See also Warning section. Nausea, vomiting, loss of appetite, upset stomach, drowsiness, dizziness, diarrhea, trouble sleeping, and sweating may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly. 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: easy bruising/bleeding, unusual or severe mental/mood changes (e.g., agitation, thoughts of suicide), weakness, muscle stiffness/pain, uncontrolled movements (e.g., shaking), decrease in sexual interest/ability, fast/pounding heartbeat, unusual tiredness, increased/painful urination, tingling or numbness of the hands/feet. Tell your doctor immediately if any of these rare but very serious side effects occur: change in the amount of urine, seizures, black/bloody stools, vomit that looks like coffee grounds, fainting. This medication may rarely cause a very serious condition called serotonin syndrome. The risk increases when this medication is used with certain other drugs (See Drug Interactions section). Before taking this drug, tell your doctor if you take any of these medications. Serotonin syndrome may be more likely when you start or increase the dose of any of these medications. Seek immediate medical attention if you develop some of the following symptoms: hearing/seeing things that are not there (hallucinations), unusual restlessness, loss of coordination, fast heartbeat, severe dizziness, unexplained fever, severe nausea/vomiting/diarrhea, twitchy muscles. For males, in the very unlikely event you have a painful or prolonged erection lasting 4 or more 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.