decrease the activities of these enzymes leading to low (potentially ineffective) or high (potentially toxic) levels of clozapine in the blood. When used with these medications, the dose of clozapine may need to be reduced or increased.

Reference: FDA Prescribing Information


Last Editorial Review: 12/22/2010



Report Problems to the Food and Drug Administration

You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

Pill Finder Tool

Need help identifying pills and medications?
Use the pill identifier tool on RxList.


Back to Medications Index