Sunday, December 11, 2005

Reader Question about Xyrem

A reader (Dozy) asks: Can you talk a bit to how Xyrem is supposed to work? My understanding is it's entirely out of your system in 12 hours after taking it, so how would it help with Cataplexy for the other 12 hours? Xyrem is the only FDA approved treatment for Cataplexy, and has been approved recently for EDS as well. It is the only proven non-stimulant EDS medicine that I'm aware of for the treatment of EDS. For those PWN who have anxiety issues (like me), a non-stimulant approach is vital to functioning. Do you know if other non-stimulant meds are on the horizon?
As far as non-stimulants on the horizon, in 2006 a new version of Provigil, called Nuvigil, that contains only 1 of the 2 isomers (mirror images) of the molecule should be coming out. I think that researchers are also working on treatments that involve hypocretin.
No one is exactly sure how xyrem has its therapeutic effect in narcolepsy. It probably improves sleepiness in narcolepsy by consolidating nocturnal sleep and increasing slow wave sleep. It acts on multiple neurochemical systems. According to Principles and Practice of Sleep Medicine "Most studies to date indicate that the sedative-hypnotic effect is mediated through GABA-B agonist activity". It is also thought to act on the poorly understoon GHB receptor.
I don't know why it has an effect on cataplexy even after it is out of the blood stream- I can only guess that there is still some left in the brain or that it is having some long-lasting effect in the brain. Sorry I can't fully answer your question about xyrem (also known as sodium oxybate and gamma-hydroxybutyric acid)


: Joseph j7uy5 said...

You may be right. If I recall corrctly (and it is too late for me to try to find links) there are at least some drugs that persist in the brain far longer than what is reflected in the blood. The half-life that is reported for a drug is that which is determined by blood samples. What is important, though, is how much is in the brain.

yawningdog said...

The symptoms of narcolepsy like cataplexy, and excessive daytime sleepiness, are caused by a lack of deep restorative sleep.

So, it is not so much that xyrem is fixing cataplexy. It is the deep sleep that a narcoleptic gets with xyrem that is improving the narcoleptic symptoms including cataplexy.

Stephen said...

Dr. Rack -
Xyrem is not FDA approved for pediatric use
- would you consider using it in an older adolescent?