• If you are allergic to anything, including medicines, dyes, additives, or foods.

• If you have ever had seizures, have an abnormal EEG (brain waves) or are taking anti-seizure medicines. This drug may raise your risk of seizures.

• If you have prostate enlargement or glaucoma. This drug can worsen your symptoms.

• If you have thyroid problems. Haloperidol can cause nervous system problems including rigid muscles and inability to walk and talk.

• If you have an abnormal heart rhythm, heart block, heart failure, or any problem with the heart's electrical system. Haloperidol can slow down the heart's electrical impulses and make these problems worse. It can also lower the blood pressure and deprive the heart of oxygen.

• If you have low potassium or low magnesium, or if you are taking medicines such as diuretics ("water pills") that may cause your potassium or magnesium levels to drop. Haloperidol can slow down the heart's electrical impulses and these problems may make it more dangerous.

• If you have taken chemotherapy drugs that can damage the heart, such as daunorubicin, doxorubicin, epirubicin, or idarubicin. These medicines may worsen the effects on the heart.

• If you take tranquilizers (sedatives) such as diazepam (Valium) or drink a lot of alcohol. This may increase the chance of the heart rhythm problem mentioned above.

• If you have liver or kidney disease. Haloperidol can pose a higher risk of side effects if these are present.

• If you are pregnant, trying to get pregnant, or if there is any chance of pregnancy. There may be an increased risk of harm to the fetus if a woman takes this drug during pregnancy.

• If you are breast-feeding. It is not known whether this drug passes into breast milk. If it does, it could harm the baby.

• About any other prescription or over-the-counter medicines you are taking, including vitamins and herbs.

Rifampin may lower the level of haloperidol in the body so that the haloperidol does not work.

If lithium is taken with this drug, it may cause weakness, fever, tremor, confusion, involuntary movements. If this syndrome is not treated quickly, brain damage can result.

Epinephrine may lower the blood pressure (rather than raise it) if it is taken with haloperidol. The doctor can substitute another drug if epinephrine's effects are needed.

Medicines for Parkinson's disease may increase the pressure inside the eyeball if taken with haloperidol.

Anticoagulants (blood thinners) may not work properly. You may need more monitoring or dose adjustments while you are on haloperidol.

Medicines that make you sleepy, such as tranquilizers, opioid pain relievers, anesthetics, and sleeping pills will make you much sleepier and may cause harm when taken with haloperidol.

Check with your doctor, nurse, or pharmacist about whether any of the medicines, vitamins, herbs, and supplements you are taking can cause problems with haloperidol.

Haloperidol may cause unplanned movements called extrapyramidal effects. These include restlessness, tremors, sticking out the tongue, and involuntary (unplanned) muscle contractions. Let your doctor or nurse know right away if this happens. These side effects can usually be stopped by other medicines such as diphenhydramine (Benadryl). In some cases, it may be necessary to stop the haloperidol.

Be careful getting up, changing position, or walking. Start slowly and hold onto something or someone to keep you steady. Have a responsible adult with you until the medicine has completely worn off.

Call your doctor or nurse if you have restlessness, muscle stiffness, severe anxiety, slow jerky movements, tiredness, weakness, fast or irregular heartbeat, or yellow eyes or skin.

In rare cases, haloperidol can cause changes in the heart's rhythm, some of which can be dangerous. Get emergency help if you have irregular heart beat, blue nail beds or skin, gasping for breath, or seizure.

This drug can turn your urine pink or reddish brown, and is not a harmful effect. It goes away when you stop the drug.

• feeling calm (sedated)
• sleepiness

• decreased breathing rate
• increased heart rate*
• decrease in blood pressure when changing position*
• low blood pressure*
• restlessness, agitation

• dry mouth
• trouble urinating
• blurred vision
• constipation
• unplanned (involuntary) movements, extrapyramidal effects*
• change in electrical impulses in the heart, which can be serious*
• increased sensitivity to sun, easier to burn
• damage to liver, with yellow eyes or skin*

*See "Precautions" section for more detailed information.