Venlafaxine

Venlafaxine
(VEN-la-fax-een)

Effexor

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Venlafaxine is used to treat depression. It may improve your mood and energy level, and may help restore your interest in daily living. Venlafaxine is known as a serotonin-norepinephrine reuptake inhibitor (SNRI). It works by helping to restore the balance of certain natural substances (serotonin and norepinephrine) in the brain.

This medication may also be used to treat anxiety, panic attacks, and nerve pain. It may also be used to treat hot flashes that occur with menopause.

It may take several weeks to feel the benefit of this medication. Tell your doctor if your condition persists or worsens.

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Some products that may interact with this drug include: other drugs that can cause bleeding/bruising (including antiplatelet drugs such as clopidogrel, NSAIDs such as ibuprofen, "blood thinners" such as warfarin).

Taking MAO inhibitors with this medication may cause a serious (possibly fatal) drug interaction. Avoid taking MAO inhibitors (isocarboxazid, linezolid, methylene blue, moclobemide, phenelzine, procarbazine, rasagiline, selegiline, tranylcypromine) during treatment with this medication. Most MAO inhibitors should also not be taken for two weeks before and at least 7 days after treatment with this medication. Ask your doctor when to start or stop taking this medication.

The risk of serotonin syndrome/toxicity increases if you are also taking other drugs that increase serotonin. Examples include street drugs such as MDMA/"ecstasy," St. John's wort, certain antidepressants (including SSRIs such as fluoxetine/paroxetine, other SNRIs such as desvenlafaxine/duloxetine), tryptophan, among others. The risk of serotonin syndrome/toxicity may be more likely when you start or increase the dose of these drugs.

Tell your doctor or pharmacist if you are taking other products that cause drowsiness including alcohol, antihistamines (such as cetirizine, diphenhydramine), drugs for sleep or anxiety (such as alprazolam, diazepam, zolpidem), muscle relaxants, and narcotic pain relievers (such as codeine). Check the labels on all your medicines (such as allergy or cough-and-cold products) because they may contain ingredients that cause drowsiness. Ask your pharmacist about using those products safely.

Aspirin can increase the risk of bleeding when used with this medication. However, if your doctor has directed you to take low-dose aspirin for heart attack or stroke prevention (usually at dosages of 81-325 milligrams a day), you should continue taking it unless your doctor instructs you otherwise.

Venlafaxine is very similar to desvenlafaxine. Do not take medications containing desvenlafaxine while using venlafaxine.

This medication may interfere with certain laboratory tests (including urine tests for amphetamines), possibly causing false test results. Make sure laboratory personnel and all your doctors know you use this drug.

Common side effects of Venlafaxine include:

  • Nausea
  • Drowsiness
  • Dizziness
  • Dry mouth
  • Constipation
  • Loss of appetite
  • Blurred vision
  • Nervousness
  • Trouble sleeping
  • Unusual sweating
  • Yawning

If any of these effects persist or worsen, tell your doctor promptly.

Tell your doctor right away if any of these unlikely but serious side effects occur: easy bruising/bleeding, decreased interest in sex, changes in sexual ability, muscle cramps/weakness, shaking (tremor).

Get medical help right away if any of these rare but serious side effects occur: black/bloody stools, persistent cough, seizure, severe/pounding headache, shortness of breath, vomit that looks like coffee grounds.

This medication may increase serotonin and rarely cause a very serious condition called serotonin syndrome/toxicity. The risk increases if you are also taking other drugs that increase serotonin, so tell your doctor or pharmacist of all the drugs you take (see Drug Interactions section). Get medical help right away if you develop some of the following symptoms: fast heartbeat, hallucinations, loss of coordination, severe dizziness, severe nausea/vomiting/diarrhea, twitching muscles, unexplained fever, unusual agitation/restlessness.

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.