Warnings and Precautions When Using Effexor (Venlafaxine)

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Effexor (venlafaxine) is an antidepressant that is generally prescribed in an extended-release form as Effexor XR.

Effexor is in a class of antidepressants called serotonin-norepinephrine reuptake inhibitors (SNRIs). Other categories of antidepressants include selective serotonin reuptake inhibitors (SSRIs) such as Prozac (fluoxetine) and Zoloft (sertraline), or tricyclic antidepressants such as Elavil (amitriptyline).

Effexor appears to work by preventing your body from re-absorbing two different chemicals used to transmit nerve signals: serotonin and norepinephrine. These two neurotransmitters play an important role in determining a person's mood. The extended-release form of the drug, Effexor XR, is also prescribed for generalized anxiety disorder, panic disorder, and social anxiety disorder.

Effexor Warnings

One important thing to know before taking Effexor is that it must not be used in combination with another type of antidepressants called monoamine oxidase inhibitors (MAOIs) such as Nardil (phenelzine), Marplan (isocarboxazid), and Parnate. Serious and even fatal complications may result from such a combination.

In addition, wait 14 days after discontinuing the MAOI drug before starting Effexor or Effexor XR, and wait at least seven days after discontinuing either form of Effexor before starting an MAOI.

Withdrawal From Effexor

It's best to start at a low dose of Effexor and build up to the desired strength gradually. Don't ever stop Effexor abruptly. A withdrawal syndrome, which may be severe, can occur even if the medication is tapered off, so be sure to work with your doctor if you need to go off of Effexor. Symptoms of withdrawal may include:

  • Bizarre dreams
  • Dizziness
  • Gastrointestinal upset
  • Headaches
  • Nausea
  • Paresthesias (abnormal sensations of burning, prickling, tingling, etc.)
  • Recurrence of depression
  • Unstable moods

Effexor Side Effects

Like any medication, side effects may occur while taking Effexor. Be sure to contact your doctor if they don't go away or become bothersome. Common side effects include:

  • Constipation
  • Diarrhea
  • Drowsiness
  • Feeling tired
  • Headache
  • Heartburn
  • Loss of appetite
  • Nausea
  • Sexual side effects
  • Vomiting

Other Precautions

Make sure your doctor knows your complete medical history. Effexor may need to be used with caution if you have:

  • Brain disease or damage, or a history of seizures: The risk of seizures may be increased when taking Effexor.
  • Heart disease or high or low blood pressure: Effexor may occasionally make these conditions worse.
  • History of mania: The risk of developing mania may be increased while taking Effexor. Obviously, this is very important for bipolar patients to watch for.
  • Kidney disease or liver disease: Higher blood levels of Effexor may occur, increasing the chance of side effects. Your doctor may need to adjust your dose.

Other Important Facts

These facts may be important to be aware of if you're taking or plan to take Effexor. It may take several weeks for the full effects of this medication to kick in. You should always take Effexor as directed, generally with food, and do not break, crush or chew tablets or open the capsules. If you miss a dose, do not take a double dose to make up.

Be cautious and let your doctor know when taking any over-the-counter medications with Effexor or Effexor XR. Nausea is the most commonly reported side effect. This will usually diminish within 2 weeks. Animal test results show that the use of Effexor while pregnant or nursing may not be wise. Talk to your doctor about weighing the risks versus the benefits.

Effexor and Effexor XR may cause weight loss. This weight loss is usually small. Talk to your doctor about this if you're concerned or if you start losing too much weight. Alcohol can increase the feeling of drowsiness this medication may cause.

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Additional Reading
  • "Venlafaxine." MedLine Plus, U.S. National Library of Medicine (2014).