Note: This document contains side effect information about clozapine. Some of the dosage forms listed on this page may not apply to the brand name Clozaril.
Common side effects of Clozaril include: hypotension, fever, tachycardia, constipation, dizziness, headache, nausea, sedated state, vomiting, and weight gain. Other side effects include: syncope, and diaphoresis. See below for a comprehensive list of adverse effects.
Applies to clozapine: oral suspension, oral tablet, oral tablet disintegrating
Oral route (Suspension; Tablet; Tablet, Disintegrating)
Risks associated with the use of clozapine include severe neutropenia, orthostatic hypotension, seizures, myocarditis, cardiomyopathy, and mitral valve incompetence. Severe neutropenia can lead to serious infection and death. Monitor absolute neutrophil count (ANC) prior to and during treatment. Monitor for symptoms of severe neutropenia and infection. Clozapine is available only through a restricted program under a Risk Evaluation Mitigation Strategy (REMS) called the Clozapine REMS Program. Orthostatic hypotension, bradycardia, syncope, cardiac arrest, and seizures have occurred. The risk is dose-related. Initiate treatment at 12.5 mg, titrate gradually, and use divided dosing. Use with caution in patients with history of or risk factors for seizure. Myocarditis and cardiomyopathy have occurred and can be fatal. Discontinue and obtain cardiac evaluation if findings suggest these cardiac reactions. Elderly patients with dementia-related psychosis treated with atypical antipsychotic drugs are at an increased risk of death. Clozapine is not approved for the treatment of patients with dementia-related psychosis.
Along with its needed effects, clozapine (the active ingredient contained in Clozaril) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur while taking clozapine:
Incidence not known
Some side effects of clozapine may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
Incidence not known
Applies to clozapine: oral suspension, oral tablet, oral tablet disintegrating
The most commonly reported side effects included salivary hypersecretion, somnolence, and weight gain.
Very common (10% or more): Salivary hypersecretion/hypersalivation (up to 48%), salivation (up to 31%), constipation (up to 25%), nausea (up to 17%), vomiting (up to 17%), dyspepsia (up to 14%)
Common (1% to 10%): Abdominal discomfort/dyspepsia/heartburn, diarrhea, dry mouth
Rare (0.01% to 0.1%): Acute pancreatitis, Dysphagia, ileus impaction, pancreatitis
Very rare (less than 0.01%): Fecal impaction/intestinal obstruction/paralytic ileus, parotid gland enlargement
Frequency not reported: Colitis, swallowing difficulty, tongue protrusion
Postmarketing reports: Intestinal infarction/ischemia/fatal intestinal infarction/ischemia, megacolon/fatal megacolon, salivary gland swelling
Very common (10% or more): Somnolence (up to 46%), drowsiness/sedation (up to 39%), dizziness (up to 27%), vertigo (up to 19%), headache (up to 10%)
Common (1% to 10%): Akathisia, akinesia, convulsions/myoclonic jerks/seizures, dysarthria, extrapyramidal symptoms, hypokinesia, syncope, tremor
Uncommon (0.1% to 1%): Neuroleptic malignant syndrome
Very rare (less than 0.01%): Tardive dyskinesia
Frequency not reported: Dystonia
Postmarketing reports: Abnormal EEG, cholinergic syndrome, clozapine-induced seizures, EEG changes, motor instability, myasthenic syndrome, myoclonus, paresthesia, pleurothotonus, possible cataplexy, post-discontinuation cholinergic rebound adverse reactions, sensory instability, status epilepticus
The cumulative incidence of seizure at 1 year is approximately 5% based on pre-marketing testing. The risk is dose-related.
Extrapyramidal symptoms that occur appear to be milder and less frequent than other antipsychotic drugs. There have been no reports of tardive dyskinesia directly attributable to clozapine; however, the syndrome has been reported in a few patients who were treated with other antipsychotics prior to receiving clozapine. A causal relationship can neither be established nor excluded.
Cholinergic syndrome occurred after abrupt withdrawal.
Diabetes mellitus occurred in patients without a history of hyperglycemia or diabetes mellitus.
Pooled data from 8 studies in patients with schizophrenia found the mean change in fasting blood glucose in clozapine (the active ingredient contained in Clozaril) treated patients was +11 mg/dL; pooled data from 10 studies revealed clozapine treatment was associated a mean increase of 13 mg/dl in total cholesterol; pooled data from 11 studies showed a weight gain of 7% or greater relative to baseline body weight occurred in 35% of patients with a mean weight gain of 3.7 kg.
Very common (10% or more): Increased weight/weight gain (up to 31%)
Common (1% to 10%): Anorexia
Rare (0.01% to 0.1%): Aggravated diabetes, diabetes mellitus, hyperosmolar coma, impaired glucose tolerance, ketoacidosis, severe hyperglycemia
Very rare (less than 0.01%): Hypercholesterolemia, hypertriglyceridemia
Frequency not reported: Pseudopheochromocytoma
Postmarketing reports: Hypernatremia, hyperuricemia, obesity, weight loss
Very common (10% or more): Tachycardia (up to 25%), hypotension (up to 13%), hypertension (up to 12%)
Common (1% to 10%): ECG changes, postural hypotension
Rare (0.01% to 0.1%): Arrhythmias, circulatory collapse, myocarditis, pericardial effusion, pericarditis, thromboembolism, ventricular arrhythmia, ventricular fibrillation, ventricular tachycardia
Very rare (less than 0.01%): Cardiac arrest, cardiomyopathy/clozapine-related cardiomyopathy, QT prolongation, skin reactions, Torsade de pointes
Frequency not reported: Angina pectoris/chest pain, myocardial infarction/fatal myocardial infarction, pigmentation disorder, venous thromboembolism
Postmarketing reports: Atrial fibrillation, deep vein thrombosis, mitral valve incompetence, palpitations
Isolated cases of cardiac arrhythmias, pericarditis/pericardial effusion, and myocarditis have been reported. Postmarketing, very rare events of ventricular tachycardia, cardiac arrest, and QT prolongation which may be associated with Torsades de pointes have been observed, although there is no conclusive causal relationship to use of this drug.
Very common (10% or more): Insomnia (up to 20%)
Common (1% to 10%): Agitation, confusion, disturbed sleep/nightmares, restlessness
Uncommon (0.1% to 1%): Dysphemia
Rare (0.01% to 0.1%): Delirium, dream activity intensification
Very rare (less than 0.01%): Obsessive compulsive disorder/symptoms
Frequency not reported: Neonatal drug withdrawal syndrome
Very common (10% or more): Fever/hyperthermia (up to 13%)
Common (1% to 10%): Benign hyperthermia, fatigue, temperature regulation disturbance
Very rare (less than 0.01%): Sudden unexplained death
Postmarketing reports: Falls, polyserositis, sepsis
Common (1% to 10%): Decreased white blood cells, eosinophilia, leukocytosis, leukopenia, neutropenia
Uncommon (0.1% to 1%): Agranulocytosis
Rare (0.01% to 0.1%): Anemia
Very rare (less than 0.01%): Thrombocythemia, thrombocytopenia
Postmarketing reports: Elevated hematocrit, elevated hemoglobin, granulocytopenia, increased erythrocyte sedimentation rate, mild leukopenia, moderate leukopenia, severe leukopenia, thrombocytosis
During pre-marketing testing, the cumulative incidence of agranulocytosis at one year was reported to be 1.3%. Based on Clozaril National Registry (US patients) data collected up to April 1995, a hematologic risk analysis found the incidence of agranulocytosis rises steeply during the first 2 months, peaks at approximately the third month, and decreases at 6 months of therapy; after 6 months, the incidence decreases further, however, it never reaches zero. Individuals with an initial episode of moderate leukopenia (WBC of at least 2000/mm3 and less than 3000/mm3) are at an increased risk of having a subsequent episode of agranulocytosis.
In the UK, agranulocytosis occurred within the first 18 weeks in approximately 70% of patients who developed the condition.
In clinical trials, eosinophil counts of greater than 700/mm3 occurred in approximately 1% of patients. Eosinophilia has been co-reported with some cases of myocarditis (approximately 14%) and pericarditis/pericardial effusion, although it is unknown whether eosinophilia is a reliable predictor of carditis.
Common (1% to 10%): Urinary abnormalities, urinary incontinence, urinary retention
Very rare (less than 0.01%): Dysmenorrhea, ejaculation change, impotence, priapism
Postmarketing reports: Nocturnal enuresis, retrograde ejaculation
Common (1% to 10%): Rash, sweating/sweating disturbance
Frequency not reported: Leukocytoclastic vasculitis
Postmarketing reports: Erythema multiforme, photosensitivity, skin pigmentation disorder, Stevens-Johnson syndrome
Common (1% to 10%): Blurred vision, visual disturbances
Postmarketing reports: Narrow angle glaucoma, periorbital edema
Common (1% to 10%): Elevated liver enzymes
Rare (0.01% to 0.1%): Cholestasis, cholestatic jaundice, hepatitis
Very rare (less than 0.01%): Fulminant hepatic necrosis
Postmarketing reports: Cholestatic injury, hepatic cirrhosis, hepatic fibrosis, hepatic injury, hepatic necrosis, hepatic steatosis, hepatotoxicity, jaundice, liver failure, liver transplant, mixed injury
Common (1% to 10%): Rigidity
Rare (0.01% to 0.1%): Creatine phosphokinase elevation
Frequency not reported: Muscle pain, muscle spasms, muscle weakness, neck muscle spasm, systemic lupus erythematosus
Postmarketing reports: Rhabdomyolysis
Aspiration of ingested food usually occurred in patients with dysphagia or in acute overdose.
Rare (0.01% to 0.1%): Aspiration of ingested food, lower respiratory tract infection/fatal lower respiratory tract infection, pneumonia, pulmonary embolism, respiratory arrest, respiratory depression, respiratory depression/arrest with/without circulatory collapse
Very rare (less than 0.01%): Allergic asthma
Frequency not reported: Difficulty breathing, nasal congestion, throat tightness
Postmarketing reports: Pleural effusion, sleep apnea/sleep apnea syndrome
Very rare (less than 0.01%): Acute interstitial nephritis/interstitial nephritis
Postmarketing reports: Renal failure
Frequency not reported: Angioedema
Postmarketing reports: hypersensitivity reactions
Postmarketing reports: Pseudopheochromocytoma
Medically reviewed by BestRx Medical Team Last updated on 1/1/2020.
Source: Drugs.com Clozaril