Warnings and Precautions of Effexor (Venlafaxine)

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Venlafaxine is an antidepressant drug in a class called serotonin-norepinephrine reuptake inhibitors (SNRIs). It is an oral tablet that comes in both an immediate-release (Effexor) and extended-release (Effexor XR) formula. Both are used to treat depression in addition to a variety of other mental health conditions.

SNRIs work by blocking the reabsorption (or reuptake) of serotonin and norepinephrine back into the nerve cells that released them. Blocking their reuptake increases the levels of these neurotransmitters in the brain. This improves your focus and alertness and boosts your mood.

Effexor has been discontinued in the U.S., but Effexor XR is still available by prescription. Unlike Effexor, Effexor XR only needs to be taken once a day.

Common 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

These side effects often improve over the first week or two as you continue taking the medication. Call your doctor if your symptoms become severe or don't go away.

Before Taking

Effexor should not be taken with or within two weeks of taking monoamine oxidase inhibitors (MAOIs). Examples of MAOIs include:

  • Emsam (selegiline)
  • Marplan (isocarboxazid)
  • Nardil (phenelzine)
  • Parnate (tranylcypromine)

Serious and even fatal complications may result from such a combination.


Make sure your doctor knows your complete medical history. Effexor should 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.

Warnings and Interactions

Warnings are established to both ensure the safe use and discontinuation of Effexor. Your doctor should monitor you for the following complications while you're taking Effexor.

Serotonin Syndrome

Be careful when mixing Effexor with other medicines that also affect serotonin levels, such as other antidepressants, lithium, and St. John's wort. Doing so can lead to an excessive serotonin buildup in the brain. This can cause a condition called serotonin syndrome.

Symptoms of serotonin syndrome include:

  • Confusion
  • Diarrhea
  • Dilated pupils
  • Fever
  • Loss of muscle coordination
  • Muscle stiffness
  • Sudden spikes in blood pressure or heart rate
  • Sweating or shivering
  • Twitching muscles
  • Unusual agitation or restlessness

Some cases of serotonin syndrome can be life-threatening. If you're taking Effexor and experience any of these symptoms, contact your doctor as soon as possible.

Risk of Overdose

You should always avoid drinking or using other drugs while you're taking Effexor. These substances may decrease the benefits of the medication, or they can result in a toxic overdose. The most common Effexor overdose effects include:

  • Changes in consciousness (ranging from sleepiness to coma)
  • Dilated pupils
  • Fast heart rate
  • Seizures
  • Vomiting

To reduce your risk of overdose, your doctor will only prescribe you the lowest possible dose in the smallest quantity.

Suicidal Thoughts and Actions

Children and adolescents (up to age 25) may experience increased suicidal thoughts and behaviors when taking antidepressant medications. The danger is greatest the first few months of treatment or when changing the dose.

Though this warning is true for all antidepressants, taking Effexor may increase your risk even more. A major study found that Effexor was associated with a higher risk of both completed and attempted suicide compared with other antidepressants, including Celexa (citalopram), Prozac (fluoxetine), and Prothiaden (dothiepin).

If you are having suicidal thoughts, contact the National Suicide Prevention Lifeline at 1-800-273-8255 for support and assistance from a trained counselor. If you or a loved one are in immediate danger, call 911.

For more mental health resources, see our National Helpline Database.

Discontinuation Syndrome

Stopping Effexor abruptly may result in one of more of the following withdrawal symptoms:

  • Anxiety or worsening of depression
  • Dizziness
  • Gastrointestinal upset
  • Headaches
  • Irritability
  • Nausea
  • Nightmares
  • Paresthesias (prickling, tingling sensation on the skin)
  • Vomiting

It's important to not stop taking Effexor on your own. If you and your doctor decide it's best for you to stop Effexor, they can provide you with a tapering strategy to minimize any withdrawal symptoms

A Word From Verywell

Before prescribing Effexor, your doctor will take a thorough medical history. Even so, it's important for you to play an active role in your care. Be sure to share every detail of your health history, regardless of whether or not you think it's important. 

Overall, Effexor is a well-tolerated medication that has helped many people cope with a variety of mental health conditions. You deserve to get well. The good news is that if Effexor doesn't help, there are lots of other options to try.

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6 Sources
Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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