See also Warning and Side Effects sections.

Before taking clozapine, tell your doctor or pharmacist if you are allergic to it or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: history of blood disorders (such as leukemia, low white blood cell count), bowel problems (such as paralytic ileus, irritable bowel syndrome ), breathing problems, diabetes/family history of diabetes, high cholesterol/triglyceride levels, glaucoma, heart problems, kidney problems, liver problems, obesity/family history of obesity, seizures, difficulty urinating (for example, due to enlarged prostate), breathing trouble during sleep (sleep apnea).

Clozapine may cause a condition that affects the heart rhythm (QT prolongation). QT prolongation can rarely cause serious (rarely fatal) fast/irregular heartbeat and other symptoms (such as severe dizziness, fainting) that need medical attention right away.

The risk of QT prolongation may be increased if you have certain medical conditions or are taking other drugs that may affect the heart rhythm. Before using clozapine, tell your doctor or pharmacist of all the drugs you take and if you have any of the following conditions: certain heart problems (heart failure, slow heartbeat, QT prolongation in the EKG), family history of certain heart problems (QT prolongation in the EKG, sudden cardiac death).

Low levels of potassium or magnesium in the blood may also increase your risk of QT prolongation. This risk may increase if you use certain drugs (such as diuretics/"water pills") or if you have conditions such as severe sweating, diarrhea, or vomiting. Talk to your doctor about using clozapine safely.

This drug may make you dizzy or drowsy or blur your vision. Alcohol or marijuana (cannabis) can make you more dizzy or drowsy. Do not drive, use machinery, or do anything that needs alertness or clear vision until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

Tell your doctor if you are a descendent of Ashkenazi Jews because you may be at a higher risk for a drop in your white blood cells.

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

Liquid products or dissolving tablets may contain sugar and/or aspartame. Liquid products may also contain alcohol. Caution is advised if you have diabetes, liver disease, phenylketonuria (PKU), or any other condition that requires you to limit/avoid these substances in your diet. Ask your doctor or pharmacist about using this product safely.

Older adults may be more sensitive to the side effects of this drug, especially constipation, trouble urinating, drowsiness, dizziness, lightheadedness, and QT prolongation (see above). Drowsiness, dizziness, and lightheadedness can increase the risk of falling.

During pregnancy, this medication should be used only when clearly needed. Babies born to mothers who have used this drug during the last 3 months of pregnancy may rarely develop symptoms including muscle stiffness or shakiness, drowsiness, feeding/breathing difficulties, or constant crying. If you notice any of these symptoms in your newborn especially during their first month, tell the doctor right away.

Since untreated mental/mood problems (such as schizophrenia, schizoaffective disorders) can be a serious condition, do not stop taking this medication unless directed by your doctor. If you are planning pregnancy, become pregnant, or think you may be pregnant, immediately discuss with your doctor the benefits and risks of using this medication during pregnancy.

Clozapine passes into breast milk and may have undesirable effects on a nursing infant. Breastfeeding is not recommended while using this medication. Consult your doctor before breastfeeding.