Effexor Side Effects

SNRI antidepressant, Effexor, may cause a number of side effects which can result in serious illness or injury. Severe Effexor side effects may include those affecting the cardiovascular and nervous system, the skin and musculoskeletal system, and may include birth defects when Effexor is taken during pregnancy.

Effexor is an antidepressant pharmaceutical medication used for treating major depressive disorder (MDD) and other mental problems. Effexor is also sometimes used to treat migraines and vasomotor instability, or hot flashes. Effexor side effects are very similar to side effects from SSRI, or selective serotonin reuptake inhibitor, medications. Effexor is slightly different from SSRI antidepressants because it is an SNRI, or serotonin norepinephrine reuptake inhibitor. However, Effexor side effects can be as dangerous as side effects from SSRIs.

Common Effexor Side Effects

Intended and unintended Effexor side effects are continuously recorded by the medical community in order to stay updated. This helps to keep patients safe from adverse complications. It is easier for doctors and other practitioners to treat patients when they can consider all potential problems.

Most common Effexor side effects:

  • headaches
  • dry mouth
  • nausea
  • increased perspiration

Other common Effexor side effects:

  • chills
  • confusion
  • dizziness
  • vision problems
  • increased tonicity (muscle tone)
  • anorgasmia
  • loss of appetite
  • pupil dilation
  • depersonalization
  • sexual problems
  • menstrual problems
  • sedation
  • urinary problems
  • paresthesia (tingling)

Less common Effexor side effects:

  • lower blood pressure
  • angioedema
  • muscle twitching
  • teeth grinding (bruxism)
  • weight gain
  • hair loss
  • apathy
  • skin rash
  • tinnitus
  • photosensitivity
  • gastrointestinal bleeding

Rare Effexor side effects:

  • convulsions
  • restlessness
  • mania
  • urinary incontinence

Effexor Side Effects on Bodily Systems

Nervous System

The common types of Effexor side effects are related to the central nervous system (CNS). Nervous system Effexor side effects include dizziness, somnolence, insomnia, fatigue, tremors, and abnormal dreaming. The prevalence of these effects is between 10 percent and 30 percent.

Effexor side effects can also be neutral (neither harmful nor beneficial). A unique Effexor side effect is that Effexor lowers sensitivity to pain in the sural nerve of the leg. Another unexpected Effexor side effect is the improvement of attention span, memory, concentration, and reaction time.

Sleep abnormalities can be caused by both SSRI and SNRI medications. Effexor has a dose-dependent effect on the rapid eye movement (REM) phase of sleep. Effexor can cause an overall reduction in REM sleep and increase REM onset latency (ROL). This side effect will rebound upon discontinuation of treatment but lack of REM sleep can result in long-term psychological problems.


At least 3 cases of Effexor side effects related alopecia have been recorded. Hair regrowth occurred 2 to 4 weeks following discontinuation. Effexor side effects can also cause eczema, acne, pruritis, urticaria, and hair discoloration. One case of Stevens-Johnson syndrome (toxic epidermal necrolysis) was also recorded.


Effexor side effects affecting the musculoskeletal system include rhabdomyolysis, myasthenia, rheumatoid arthritis, myopathy, and other conditions. These effects were recorded during Phase 3 experimental trials but official causality was never fully investigated.


Effexor side effects can cause hyperglycemia, hypercholesteremia, and hyperlipemia. These conditions refer to an excess of sugar, cholesterol, and fat in the blood. Effexor is also associated with statistically significant increases of both high density cholesterol (HDL) and low density cholesterol (LDL).

Hyponatremia, or low sodium in blood was frequently reported during clinical testing. There were at least 15 incidences of hyponatremia with at least one case that was life-threatening.


Several studies and reports have noted hypertension and tachycardia as Effexor side effects. Dose-related hypertension was seen from 3 percent and 7 percent increases at lower doses and 13 percent increase in higher doses.

Other cardiovascular Effexor side effects:

  • angina pectoris
  • bradycardia
  • arrhythmia
  • extrasystoles
  • hypotension
  • syncope
  • peripheral vascular disorder
  • thrombophlebitis
  • aortic aneurysm
  • hematoma
  • congestive heart failure
  • cerebral ischemia
  • coronary artery disease

Black Box Warning

Effexor was issued a black-box warning by the FDA because of an increased risk of suicide. Worsening of psychiatric condition and other unusual behavior were also noted. The demographic associated with the highest risk were patients being treated for MDD.

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