Warnings of Effexor (Venlafaxine) for Depression

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Effexor (generic name: venlafaxine) is an antidepressant that is also sold in an extended-release form as Effexor XR.

Effexor is in a class of antidepressants called serotonin-norepinephrine reuptake inhibitors (SNRIs). It's not related to other antidepressants, such as the selective serotonin reuptake inhibitors (SSRIs) 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 so-called 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.


The most 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 seven days after discontinuing either form of Effexor before starting an MAOI.


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. Withdrawal syndrome, which may be severe and prolonged, 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:

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

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:

  • Loss of appetite
  • Nausea
  • Vomiting
  • Diarrhea
  • Headache
  • Nightmares
  • Feeling tired
  • Constipation
  • Gas
  • Heartburn
  • Drowsiness

Other Precautions

Make sure your doctor knows your complete medical history. Effexor may not be a good choice if you have:

  • Brain Disease or Damage, or Mental Retardation, 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 make these conditions worse.
  • 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.
  • A 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.

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 effects of this medication to kick in.
  • Take as directed, 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 of side effects when taking any over-the-counter medications with Effexor or Effexor XR.
  • Nausea is the most commonly reported side effect. The manufacturer says this will usually diminish within two 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, but if a large weight loss occurs, it may be harmful to some patients. 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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Article Sources

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  1. Shelton RC. Serotonin and Norepinephrine Reuptake Inhibitors. Handb Exp Pharmacol. 2019;250:145-180. doi:10.1007/164_2018_164

  2. U.S. Food and Drug Administration. Effexor XR (venlafaxine Extended-Release) Capsules. Updated 2017.

  3. U.S. Food and Drug Administration. Effexor. Updated 2006.

  4. Ye C, Ninneman M, Christian JS, Zhang F, Musselman D. Seizure Induced by a Therapeutic Dose of Venlafaxine ER: A Case Report. J Psychiatr Pract. 2018;24(2):117-120. doi:10.1097/PRA.0000000000000298

  5. Patel R, Reiss P, Shetty H, et al. Do antidepressants increase the risk of mania and bipolar disorder in people with depression? A retrospective electronic case register cohort study. BMJ Open. 2015;5(12):e008341. doi:10.1136/bmjopen-2015-008341

Additional Reading

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