Effexor, also known as venlafaxine, is classified as a selective serotonin and norepinephrine reuptake inhibitor (SSRI). It increases levels of serotonin and norepinephrine, brain chemicals that regulate mood. For this reason, Effexor is prescribed in the treatment of depression. Patients typically must take the drug for up to two months before it becomes fully effective, according to the National Library of Medicine. Effexor should not be taken in conjunction with monoamine oxidase inhibitors, which are also prescribed for depression. Patients taking a monoamine oxidase inhibitor should notify their doctor to avoid harmful drug interactions.
Common Side Effects of Effexor
The Merck Manual notes that because Effexor increases the amount of serotonin in the brain, the excess serotonin may cause sexual dysfunction, headache and insomnia. It may also cause nausea which is the most common side effect experienced by patients taking Effexor. Nausea usually goes away within a couple of weeks after starting treatment. Other gastrointestinal side effects include vomiting, stomach pain, constipation, diarrhea, gas, heartburn and burping. Neurological side effects include dizziness, numbness, nightmares and anxiety. Less common are chills, fever, and enlarged pupils. Some patients may have increased urge to urinate or difficulty urinating.
Serious Side Effects of Effexor
Some patients may experience a severe allergic reaction to Effexor. Symptoms of an adverse reaction to the drug include rashes, itching, trouble breathing and difficulty swallowing. Patients experiencing any of these symptoms should seek medical attention immediately. Serious cardiac side effects may also occur. The Mayo Clinic lists these as chest pain, irregular heartbeat and increased blood pressure. Severe neurological side effects include seizures, temporary loss of consciousness, hallucinations and ringing in the ears. In addition, Effexor has been known to cause vision changes such as blurring and pain or redness of the eye. A physician should be consulted regarding any of these side effects.
Overdose Side Effects of Effexor
Patients taking Effexor are instructed to not take more or less than exactly what is prescribed. The National Library of Medicine warns that if a dose is missed, do not try to make up for it if the time for the next dose is near. An excess of Effexor in the body can cause life-threatening side effects. These include nausea, vomiting and agitation. Heartbeat may become irregular and the patient may experience hot and cold spells. Numbness in extremities, muscle pain and trembling (possibly seizures) can occur. Finally, the patient may feel extremely drowsy and slip into a coma. If any of these side effects occur, the poison control center or 911 should be called immediately.
