Clozaril (Clozapine) for Schizophrenia

Clozaril (clozapine) is a prescription medication approved by the U.S. Food and Drug Administration (FDA) for treating adults with schizophrenia.

How Clozaril Works and How It’s Taken

Clozaril is a type of medication called an atypical antipsychotic that works by blocking certain brain receptors, especially dopamine and serotonin receptors. The exact way it works is not fully known. In schizophrenia, this may help lower abnormal brain signaling linked to schizophrenia symptoms like confused thinking and false beliefs.

Doctors usually prescribe Clozaril for severe schizophrenia symptoms when standard antipsychotic medicines have not helped enough.

Clozapine is taken by mouth. It comes as a regular tablet, an orally disintegrating tablet that melts in the mouth, and an oral suspension called Versacloz. Clozaril is typically started once or twice daily and then increased gradually. It can be taken with or without food.

The recommended starting dose of Clozaril for schizophrenia is 12.5 milligrams once or twice daily.

For people who respond to treatment, the recommended maintenance dose is 150 milligrams to 225 milligrams twice daily.

Doctors may raise the dose by 25 milligrams to 50 milligrams per day at first, then by up to 100 milligrams once weekly or twice weekly. The maximum recommended dose is 450 milligrams twice daily.

If treatment needs to be stopped and the person does not have moderate or severe neutropenia (low white blood cells), doctors should reduce the dose gradually over one to two weeks rather than stopping it suddenly. Do not stop this medication abruptly without a doctor.

This information is based on the prescribing information, but your healthcare provider may tailor your treatment plan. Always follow their guidance.

Clozaril Side Effects

In clinical studies of Clozaril for treatment-resistant schizophrenia in adults, several side effects were commonly reported. Across the most common side effects listed below, rates were about 5 percent to 21 percent in the six-week clinical trial.

Sedation (sleepiness)
Tachycardia (fast heartbeat)
Constipation
Dizziness or vertigo
Hypotension (low blood pressure, which can make you feel lightheaded)
Fever
Hypersalivation (too much saliva or drooling)
Tremor
Syncope (fainting)
Sweating
Visual disturbances (vision problems)
Headache
Nausea or vomiting
Dry mouth

Serious Side Effects and Warnings

Clozaril can cause serious side effects that require immediate medical attention. These include:

Severe neutropenia — Very low neutrophils, a type of white blood cell, can lead to serious and potentially fatal infections.
Orthostatic hypotension, bradycardia, and syncope — A drop in blood pressure when standing, slow heart rate, and fainting can be life-threatening.
Seizures — Convulsions can cause sudden loss of consciousness.
Myocarditis, pericarditis, and cardiomyopathy — Serious heart inflammation or heart muscle weakness can be fatal.
Mitral valve incompetence — A leaky heart valve can let blood flow backward in the heart.
Falls — These can lead to fractures or other injuries.
Gastrointestinal hypomotility — Slowed gut movement can cause severe constipation, bowel blockage, or other serious complications.
Eosinophilia — High eosinophils, a type of white blood cell, can be linked to serious body-wide reactions.
QT interval prolongation and dangerous heart rhythm problems — Changes in heart rhythm can cause fainting, cardiac arrest, or sudden death.
Metabolic changes — High blood sugar, unhealthy cholesterol or triglycerides, and weight gain can raise heart and stroke risk.
Neuroleptic malignant syndrome (NMS) — This rare, life-threatening reaction can cause high fever, muscle stiffness, confusion, and unstable blood pressure or heart rate.
Hepatotoxicity — Serious liver injury, including liver failure, can occur.
Pulmonary embolism and deep vein thrombosis — Blood clots in the lungs or legs can occur.
Anticholinergic toxicity — This serious reaction can affect the brain and body and may worsen constipation or urinary retention.
Tardive dyskinesia — Possibly irreversible, uncontrolled movements can occur.
Recurrence of psychosis and cholinergic rebound after abrupt discontinuation — Symptoms may return, along with sweating, headache, nausea, vomiting, or diarrhea after suddenly stopping.
Increased risk of death in older adults with dementia-related psychosis — Clozaril is not approved to treat dementia-related psychosis.

Get medical help right away if you think you are having a serious reaction.

How To Save on Clozaril

No specific savings or copay assistance information was provided in the manuscript.

What To Know Before Taking Clozaril

Before starting Clozaril, your doctor will do a blood test to check your absolute neutrophil count (ANC).

Tell your doctor if you have any allergies to clozapine or any ingredients in Clozaril.

Tell your doctor about all medicines you take, including prescription drugs, over-the-counter medicines, and supplements.

Do not take Clozaril if you have had a serious allergic reaction to clozapine or any of its ingredients.

Clozaril is also FDA approved to reduce the risk of recurrent suicidal behavior in people with schizophrenia or schizoaffective disorder who are at chronic risk of suicidal behavior.

If you miss Clozaril for one day or more, call your doctor right away for instructions and do not restart at the same dose on your own.

If you are pregnant, planning to become pregnant, or breastfeeding while taking Clozaril, talk with your doctor about the risks and benefits. Babies exposed to Clozaril late in pregnancy may have movement or withdrawal symptoms after birth.

Clozapine can pass into breast milk. Because serious side effects are possible in breastfed babies, talk with your healthcare provider about whether to stop breastfeeding or stop taking clozapine.

Community FAQs

These answers are fact-checked by our editorial staff.

How effective is Clozaril?
In a six-week study of people with schizophrenia who had not responded adequately to at least three other antipsychotics, 30 percent of people taking Clozaril responded to treatment, compared with 4 percent of those taking chlorpromazine. In another study of people with schizophrenia or schizoaffective disorder who were at risk for recurrent suicidal behavior, 24 percent of those taking Clozaril had a significant suicide attempt or were hospitalized because of imminent suicide risk by week 104, compared with 32 percent of those taking olanzapine. These results show that Clozaril can help some people with hard-to-treat schizophrenia, but it does not work for everyone.

How long does Clozaril take to work for schizophrenia?
A six-week study showed treatment response by the end of six weeks in people with treatment-resistant schizophrenia. The information available does not give an exact timeline for when each person may start to notice improvement.

Can Clozaril cause sleepiness or make it hard to get out of bed when treating schizophrenia?
Yes. Sleepiness and sedation are common with Clozaril. In studies, drowsiness or sedation was reported in 39 percent of people overall, and sedation was reported in 21 percent of people in a six-week schizophrenia trial.

Can Clozaril be used with other medicines for schizophrenia?
Clozaril can interact with many other medicines. Some drugs can raise Clozaril levels, including strong CYP1A2 inhibitors such as fluvoxamine, ciprofloxacin, and enoxacin, while others can lower Clozaril levels, including tobacco smoke and strong CYP3A4 inducers such as carbamazepine, phenytoin, St. John’s wort, and rifampin.

People taking Clozaril should tell their healthcare provider about all prescription and over-the-counter medicines because dose changes may be needed, and some combinations are not recommended.