Excessive Daytime Sleepiness (EDS)
Until relatively recently EDS was only treated with amphetamine-like central nervous system (CNS) stimulants. The compound most commonly used in the UK is dexamphetamine sulphate (dexamfetamine sulphate, Dexedrine). Other possibilities are methylphenidate (Ritalin), the most commonly used drug in the USA, and mazindol (Teronac). Unlike, dexamphetamine, neither of these latter two medications are licensed for the treatment of narcolepsy.
Please note that, at present (November 2008), mazindol is no longer available in the UK. As soon as the situation changes further news will be posted on this page.
In 1998 a drug of quite a different type was introduced into the UK and is available on prescription. This is modafinil, marketed under the name Provigil. This drug works in a different way to the CNS stimulants and is regarded as a wake-promoter.
Recently a new drug, sodium oxybate (Zyrem), has been introduced to treat EDS. This drug is interesting as it is also licensed to treat cataplexy - another important symptom of narcolepsy. Unlike previous drugs used to treat narcolepsy sodium oxybate does not appear to be a stimulant of the CNS nor a wake promoter. Its mechanism of action is, at present, unknown although it may be related to an improvement in the quality of night-time sleep which results from taking this drug. This medicine is taken at night, often in divided doses.
Some doctors may treat EDS with a combination of two or more of the drugs discussed above.
Other potential treatments are currently being studied. Drugs which mimic the effects of hypocretins (orexins) are being developed which may eventually be used clinically. Another line of research involves drugs called histamine H3 antagonists. These agents increase the amount of histamine released from nerve endings in certain parts of the brain. Histamine produces arousal and so the H3 antagonists might be expected to be of use in the treatment of EDS associated with narcolepsy.
Intravenous immunoglobulin has been shown, in preliminary studies, to reduce the symptoms of narcolepsy, particularly when given soon after the first symptoms have developed. Furthermore, in a narcoleptic subject with low CSF hypocretin the administration of immunoglobulin resulted in a normalisation of hypocretin concentrations. Immunotherapy may prove to be a useful form of treatment in the future.
Before taking any prescribed medication it is very important that patients read the Patient Information Leaflet packed with the medication. This summarises, in lay people's language, information relating to the efficacy and safety of the medicine. It will also list the side effects which have been observed in patients taking the drug. Patients should avoid stopping treatment without discussion with their doctor or pharmacist.
For more detailed information on these drugs see the Narcolepsy association's booklet "Narcolepsy - a patient's guide to treatment". Click here to download an application form to purchase this booklet.
Note: pregnant or nursing mothers should discuss with their doctor the advisability of taking these drugs .