Wyeth announced that the U.S. Food and Drug Administration (FDA) approved Effexor XR (venlafaxine HCl) for the treatment of patients with social anxiety disorder (SAD), which may affect up to 13 per cent of Americans at some point in their lives.

Effexor XR, already approved for the treatment of depression and generalized anxiety disorder (GAD), is the first available serotonin-norepinephrine reuptake inhibitor (SNRI), and is believed to increase the levels of two key brain chemicals thought to be deficient in individuals suffering from depression and anxiety disorders. Effexor XR is the only SNRI approved for use in this broad range of mood disorders.

The FDA approved Effexor XR as treatment for SAD based on studies that demonstrate the drug's significant effectiveness as a short-term treatment for patients with SAD.

Effexor XR is a structurally novel antidepressant chemically unrelated to any other available antidepressant. Effexor XR is believed to increase levels of both serotonin and norepinephrine, two of the brain chemicals thought to be implicated in depression and anxiety disorders. Serotonin and norepinephrine are thought to regulate mood and may affect motivation and sense of well-being.

Effexor XR was discovered and developed by Wyeth Pharmaceuticals, the pharmaceutical division of Wyeth. The product is also marketed by Wyeth Pharmaceuticals. The immediate-release formulation was approved by the FDA in 1993; the extended-release (XR) formulation was approved in 1997. These medications are available only by prescription.

"Social anxiety disorder is a debilitating illness that can greatly disrupt an individual's daily life, yet the disorder is widely under treated," says Michael R. Liebowitz, M.D., professor of clinical psychiatry at Columbia University, director of the Anxiety Disorders Clinic at the New York State Psychiatric Institute, and lead investigator of one of the two pivotal Effexor XR SAD studies. "Now that Effexor XR is available for SAD, we have a different kind of treatment option to help alleviate the disabling symptoms of this illness."

Social anxiety disorder (SAD), also known as social phobia, is the third most common psychiatric disorder in the United States. SAD is a mood disorder marked by overwhelming and disabling fear of scrutiny, embarrassment, or humiliation in social situations, which are often avoided or else endured with dread. In particular, SAD patients have a 40 to 50 per cent lifetime prevalence of coexisting major depressive disorder.

"There are already abundant data supporting significant efficacy of Effexor XR in treating patients with depression and/or general anxiety disorder," said Victoria Kusiak, M.D., vice president of Global Medical Affairs and North American Medical Director of Wyeth Pharmaceuticals. "Now with the approval of the social anxiety disorder indication, its efficacy has been demonstrated across an even broader range of symptoms."

In two 12-week studies, Effexor XR significantly reduced patients' SAD symptoms compared to placebo as early as four or six weeks, with continued improvements through week 12. Scores were measured using the Liebowitz Social Anxiety Scale (LSAS).

In the first study, treated patients had significant reductions in average LSAS scores at week six (P <0.05), and even greater reductions occurred by week 12 (P <0.001).

In the second study, the significant reduction in average LSAS scores with EFFEXOR(r) XR occurred at the fourth week (P <0.01), and by week 12, the treated patients averaged even greater reductions compared to the placebo group (P <0.001).

None of the investigators or patients in either study (279 patients in the first and 272 patients in the second) knew whether the patients received Effexor XR or a placebo until the trials ended. The once-daily doses of Effexor XR ranged from 75 to 225 milligrams. Prior to the clinical trials, all participants received placebo for three to 10 days and after the trials, investigators tapered the patients' dosages for 14 days.

Treatment-related adverse events reported by patients included nausea, insomnia, anorexia, dry mouth, and sweating.

The most common adverse events reported in Effexor XR short-term placebo-controlled depression trials (incidence greater than or equal to 10% and greater than or equal to twice that of placebo) were nausea, dizziness, somnolence, delayed ejaculation, sweating, dry mouth, and nervousness; and in short-term generalized anxiety disorder (GAD) trials were nausea, dry mouth, abnormal ejaculation, constipation, and sweating.

Effexor XR is contraindicated in patients taking monoamine oxidase inhibitors (MAOIs). Treatment with venlafaxine is associated with sustained increases in blood pressure (BP) in some patients. Regular BP monitoring is recommended. Patients should not be abruptly discontinued from antidepressant medication, including Effexor XR; see the Dosage and Administration section of the Prescribing Information.