Drowsiness, dizziness, lightheadedness, abdominal/stomach pain, weight gain, cough, or dry mouth may occur. If any of these side effects persist or worsen, tell your doctor promptly. To reduce the risk of dizziness and lightheadedness, get up slowly when rising from a sitting or lying position. These side effects are more likely to occur in the first few days after starting/restarting the drug or after your dose increases. An empty tablet shell may appear in your stool. This is harmless. 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 swallowing, fast/slow/irregular heartbeat, restlessness, shaking (tremor), muscle spasms, pain/swelling/redness of arms or legs, signs of infection (such as fever, persistent sore throat). Seek immediate medical attention if any of these rare but very serious side effects occur: seizures, fainting, weakness on one side of the body, slurred speech, chest pain, confusion, vision changes, trouble breathing. Paliperidone may rarely cause a condition known as tardive dyskinesia. In some cases, this condition may be permanent. Tell your doctor immediately if you develop any unusual/uncontrolled movements (especially of the face, lips, mouth, tongue, arms, or legs). This drug may infrequently cause a serious (rarely fatal) nervous system disorder (neuroleptic malignant syndrome). Seek immediate medical attention if you notice any of the following rare but very serious side effects: muscle stiffness/pain, high fever, increased sweating, mental/mood changes, change in the amount of urine. Rarely, this medication may increase your blood level of a certain hormone (prolactin). In females, an increase in prolactin levels may result in unwanted breast milk, missed/stopped periods, or difficulty becoming pregnant. In 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. For males, in the very 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 could occur. 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.