Clozaril side effects: clear, practical advice

Clozaril (clozapine) can help when other antipsychotics fail, but it has some serious side effects you should know about. One of the most important facts: the drug carries about a 1% risk of severe drop in white blood cells (agranulocytosis), so blood checks are not optional—they're lifesaving.

Key side effects and what they look like

Agranulocytosis/neutropenia: watch for fever, sore throat, mouth sores, or unexplained infections. If you get these, call your prescriber and get blood tests right away. Monitoring rules usually require a baseline WBC/ANC, then weekly blood tests for the first 6 months, every 2 weeks for months 7–12, and monthly after that.

Myocarditis and cardiomyopathy: rare but serious, often in the first month. Symptoms include chest pain, fast heartbeat, breathlessness, or flu-like fatigue. Report these immediately—doctors will check troponin, ECG, and possibly an echo.

Seizures: risk rises with higher doses (notably above 600 mg/day) and with rapid dose increases. Tell your provider if you have a seizure history; they may adjust the dose or add precautions.

Metabolic issues and weight gain: clozapine often causes significant weight gain, raised blood sugar, and higher cholesterol. Expect regular glucose and lipid checks and plan lifestyle steps (diet, activity) to reduce long-term risk.

Other common effects: sedation, heavy saliva (hypersalivation), constipation (can be severe), low blood pressure when standing (orthostatic hypotension), and rapid heart rate. Severe constipation can be dangerous—seek help if no bowel movement for several days or if you have severe abdominal pain.

When to call your doctor and how to reduce risks

Call right away if you have fever, sore throat, new cough, mouth ulcers, chest pain, sudden shortness of breath, severe abdominal pain, or a seizure. Don’t wait for scheduled tests when these appear.

Practical risk-reduction tips: follow the blood-test schedule exactly; avoid stopping the drug suddenly; tell any provider if you start or stop smoking (smoking lowers clozapine levels via CYP1A2); check with your prescriber before starting antibiotics like ciprofloxacin or fluvoxamine—some drugs raise clozapine levels and increase side effects. Avoid combining high doses with other sedatives without medical advice.

Keep a simple checklist: track your blood test dates, note any new symptoms, weigh yourself weekly, and ask for baseline and regular ECG/glucose checks. If you or a family member are starting Clozaril, make sure the clinic is enrolled in the monitoring program used in your country—this keeps care safe and on schedule.

This is practical information, not medical advice. Talk to your prescriber about your personal risks and the exact monitoring plan you’ll follow while on clozapine.