Narcolepsy and effectiveness of gamma-hydroxybutyrate (GHB): a systematic review and meta-analysis of randomized controlled trials

Objectives: Gamma-hydroxybutyrate (GHB) is currently authorized by the European Medicines Agency (EMA) to treat narcolepsy with cataplexy in adults, and by the Food and Drug Administration (FDA) to treat cataplexy in patients with narcolepsy, with an expanded indication for the treatment of excessive daytime sleepiness. This study meta-analyses and reviews the effectiveness of GHB on the clinical features of narcolepsy and its neurophysiological correlates.

Methods: A systematic review of the literature using Medline, Embase, Web of Science, Cochrane reviews, clinical-trials.gov, Scopus, Scirus, and a subsequent meta-analysis were performed. Considered outcomes were: cataplexy attacks, subjective daytime sleepiness, sleep attacks, clinical global impression change (CGI-c), quality of life (QoL), hypnagogic hallucinations, sleep paralysis, mean sleep latencies on the multiple sleep latency test (MSLT) and maintenance of wakefulness test (MWT), nocturnal polysomnographic data.

Results: Nine randomized controlled trials reporting data on the effectiveness of GHB on narcolepsy were identified, for a total of 1,154 patients (771 patients in the GHB-treated group and 383 in the placebo group). The meta-analysis showed that GHB reduced cataplexy attacks both on a daily (weighted mean difference (WMD) -1.10; 95% confidence interval (CI) -1.29/-0.90, p < 0.00001) and a weekly basis (WMD -7.04; 95% CI -12.45/-1.63, p = 0.01), subjective nocturnal awakenings (WMD -1.33; 95% CI -1.78/-0.88, p < 0.00001), daytime sleep attacks on a weekly basis (WMD -9.30; 95% CI -15.92/-2.68, p = 0.006), subjective daytime sleepiness (WMD -2.81; 95% CI -4.13/-1.49, p < 0.0001) and sleep stage shifts (WMD -9.69; 95% CI -17.14/-2.24, p = 0.01). GHB increased sleep stages 3 + 4 (WMD 4.11; 95% CI 0.07/8.16, p = 0.05) and improved the CGI-c score (odds ratio (OR) 3.45; 95% CI 2.47/4.80, p < 0.00001). No significant changes were observed in night sleep latency, total sleep time, rapid-eye movement (REM) sleep and sleep stages 1 and 2.

Conclusions: This meta-analysis demonstrates the effectiveness of GHB in treating major, clinically relevant narcolepsy symptoms and sleep architecture abnormalities.