According to the Narcolepsy Network, although it affects more than 200,000 people in the US, narcolepsy is estimated to be undiagnosed or untreated in 75% of people with the disorder. This lack of recognition leads to delays in effective treatment and decreased quality of life. The US Food and Drug Administration has approved a variety of drugs to treat narcolepsy-associated excessive daytime sleepiness (EDS), including modafinil (Provigil), armodafinil (Nuvigil), methylphenidate, and amphetamine. Sodium oxybate (Xyrem) has been approved to treat the EDS and cataplexy associated with narcolepsy.
Sodium oxybate has been found to be effective for most people with narcolepsy who have taken the drug in clinical trials. However, patients must find the right dose of the drug that works for them (titration to efficacy) and must be able to tolerate the drug. Sodium oxybate does not work equally well for everyone, and there may be a lag from the time a person starts taking the drug until it becomes effective. Doctors and patients may find it helpful to know the average time that it takes for people to have a good response to this drug.
Who were the researchers and what did they do?
About 15 years ago, members of the Xyrem International Study Group conducted two studies in which they examined the effectiveness of sodium oxybate. In the first, they tested three different doses of the drug against placebo in 136 patients for four weeks. For the second study, all of the patients from the first study, whether they received sodium oxybate or placebo, were invited to take the drug for a minimum of an additional 12 months; 118 chose to take part in the second study.
Dr. Bogan and his colleagues recently looked at the data from these two studies to find out how long it took for sodium oxybate to effectively treat EDS and cataplexy in these patients with narcolepsy. They used two different definitions of response (one for EDS and one for cataplexy) to determine what percentage of patients responded to treatment and the time to effective treatment. The definition for EDS response was a 20% or greater improvement on the Epworth Sleepiness Scale score. The definition for cataplexy response was at least 50% fewer cataplexy attacks per week.
What were the results of the study?
Seventy-eight percent of the patients who took sodium oxybate for both studies were EDS responders, and 91% were cataplexy responders. The most common times to response were 37 days for EDS and 25 for cataplexy. The most common times tomaximum response were 106 days for EDS and 213 days for cataplexy. For those patients who initially took placebo and switched to sodium oxybate, the results were similar, except that time to maximum response was longer.
What were the authors’ conclusions?
Most patients’ symptoms responded to sodium oxybate within 2 months, but a longer period to reach maximum response was often needed. “Clinicians should recognize that time to initial and maximum response may take weeks to months.”
Bogan RK, Roth T, Schwartz J, Miloslavasky M. Time to response with sodium oxybate for the treatment of excessive daytime sleepiness (EDS) and cataplexy in patients with narcolepsy. J Clin Sleep Med. 2015 Jan 12. pii: jc-00353-14. [Epub ahead of print]