Effexor XR Oral Side Effects
See also Warning section.
Headache, drowsiness, dizziness, nausea, weakness, dry mouth, constipation, loss of appetite, weight loss, blurred vision, tiredness, nervousness, trouble sleeping, sweating, or yawning may occur. If any of these effects persist or worsen, tell your doctor promptly.
If you are using the tablet form of this medication, an empty tablet shell may appear in your stool. This effect is harmless because your body has already absorbed the medication.
Venlafaxine may increase blood pressure. Your blood pressure should be checked regularly while you are taking this medication.
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: severe/pounding headache, unusual or severe mental/mood changes (e.g., extreme anxiety, unusual high energy/excitement, rare thoughts of suicide), shakiness (tremor), decreased interest in sex, changes in sexual ability, difficulty urinating, change in the amount of urine.
Tell your doctor immediately if any of these rare but very serious side effects occur: stomach/abdominal pain, chest pain, persistent cough, shortness of breath, bloody/black/tarry stools, vomit that looks like coffee grounds, easy bruising/bleeding, fast/irregular/pounding heartbeat, muscle weakness/cramps, yellowing eyes/skin, dark urine, seizures, unusual tiredness.
This medication may rarely cause a very serious condition called serotonin syndrome. The risk increases when this medication is used with certain other drugs such as “triptans” used to treat migraine headaches (e.g., sumatriptan, eletriptan), certain antidepressants including SSRIs (e.g., citalopram, paroxetine) and other SNRIs (e.g., duloxetine), lithium, tramadol, tryptophan, or a certain drug to treat obesity (sibutramine). See also 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: hallucinations, fainting, 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.