Drowsiness, dizziness, dry mouth, blurred vision, tiredness, constipation, weight gain, 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. Tell your doctor immediately if you notice any of the following side effects: feelings of anxiety/agitation/jitteriness, drooling/trouble swallowing, restlessness/constant need to move, shaking (tremor), shuffling walk, stiff muscles, severe muscle spasms/cramping (such as twisting neck, arching back, eyes rolling up), 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 using this medication do not have serious side effects. Tell your doctor immediately if any of these unlikely but serious side effects occur: difficulty urinating, sunburn-like rash (sun sensitivity), decreased cough reflex, swelling of the feet/ankles, butterfly-shaped rash on nose and cheeks, joint/muscle pain, skin discoloration, eye/vision changes, feeling unusually cold or hot, muscle weakness. Infrequently, this medication may cause face/muscle twitching and uncontrollable movements (tardive dyskinesia). In some cases, this condition may be permanent. Tell your doctor immediately if you develop any uncontrollable movements such as lip smacking, mouth puckering, tongue thrusting, chewing, or unusual arm/leg movements. In rare cases, trifluoperazine 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. Rarely, males may have a painful or prolonged erection lasting 4 or more hours. If this occurs, stop using this drug and seek immediate medical attention, or permanent problems could occur. Tell your doctor immediately if any of these rare but serious side effects occur: signs of liver problems (such as yellowing eyes/skin, dark urine, persistent nausea, vomiting, stomach/abdominal pain), signs of infection (such as fever, persistent sore throat), easy bruising/bleeding, signs of anemia (such as severe tiredness, fast breathing, pale skin, fast heartbeat), mental/mood changes (such as worsening psychosis, unresponsive/catatonic state). Seek immediate medical attention if any of these rare but serious side effects occur: slowed breathing, chest pain, seizures. This drug may rarely cause a serious (sometimes fatal) nervous system problem (neuroleptic malignant syndrome-NMS). Seek immediate medical attention if you notice any of the following side effects: fever, stiff muscles, increased 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.