Dizziness, lightheadedness, drowsiness, difficulty urinating, sleep disturbances, headache, and anxiety may occur. If these effects persist or worsen, notify your doctor or pharmacist promptly.
Dizziness and lightheadedness can increase the risk of falling. Get up slowly when rising from a sitting or lying position.
Tell your doctor promptly if any of these side effects occur: muscle spasm/stiffness, shaking (tremor), restlessness, mask-like facial expression, drooling. Your doctor may prescribe another medication for you to take with haloperidol to decrease these side effects.
Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
In rare cases, haloperidol may increase your level of a certain chemical made by the body (prolactin). For females, this increase in prolactin may result in unwanted breast milk, missed/stopped periods, or difficulty becoming pregnant. For males, it may result in decreased sexual ability, inability to produce sperm, or enlarged breasts. If you develop any of these symptoms, tell your doctor right away.
For males, in the unlikely event you have a painful or prolonged erection (lasting more than 4 hours), stop using this drug and seek immediate medical attention, or permanent problems may occur.
This medication may rarely cause a condition known as tardive dyskinesia. In some cases, this condition may be permanent. Tell your doctor right away if you develop any facial/muscle twitching such as tongue thrusting, chewing movements, puffing or puckering of your mouth, or uncontrollable shaking.
This medication may rarely cause a very serious condition called neuroleptic malignant syndrome (NMS). Get medical help right away if you have any of the following symptoms: fever, muscle stiffness/pain/tenderness/weakness, severe tiredness, severe confusion, sweating, fast/irregular heartbeat, dark urine, signs of kidney problems (such as change in the amount of urine).
Tell your doctor right away if any of these rare but very serious side effects occur: persistent nausea/vomiting, stomach/abdominal pain, yellowing of eyes/skin, seizures, signs of infection (such as fever, persistent sore throat).
Seek immediate medical attention if any of these rare but very serious side effects occur: slow heartbeat, severe dizziness, chest pain, fainting.
A very severe allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of an allergic reaction include: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.
This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.
In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.
In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.