Forest Laboratories, Inc announced the results of a six-month study, which found that Lexapro (escitalopram oxalate) is as effective as Paxil (paroxetine hydrochloride) in patients with generalized anxiety disorder (GAD). When compared to Lexapro-treated patients, three times as many Paxil-treated patients withdrew from the study due to adverse events, and more than twice as many Paxil-treated patients experienced weight gain. Both Lexapro and Paxil belong to the class of antidepressants known as selective serotonin reuptake inhibitors (SSRIs). The findings were presented at the 24th annual meeting of the Anxiety Disorders Association of America (ADAA) in Miami.

"GAD is a chronic, debilitating disorder, and an SSRI is the treatment of choice for long-term therapy," said Robert Bielski, M.D., lead study investigator and former professor of Psychiatry at Michigan State University. "Lexapro was shown to be just as effective as Paxil in treating GAD but with a lower discontinuation rate due to adverse events."

Anxiety disorders are the most common mental illness in the United States, affecting more than 19 million adults and costing approximately $42 billion a year. Four million Americans, or 2.8 per cent of the adult population in the U.S., experience GAD; the disorder affects twice as many women as men. GAD is characterized by excessive anxiety and worry (apprehensive expectations) about daily events or activities for a period of six months or more. Other symptoms may include restlessness, irritability, difficulty concentrating, muscle tension, and sleep disturbance.

At the end of the six-month study, both Lexapro and Paxil were associated with improvement in anxiety symptoms. Mean changes in the Hamilton Rating Scale for Anxiety [HAM-A] scores from baseline to endpoint were -15.3 and -3.3, respectively. At endpoint, the overall mean daily doses of Lexapro and Paxil were 14.4 mg and 29.9 mg, respectively. Tolerability measures favored Lexapro over Paxil during the study. Significantly fewer Lexapro-treated patients withdrew from the study due to adverse events compared to patients treated with Paxil (6.6 per cent vs. 22.6 per cent, respectively). Lexapro-treated patients also had a lower incidence of clinically significant weight increase (greater than or equal to 7 per cent weight gain) (18 per cent vs. 8 per cent for Lexapro).

Of the adverse events reported by at least 20 per cent of patients in either treatment group, diarrhea (8 per cent vs. 21 per cent for Lexapro) was the only adverse event reported more frequently by Lexapro-treated patients. Adverse events that were reported numerically more frequently by Paxil-treated than Lexapro-treated patients included: sexual side effects, specifically ejaculation disorder (30 per cent vs. 15 per cent), anorgasmia (female orgasmic dysfunction) (26 per cent vs. 6 per cent), and decreased libido (23 per cent vs. 5 per cent), as well as insomnia (26 per cent vs. 15 per cent) and headache (21 per cent vs. 12 per cent), respectively.

One hundred twenty-three patients (18-65 years) with GAD HAM-A score greater than or equal to 18) participated in the randomized, double-blind, flexible-dose study. Following a one-week, single-blind, placebo lead-in period, patients were randomized, in a 1:1 ratio, to receive either 10 mg per day of Lexapro or 20 mg per day of Paxil. If clinically indicated, the Lexapro dose could be increased to 20 mg after four weeks of treatment, and the Paxil dose could be escalated in 10 mg increments at bi-weekly intervals to a maximum dose of 50 mg per day. The primary efficacy variable was the mean change from baseline to week 24 in the HAM-A total score.

Lexapro is the newest and fastest-growing selective serotonin reuptake inhibitor (SSRI) and has been prescribed for more than 4.5 million patients in the U.S.

Lexapro was approved by the U.S. Food and Drug Administration (FDA) in August 2002 for both the initial and maintenance treatment of major depressive disorder and in December 2003 for the treatment of generalized anxiety disorder. Lexapro is available as tablets and oral solution.

As with all SSRIs, Lexapro should not be taken with monoamine oxidase inhibitors (MAOI).

As with other psychotropic drugs that interfere with serotonin reuptake, patients should be cautioned regarding the risk of bleeding associated with the concomitant use of Lexapro with NSAIDs, aspirin, or other drugs that affect coagulation.

Forest Laboratories licenses Lexapro from H. Lundbeck A/S, the Danish pharmaceutical firm that developed escitalopram and citalopram.