Effexor (venlafaxine) is a serotonin-norepinephrine reuptake inhibitor (SNRI) antidepressant. It is used to treat depression and anxiety disorders and though it is similar to SSRIs, some of Effexor’s side effects may be different.

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Quick Summary


Effexor (venlafaxine hydrochloride) is a serotonin-norepinephrine reuptake inhibitor (SNRI) antidepressant drug approved for the treatment of major depression. A controlled release form, Effexor XR is also approved treat generalized anxiety, panic disorder, and social phobia. SNRIs work by regulating serotonin and norepinephrine reabsorption.

Effexor was approved by the FDA in 1993 and was the first antidepressant of the SNRI category and was intended to be more effective with fewer side effects than SSRI medications.

Effexor Side Effects

Effexor may cause common side effects including nausea, changes in sex drive, insomnia or nervousness, drowsiness or dizziness, blurred vision, headache, weight and appetite changes, sweating and blurred vision.

It may also cause more severe side effects or complications which may be serious or life threatening such as:

  • Birth Defects – increased risk of birth defects may include miscarriage, heart and lung defects, persistent pulmonary hypertension of the neonatal (PPHN), and brain, skeletal or abdominal malformations such as anencephaly, craniosynostosis or omphalocele.
  • Serotonin Syndrome – caused by an buildup of serotonin in areas of the brain which may be severe or life-threatening. Symptoms include severe nausea or vomiting, changes in mental function, blood pressure, heart rate, muscular symptoms, and sudden or severe fever.
  • Withdrawal or Discontinuation Syndrome – sudden discontinuation may cause symptoms such as loss of coordination, stomach cramps, sever headache, sleepiness, or odd sensations. When possible, Effexor should be slowly tapered over a period of time.

Severe side effects should be reported to a medical professional and may require emergency treatment.

Effexor Overview

Effexor (venlafaxine hydrochloride) is a serotonin-norepinephrine reuptake inhibitor (SNRI) antidepressant drug approved to treat depression. A controlled release form, Effexor XR is used to treat conditions such as anxiety, panic disorders, and social phobia. SNRIs regulate serotonin and norepinephrine reabsorption and while some patients taking Effexor experience few side effects, others struggle with serious side effects and complications.

Effexor was approved by the FDA in 1993 and was the first antidepressant of the SNRI category. By 2007, Effexor became the sixth most popularly-prescribed drug of its class with more than 17 million prescriptions in the United States.

In 2007, Effexor’s manufacturer, Wyeth was given a warning by the U.S. Food and Drug Administration (FDA) regarding misleading advertising which had minimized the risks of Effexor and overstated the effectiveness. Wyeth was acquired by Pfizer in 2009 and now manufactures Effexor XR and similar medications.

Serotonin-Norepinephrine Reuptake Inhibitor (SNRI) Antidepressants

Effexor is slightly different from SSRI antidepressants because it is an SNRI, or serotonin norepinephrine reuptake inhibitor and while many people may experience fewer side effects, they may still be bothersome or serious. Other members of the SNRI class of medications include Cymbalta (duloxetine), Pristiq (desvenlafaxine) and Savella (milnacipran). SNRIs work to treat depression and other mental disorders by increasing the activity of neurotransmitters or chemical messengers, serotonin and norepinephrine, in certain areas of the brain.

Effexor (as generic venlafaxine) and Effexor XR is approved to treat major depression which has symptoms such as:

  • Loss of interest in normal activities
  • Feelings of guilt or worthlessness
  • Excessive crying
  • Lack of energy
  • Loss of concentration
  • Changes in appetite
  • Changes in sleep patterns
  • Suicidal thoughts and tendencies

Effexor as a “fast-release” medication is no longer manufactured by Pfizer but may still be available generically and requires multiple doses to be taken each day. Once-daily Effexor XR is also approved to treat generalized anxiety disorder, social anxiety disorder and panic disorder. As an off-label medication, Effexor has been used to treat pain caused by severe migraines, diabetic neuropathy and hot flashes.

Federal law allows for medications to be prescribed for non-approved conditions, but pharmaceutical companies are prohibited from marketing medication for those reasons.

Effexor Birth Defects

Effexor use has been associated with a number of birth defects when the drug is taken during pregnancy. The FDA has given venlafaxine a pregnancy category of C which indicates that Effexor has caused harm to animals during testing but has not been fully tested in humans.

The Canadian Medical Association Journal published a study in 2010 on venlafaxine, the active ingredient in Effexor. The study indicated that the risk of miscarriage was double in women who took the drug during pregnancy.

Effexor birth defects include:

  • Persistent pulmonary hypertension of the newborn, or PPHN
  • Respiratory distress
  • Heart defects and malformations
  • Physical defects such as cleft lip and palate
  • Anencephaly, or the absence of parts of the brain and skull
  • Craniosynostosis, which causes abnormal skull and brain growth
  • Omphalocele, or an abdominal defect that causes organs to protrude from the belly button

Pregnant or nursing mothers face serious risks. Effexor carries the potential risk of birth defects in some pregnancies. After birth, nursing infants may still develop side effects related to Effexor use from their mothers.

Newborns may develop symptoms such as:

  • Irregular appetite or difficulties feeding
  • Heart defects
  • Growth or development defects
  • Jitteriness or shaking
  • Seizures
  • Consistent or abnormally frequent crying

Effexor Side Effects

As with any medication, patients may experience some side effects when taking Effexor. Some occur often are mild-to-moderate, but others may be serious.

Common Effexor side effects may include:

  • Dry mouth
  • Dizziness
  • Nausea
  • Headache
  • Blurred vision
  • Increased sweating
  • Nervousness or insomnia
  • Drowsiness or fatigue
  • Constipation
  • Strange dreams
  • Appetite and weight change
  • Decreased libido, sex drive, and difficulty achieving orgasm

Bothersome or persistent side effects should be reported to a medical professional.

Severe Effexor side effects may include:

  • Trouble breathing or tightness in the chest
  • Memory
  • Hallucination
  • Seizures
  • Fever, nausea, or vomiting
  • Increased heart rate or blood pressure
  • Hostility, agitation, aggression
  • Suicidal thoughts or behavior
  • Sudden changes in moods or behavior
  • Anxiety or panic attacks

Severe or sudden side effects should be reported to a health care professional right away.

Effexor Serotonin Syndrome

Though it most commonly occurs in SSRI-type antidepressants, SNRI medications such as Effexor may also result in excessive serotonin buildup in the brain.

Symptoms may include:

  • Sudden spikes in blood pressure or heart rate
  • Higher than normal body temperature
  • Unexpected muscle contractions
  • Changes in mental status
  • Loss of consciousness

Symptoms of serotonin syndrome should be treated as an emergency.

Effexor Withdrawal or Discontinuation Syndrome

Experts recommend that patients consult a physician before stopping Effexor use. Stopping too soon can lead to discontinuation syndrome.

Effexor withdrawal symptoms:

  • loss of coordination
  • stomach cramps
  • severe headaches/migraines
  • extreme sleepiness
  • fatigue

Effexor Lawsuits

After its acquisition of Wyeth, Pfizer assumed responsibility for Effexor liability including lawsuits filed due to medical injury. Pfizer has faced multiple lawsuits after Effexor was used during pregnancy and may have caused birth defects. Women have said that they would not have used Effexor during pregnancy if they had been properly warned of the risk. The company may also have faced lawsuits for other side effects or medical injuries. People or loved ones of those who experienced harm due to Effexor, should seek legal assistance.

Notwithstanding claims relating to this product, the drug/medical device remains approved by the U.S. FDA.