Generic name: Clozapine.

Clozaril is an antipsychotic. It works by calming certain areas of the brain while enabling the rest of the brain to function properly, screening the transmission of some nerve impulses but restricting others. 

Quick Facts About Clozaril


Used to treat severe schizophrenia in cases where standard treatments have failed.

Clozaril Dosage

Take exactly as directed. Clozaril is distributed only via the Clozaril Patient Management Systems, ensuring weekly testing prior to the delivery of the pill supply.

  • Usual adult dose: 1/2 of a 25-milligram tablet (12.5 milligrams) 1 or 2 times per day. Doctor may increase in increments of 25 to 50 milligrams a day, up to 300 to 450 milligrams per day total, by the end of 2 weeks. Dosage may increase up to 900 milligrams per day, at weekly increments of 100 milligrams.
  • Usual child dose: not prescribed for children under 16 years.
  • Missed dose: take as soon as possible, unless almost time for next dose. In that case, do not take missed dose; go back to regular schedule. Do not double doses.

Clozaril Side Effects

Overdose symptoms:

coma, delirium, drowsiness, excess salivation, faintness, low blood pressure, rapid heartbeat, seizures, shallow breathing. If you suspect an overdose, immediately seek medical attention.

More common side effects: abdominal discomfort, agitated state, constipation, disturbed sleep, dizziness, drowsiness, dry mouth, fainting, fever, headache, heartburn, high blood pressure, loss of muscle movement, low blood pressure, nausea, nightmares, rapid heartbeat and other heart conditions, restlessness, salivation, sedation, sweating, tremors, vertigo, vision problems, weight gain.

Less common Clozaril side effects: bdominal distension, abnormal stools, anemia, anxiety, appetite increase, back pain, belching, bitter taste, blood clots, bloodshot eyes, bluish tinge to the skin, breast pain or discomfort, bronchitis, chills, confusion, constant involuntary eye movement, coughing, depression, diarrhea, difficult or labored breathing, dilated pupils, disorientation, dry throat, ear disorders, ejaculation problems, excessive movement, eyelid disorder, fast or fluttery heartbeat, fatigue, fluid retention, frequent urination, hallucinations, hives, hot flashes, impotence, inability to sit down, inability to urinate, increase or decrease in sex drive, inflamed stomach and intestines, involuntary movement, irritability, itching, jerky movements, joint pain, lack of coordination, leg pain, lethargy, light-headedness, loss of appetite, loss of speech, low body temperature, memory loss, muscle pain or ache, muscle spasm, muscle weakness, neck pain, nervous stomach, nosebleed, numbness, painful menstruation, pallor, paranoia, pneumonia-like symptoms, poor coordination, rapid breathing, rash, rectal bleeding, rigidity, runny nose, seizures, severe chest pain, shakiness, shortness of breath, skin inflammation, redness, scaling, sleeplessness, slow heartbeat, slurred speech, sneezing, sore throat, sore or numb tongue, stomach pain, stomach ulcer, stuffy nose, stupor, stuttering, thirst, throat discomfort, twitching, urination problems, vaginal infection, vaginal itch, vague feeling of sickness, vomiting, vomiting blood, weakness, wheezing.


Inform your doctor before combining Clozaril with:

blood pressure medications such as Aldomet; Cimetidine (Tagamet): Digoxin (Lanoxin): drugs that affect the central nervous system such as Valium, Xanax, and Seconal; drugs that contain atropine such as Donnatal and Levsin; epilepsy drugs such as Tegretol and Dilantin; Epinephrine; other antipsychotic and mood-altering medications; Warfarin (Coumadin).

No known food/other substance interactions. 

Special Cautions

If pregnant or planning to become pregnant, inform your doctor immediately. Clozaril should be discontinued during pregnancy unless absolutely necessary. May appear in breast milk; could affect a nursing baby.

No special precautions apply to seniors.

Not prescribed for children under 16 years.

  • May cause granulocytosis, a potentially fatal white blood cell disorder; approximately 1 % develop this disorder and must stop taking Clozaril. As a result, the medication is carefully controlled through weekly blood tests.
  • Before receiving the following week’s supply of medication, the blood cell counts must be normal. Early warning signs include: fever, general feeling of illness, flu-like feeling, lethargy, sore throat, ulcer of the lips, ulcer of the mouth or mucous membranes, or weakness.
  • May cause drowsiness or seizures and impair your ability to drive a car or operate machinery, swim or climb. Do not take part in any activity that requires alertness.
  • Seizures occur in approximately 5% of people who take Clozaril. The higher the dosage, the higher the risk of seizure.
  • Because of the risks of taking Clozaril, it should only be prescribed when other antipsychotic medications such as Haldol or Mellaril have not worked.
  • Should not take Clozaril if you have: abnormal white blood cell count, bone marrow disease or disorder, or if you are taking drugs that could decrease your white blood cell count such as Tegretol.
  • Doctor should monitor if you have: enlarged prostate; history of seizures; kidney, liver, lung, or heart disease; or narrow-angle glaucoma.
  • Clozaril may cause Neuroleptic Malignant Syndrome; symptoms include: changes in heart rhythm, excessive perspiration, high fever, irregular pulse or blood pressure, muscle rigidity, or rapid heartbeat.

Note: provides accurate and independent information prescription pills, over-the-counter medicines and natural products. This material is provided for educational purposes only and is not intended for medical advice, diagnosis or treatment. If you have questions about  dosage, or Clozaril side effects, please contact your healthcare provider.