A 12-month, Open-Label, Multicenter Extension Trial of Orally Administered Sodium Oxybate for the Treatment of Narcolepsy

Abstract

OBJECTIVES: To evaluate the long-term safety and efficacy of nightly sodium oxybate for the treatment of narcolepsy. DESIGN: A multicenter, 12-month, open-label trial. PARTICIPANTS: 118 narcolepsy patients previously enrolled in a 4-week double-blind sodium oxybate trial. INTERVENTIONS: Patients were administered 6 g sodium oxybate nightly, taken in equally divided doses at bedtime and 2.5 to 4 hours later. The study protocol permitted the dose to be increased or decreased in 1.5-g increments at 2-week intervals based on efficacy response or adverse experiences but staying within the range of 3 to 9 g nightly. MEASURES: Narcolepsy symptoms and adverse events were recorded in daily diaries. Safety measures included physical and laboratory examinations repeated at 6 and 12 months. The primary efficacy measure was the change in weekly cataplexy attacks from baseline. Secondary measures included daytime sleepiness using the Epworth Sleepiness Scale (ESS), inadvertent naps/sleep attacks, nighttime awakenings, and the overall change in disease severity as rated by the investigators (Clinical Global Impression of Change; CGI-c). RESULTS: Sodium oxybate, in doses of 3 to 9 g nightly, produced overall improvements in narcolepsy symptoms, which were significant at 4 weeks and maximal after 8 weeks. Reported improvements included a significant decrease in frequency of cataplexy attacks (p < 0.001); diminished daytime sleepiness (p < 0.001); and patient descriptions of nocturnal sleep quality, level of alertness, and ability to concentrate (for each p < 0.001). Adverse events were generally mild and patients showed no evidence of tolerance. CONCLUSION: Sodium oxybate is an effective and well-tolerated treatment for narcolepsy.