See also Warning section. Drowsiness, dizziness, dry mouth, blurred vision, constipation, and trouble sleeping may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly. To reduce the risk of dizziness and lightheadedness, get up slowly when rising from a sitting or lying position. This drug may cause muscle/nervous system problems (extrapyramidal symptoms-EPS). Your doctor may prescribe another medication to decrease these side effects. Therefore, tell your doctor immediately if you notice any of the following side effects: stiff muscles, severe muscle spasms/cramping (such as twisting neck, arching back, eyes rolling up), restlessness/constant need to move, shaking (tremor), slow/shuffling walk, drooling/trouble swallowing, mask-like expression of the face. 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 taking this medication do not have serious side effects. Tell your doctor immediately if any of these unlikely but serious side effects occur: fainting, fast heartbeat, depression/suicidal thoughts, difficulty urinating. This medication may cause a condition known as tardive dyskinesia. In some cases, this condition may be permanent. Tell your doctor immediately if you develop any involuntary/repetitive muscle movements such as lip smacking/puckering, tongue thrusting, chewing, or finger/toe movements. In rare cases, thiothixene 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 immediately. Tell your doctor immediately if any of these rare but very serious side effects occur: easy bruising/bleeding, signs of infection (such as fever, persistent sore throat), severe stomach/abdominal pain, seizures. This medication may rarely cause a serious condition called neuroleptic malignant syndrome (NMS). Seek immediate medical attention if you develop the following: fever, stiff muscles, sweating, fast/irregular heartbeat, sudden mental/mood changes (such as confusion, loss of consciousness), change in the amount of urine. A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: 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. In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.