Warnings and Precautions of Effexor (Venlafaxine)

Venlafaxine is an antidepressant in the serotonin norepinephrine reuptake inhibitor (SNRI) class. It is an oral tablet that comes in an immediate-release (Effexor) and prolonged-release (Effexor XR) formulation. Both are used to treat depression in addition to a variety of other mental health issues.

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

Effexor has been discontinued in the United States, but Effexor XR is still available by prescription. Unlike Effexor, Effexor XR should only be taken once a day.

Common side effects

Like any medicine, side effects can occur when 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
  • Stomach pains
  • Loss of appetite
  • Nausea
  • Sexual side effects
  • Vomiting

These side effects often get better in the first week or two as you continue to take the medicine. Call your doctor if your symptoms get worse or do not go away.

Before taking

Effexor should not be taken with or within two weeks of taking monoamine oxidase inhibitors (MAOIs). Here are some examples of AMOI:

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

Serious and even fatal complications can 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 can occasionally make these conditions worse.
  • History of mania: The risk of developing mania may be increased when taking Effexor. Obviously, this is very important for bipolar patients to watch out for.
  • Kidney disease or liver disease: Higher blood levels of Effexor may occur, which increases the risk of side effects. Your doctor may need to adjust your dose.

Warnings and interactions

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

Serotonin syndrome

Be careful when mixing Effexor with other medicines which also affect serotonin levels, such as other antidepressants, lithium and St. John’s Wort. This can lead to an excessive build-up of serotonin 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 chills
  • Muscle contractions
  • Unusual restlessness or restlessness

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

Risk of overdose

You should always avoid drinking or using other medicines while taking Effexor. These substances may decrease the benefit of the drug or lead to a toxic overdose. The most common effects of Effexor overdose include:

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

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

Suicidal thoughts and actions

Children and adolescents (up to 25 years of age) may have increased suicidal thoughts and behavior when taking antidepressants. The danger is greatest during the first months of treatment or when changing the dose.

While this warning holds true for all antidepressants, taking Effexor may further increase your risk. A major study found that Effexor was associated with a higher risk of successful suicide and attempted suicide compared to other antidepressants, including Celexa (citalopram), Prozac (fluoxetine), and Prothiaden (dothiepin).

Withdrawal syndrome

Suddenly stopping Effexor may cause one or more of the following withdrawal symptoms:

  • Anxiety or worsening depression
  • Dizziness
  • Gastrointestinal disturbances
  • Headache
  • Irritability
  • Nausea
  • Nightmares
  • Paresthesias (tingling, tingling sensation on the skin)
  • Vomiting

It is important that you do not stop taking Effexor on your own. If you and your doctor decide that it is best for you to stop Effexor, they may suggest a step-down strategy to minimize withdrawal symptoms.

A word from VigorTip

Before prescribing Effexor, your doctor will take a complete medical history. However, it is important that you take an active role in your care. Be sure to share every detail of your medical history whether or not you think it is important.

Overall, Effexor is a well-tolerated drug that has helped many people cope with a variety of mental health issues. You deserve to get well. The good news is, if Effexor isn’t helping you, there are plenty of other options to try.