Narcolepsy type 2, or narcolepsy without cataplexy, shares all of the features of narcolepsy type 1 except cataplexy and low CSF orexin. Instances of abuse and dependence as well as withdrawal symptoms have been described, but are rare. Narcolepsy type 1, previously called narcolepsy with cataplexy, includes cataplexy as one of the earliest symptoms and is associated with low cerebrospinal fluid (CSF) orexin (also called hypocretin) levels. Uncommon, but potentially severe adverse reactions (usually associated with excessive doses) include hallucinations, mental confusion, abnormal thinking, disturbed sleep and depression. Common side effects include nausea, dizziness, headaches, mental confusion, paresthesia and enuresis (bed wetting). The recommended starting dose of both formulations of oxybate is 4.5 g at nighttime, which can be increased or decreased at two week intervals in increments of 1.5 g, not to exceed 9 g daily. In addition, a low-sodium formulation has been developed consisting of calcium, magnesium, potassium and sodium salts of oxybate and is available in a similar oral solution of 500 mg/mL under the brand name Xywav. Oxybate sodium is available as an oral solution in 180 mL bottles of 500 mg/mL under the brand name Xyrem. For these reasons, the availability of oxybate is restricted, and it can only be prescribed as a part of a risk evaluation and mitigation strategy (REMS) program. In addition, oxybate is a Schedule III agent, indicating that it has a mild-to-moderate potential for abuse and dependence. Although evaluated and reported to be partially beneficial in other conditions (fibromyalgia, chronic fatigue, alcohol abstinence), oxybate is not approved for these indications. These indications were broadened in 2005 to include improvement in the quality of nighttime sleep and decrease in daytime sleepiness in patients with narcolepsy. Oxybate was approved for use in the United States in 2002 as therapy for cataplexy in patients with narcolepsy. In prospective, randomized controlled trials, oxybate was effective in alleviating symptoms of daytime sleepiness and decreasing episodes of cataplexy in patients with narcolepsy.
Its mechanism of action is unclear, but it is a derivative of gamma-aminobutyric acid (GABA) and appears to be an agonist at the GABA-B receptor. Oxybate (ox' i bate) is a simple amino acid-like molecule (sodium 4-hydroxybutyrate) that has mild neuroactivity which acts to induce normal sleep patterns.
0 kommentar(er)
