Long-term follow-up of patients with narcolepsy-cataplexy treated with sodium oxybate (Xyrem)

The clinical experience with sodium oxybate (Xyrem) in patients with narcolepsy-cataplexy is still limited, especially in children, elderly patients, and patients with concomitant obstructive sleep apnea (OSA). In this report, we describe 4 patients with narcolepsy and refractory cataplexy who were started on sodium oxybate and followed up for approximately 2 years, including an 11-year-old child and an elderly man with severe OSA.

The sodium oxybate dose was built up gradually until symptoms were controlled, adverse effects appeared, or the maximum nightly dose of 9.0 g was reached. On average, each subject underwent 4 sleep studies during follow-up after starting sodium oxybate. The nightly dose needed to control symptoms ranged from 5.0 to 9.0 g.

Cataplexy, sleep paralysis, and sleep-onset hallucinations disappeared in all cases. In addition, daytime sleepiness decreased subjectively according to the Epworth Sleepiness Scale and objectively according to the Multiple Sleep Latency Test. Polysomnography demonstrated clear reductions in sleep latency, arousal index, and stage 1 sleep (N1). Slow-wave sleep (N3) and sleep efficiency increased with sodium oxybate treatment. Interestingly, the 11-year-old child and the elderly man with documented severe OSA on continuous positive airway pressure therapy demonstrated tolerability to sodium oxybate. Adverse effects included nausea, snoring, paresthesia, convulsion, and enuresis. However, all adverse effects disappeared after reduction of the dose. The beneficial effect of sodium oxybate persisted during the follow-up period.

Sodium oxybate is an effective and well-tolerated medication for patients with refractory cataplexy. However, it requires special monitoring and follow-up by a specialized center. The improvement in clinical symptoms and sleep architecture seems to persist over time.