NEW YORK (Reuters Health) – Patients with generalized anxiety disorder (GAD) are best treated with an antidepressant for at least 12 months, according to a study published in the December Archives of General Psychiatry.

Dr. Karl Rickels and colleagues from the Mood and Anxiety Disorders Section of the University of Pennsylvania School of Medicine say that even if patients with GAD want to go off their medication, they are likely to respond again to the same treatment.

According to the investigators, after 6 months of open-label venlafaxine XR, patients continuing the drug for 12 months experienced a statistically significant lower relapse rate than patients who switched to placebo (9.8% vs. 53.7%; P < 0.001).

Few studies have investigated long-term treatment outcomes in patients with GAD; “prior studies only treated patients for 3 to 6 months, not 12 months,” Dr. Rickels noted in an e-mail to Reuters Health.

The eighteen month “relapse prevention” study had three treatment phases, all utilizing venlafaxine hydrochloride extended release (XR): a 6-month, open-label venlafaxine XR, flexible-dose, treatment phase (75 to 225 mg per day) and two 6-month, randomized, double-blind, placebo-controlled relapse phases.

After 6 months, patients who improved were randomized to venlafaxine XR or placebo for 6 months. All venlafaxine XR patients still in the study at 12 months were randomized to receive venlafaxine XR or placebo, and all placebo patients continued to take placebo for another 6 months.

Of 268 patients with a diagnosis of GAD enrolled in open-label phase, 158 (59.0%) completed 6 months and 136 (50.7%) entered phase 2 (months 6 to 12). Fifty-nine (43.4%) of 136 patients entered phase 3 (months 12-18).

Patients treated with venlafaxine XR for 12 months before being shifted to placebo experienced a statistically significant lower relapse rate than patients shifted to placebo after being on the drug for only 6 months (32.4% vs. 53.7%; P < 0.03).

This study confirms that GAD is a chronic illness that “needs long-term treatment with an antidepressant anxiolytic of at least 12 months,” Dr. Rickels said.

“These preliminary additional findings are of clinical relevance for patients who for various reasons prefer not to be on a medication for longer than 6 months,” he and colleagues note in their report.

The study was supported by the US Public Health Service. Wyeth Pharmaceuticals, maker of venlafaxine, provided all study medication. Dr. Rickels and a colleague on the study disclose having received research support from Wyeth Pharmaceuticals.

Reference:
Time to Relapse After 6 and 12 Months’ Treatment of Generalized Anxiety Disorder With Venlafaxine Extended Release
Arch Gen Psychiatry 2010;67:1274-1281.