A 2-week efficacy and safety study of gaboxadol and zolpidem using electronic diaries in primary insomnia outpatients

ObjectivesTo evaluate the efficacy and safety profile of gaboxadol, a selective extrasynaptic GABAA agonist (SEGA) previously in development for the treatment of insomnia.MethodsThis was a randomised, double-blind, placebo-controlled, parallel-group, 2-week, Phase III study of gaboxadol 5, 10 and 15 mg in outpatients meeting the DSM-IV criteria of primary insomnia (N = 742). Zolpidem 10 mg was used as active reference.ResultsAt weeks 1 and 2, significant improvement in total sleep time (sTST) compared to placebo was seen for all doses of gaboxadol (all p < 0.05). In addition, gaboxadol 10 and 15 mg decreased the number of awakenings (sNAW) (p < 0.05) while only gaboxadol 15 mg improved wakefulness after sleep onset (sWASO) (p < 0.05). At week 1, all doses of gaboxadol significantly improved time-to-sleep onset (sTSO) (p < 0.05). At week 2, a sustained effect on sTSO was observed for gaboxadol 15 mg. Zolpidem also showed effect on all of these variables. Gaboxadol and zolpidem improved sleep quality, freshness after sleep, daytime function and energy at both weeks. Transient rebound insomnia was observed following discontinuation of treatment with zolpidem, but not gaboxadol.ConclusionsGaboxadol 15 mg treatment for 2 weeks significantly improved sleep onset and maintenance variables as well as sleep quality and daytime function, as did zolpidem. Gaboxadol 5 and 10 mg also showed benefits on most efficacy variables. Gaboxadol was generally safe and well tolerated, with no evidence of withdrawal symptoms or rebound insomnia after discontinuation of short-term treatment. For zolpidem, transient rebound insomnia was observed.