Effexor XR is the trade name for an extended release formulation of the drug venlafaxine. This medication is a member of the serotonin-norepinephrine reuptake inhibitor (SNRI) antidepressant drug group. Effexor is approved by the U.S. Food and Drug Administration (FDA) for the treatment of major depression, social anxiety disorder, generalized anxiety disorder and panic disorder. While generally safe and well tolerated, venlafaxine may cause physical and mental health problems in some who take this medication.
Increased Depression and Suicide Risk
A small percentage of people with major depression who are taking venlafaxine may experience worsening of their illness. This may be accompanied by new or intensified thoughts of suicide. In some cases, this has led to suicide attempts or completed suicides. The risk for these serious side effects of venlafaxine is greatest during the first one to two months of taking the drug and after a change in drug dose. Young adults age 18 through 24, adolescents and children are at greatest risk for these side effects.
The FDA has determined the increased risk of suicide is not unique to venlafaxine, but rather applies to all antidepressant medications. All carry an FDA-required black box warning regarding the potential for this serious side effect of prescription antidepressants.
Serotonin Syndrome
Venlafaxine increases the concentration of active serotonin in the brain. Serotonin is a neurotransmitter--a chemical that enhances or inhibits various brain-controlled functions. Venlafaxine may cause serotonin syndrome, a condition in which excessive serotonin causes physical symptoms including headache, confusion, hallucinations, agitation, loss of coordination, nausea, vomiting, diarrhea, shivering and excessive sweating. In severe cases, seizures, rapid heart rate and high fever may develop. Severe serotonin syndrome is potentially life threatening. The risk of serotonin syndrome is greatest when venlafaxine is taken with migraine medicines called triptans. If you are on venlafaxine, talk with your doctor before taking any prescription migraine medication to be sure it is safe for you.
Increased Blood Pressure
Venlafaxine may cause increased blood pressure. In a large research study published in the "Journal of Clinical Psychiatry," Dr. Michael Thase concluded venlafaxine causes significant increases in blood pressure, especially at doses of more than 300 milligrams per day. However, Dr. Thase added venlafaxine does not interfere with controlling pre-existing high blood pressure. If you are taking venlafaxine, be sure to have your blood pressure checked regularly.
Sexual Dysfunction
Sexual problems are a common side effect of venlafaxine and other SNRIs. Possible problems include decreased interest in sexual activity, delayed or absent orgasm in women, and delayed ejaculation and impotence in men. In a research article titled, "Prevalence of Sexual Dysfunction Among Newer Antidepressants" published in the "Journal of Clinical Psychiatry," lead author Dr. Anita Clayton reported more than one-third of people taking venlafaxine experience sexual dysfunction.
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