Effect of gaboxadol on patient-reported measures of sleep and waking function in patients with Primary Insomnia: results from two randomized, controlled, 3-month studies.

Objective: To evaluate the efficacy and safety of gaboxadol in the treatment of Primary Insomnia.

Methods: Two studies were performed in patients 18 to 65 years of age with Primary Insomnia. After a 7-day single-blind placebo run-in, patients were randomized to double-blind treatment with gaboxadol 15 mg (N = 310), 10 mg (N = 308), or placebo (N = 309) over 3 months in Study 1; and gaboxadol 15 mg (N = 304) or placebo (N = 301) over 12 months in Study 2. Treatment was administered at bedtime. The primary efficacy endpoints in each study were change from baseline in patient-reported total sleep time (sTST) and time to sleep onset (sTSO) at month 3. Safety was assessed primarily by adverse event reports.

Results: In Study 1, gaboxadol 15 mg significantly improved sTST (difference vs. placebo of 20.4 min, p < 0.01) and sTSO (difference vs. placebo of -9.8 min, p < 0.05) at 3 months, while gaboxadol 10 mg had no significant effects on these measures. In Study 2, gaboxadol 15 mg showed numerical superiority for improvements on sTST (difference vs. placebo of 14.5 min) and sTSO (difference vs. placebo of -4.9 min) at 3 months, but these differences were not significant. In both studies, there was evidence that the efficacy of gaboxadol was more pronounced in women than men. Gaboxadol was generally well tolerated over 3 months in Study 1, and over 12 months in Study 2.

Conclusion: Gaboxadol 15 mg showed variable efficacy on measures of sleep duration and onset at 3 months in adult patients with Primary Insomnia in these studies and appeared to be more effective in women than men. Gaboxadol 10 mg was not effective in these studies. (Clinical trial registration numbers: NCT00103818, NCT00095069).