Sodium oxybate

Sodium oxybate

Systematic (IUPAC) name
Sodium 4-hydroxybutanoate
Clinical data
Trade names	Xyrem, Alcover
AHFS/Drugs.com	monograph
MedlinePlus	a605032
Licence data	EMA:Link, US FDA:link
Pregnancy cat.	B (US)
Legal status	CDSA Schedule III/FDA Schedule G Part I (CA) CD (Benz) POM (UK) Schedule III (US) Rx Only
Routes	Oral
Pharmacokinetic data
Bioavailability	25%
Protein binding	1%
Half-life	0.5 to 1 hour.
Excretion	Almost entirely by biotransformation to carbon dioxide, which is then eliminated by expiration
Identifiers
CAS number	502-85-2 N
ATC code	N07XX04
PubChem	CID 23663870
ChemSpider	9983 Y
UNII	7G33012534 Y
KEGG	D05866 Y
ChEMBL	CHEMBL1200682 N
Chemical data
Formula	C4H7NaO3
Mol. mass	126.09 g/mol
SMILES [Na+].[O-]C(=O)CCCO
InChI InChI=1S/C4H8O3.Na/c5-3-1-2-4(6)7;/h5H,1-3H2,(H,6,7);/q;+1/p-1 Y Key:XYGBKMMCQDZQOZ-UHFFFAOYSA-M Y
N (what is this?)  (verify)

Sodium oxybate (INN; tradenames Xyrem and Alcover) is a prescription medication approved by the U.S. Food and Drug Administration (FDA) for the treatment of excessive daytime sleepiness (EDS) associated with narcolepsy,^[1] and by the FDA and Health Canada for the treatment of cataplexy associated with narcolepsy.^[2][3] Sodium oxybate is the sodium salt of γ-hydroxybutyric acid (GHB). Xyrem is manufactured by Jazz Pharmaceuticals in the US and Valeant Pharmaceuticals in Canada. Under the name Alcover, it is used in Italy for treatment of alcohol withdrawal and dependence.^[4]

Development

Alcover sold in Italy for therapeutic use.

Sodium oxybate is designated as an orphan drug, a pharmaceutical drug developed specifically to treat an orphan disease.^[5] The development of sodium oxybate oral solution as a prescription medication was initiated by the Office of Orphan Products Development (OOPD),^[6] a department of the FDA dedicated to promoting the development of products that demonstrate promise for the diagnosis and/or treatment of rare diseases or conditions.^[7]

• In 1994, the OOPD petitioned a pharmaceutical company called Orphan Medical to investigate sodium oxybate as a potential treatment for narcolepsy.^[6]
• In 1996, Orphan Medical submitted an Investigational New Drug Application (IND) to the FDA and began Phase I, II, and III clinical trials to investigate the safety and efficacy of sodium oxybate.^[6]
• In 2000, Orphan Medical submitted a New Drug Application (NDA) to the FDA for sodium oxybate.^[6] Sodium oxybate was granted "Priority Review",^[6] which is an expedited review process given to products that offer a major advance in treatment or treatment where no adequate therapy exists.^[8]
• In 2002, sodium oxybate received approval from the FDA for the treatment of cataplexy in patients with narcolepsy.^[2]
• In 2005, the Xyrem brand was acquired by Jazz Pharmaceuticals when they purchased Orphan Medical. Later that year, sodium oxybate was granted a second indication by the FDA for the treatment of EDS in patients with narcolepsy.^[1] Also that year sodium oxybate was approved for the treatment of cataplexy in patients with narcolepsy by Health Canada's Therapeutic Products Directorate,^[3] and for the same indication in adult patients by the European Medicines Agency for the European Union (EU) and the Swiss Agency for Therapeutic Products, Swissmedic.^[9]
• In 2006, sodium oxybate received an expanded indication for narcolepsy with cataplexy in the EU.^[9]
• In 2010, Jazz Pharmaceuticals completed two Phase III clinical trials investigating sodium oxybate for the treatment of fibromyalgia. Fibromyalgia is a complex musculoskeletal disorder clinically characterized by widespread pain usually accompanied by fatigue, insomnia, and dyscognition. The company submitted a New Drug Application (NDA) to the FDA; approval was refused in October.^[10]

There are also ongoing tests to see if sodium oxybate could prove helpful with other medical conditions, such as Parkinson's disease, chronic fatigue syndrome (ME), schizophrenia,^[11] binge eating,^[12] essential tremor and other non-Parkinson's movement disorders,^[13] and chronic cluster headache.^[14]

Mechanism of action

According to the U.S. Food and Drug Administration, the precise mechanism of action for the prescription medication sodium oxybate is unknown.^[15]

However, the active metabolite of Sodium Oxybate, gamma-Hydroxybutyric acid, is known to produce its therapeutic effects by agonizing the GABA_B receptor complex and the GHB receptor. This likely contributes to some part of Sodium Oxybate's therapeutic effects.

Cost

Orphan drugs by their nature are very specialized and have relatively few patients to spread the costs associated with bringing them to market. The average cost of a specialty drug in the US was $65,000 annually in June of 2013 (about $5,416 a month). The price of Xyrem in the US has inflated by an average of 40% annually since it became available as a prescription. "Jazz’s high prices on Xyrem has been successful due to the willingness of insurance companies to reimburse the cost of Xyrem, Despite the high costs of Xyrem, nearly every patient gets the drug pretty cheaply — Jazz subsidizes all co-payments above $35 per month — so few users care what Jazz charges., ^[16]

In European Union (EU) countries, the government either provides national health insurance (as in the UK and Italy) or strictly regulates quasi-private social insurance funds (as in Germany, France, and the Netherlands). These government agencies are the sole purchaser (or regulator) of medical goods and services and have the power to set prices.^[17] The cost of pharmaceuticals, including sodium oxybate, tends to be lower in these countries.^[17]

In the US, the cost of Xyrem is $3,085.60 per 180 mL bottle (500 mg/mL), compared to $576.00 (£360) in the UK under the NHS.^{[citation needed]} The effective dose range is 4.5–9 grams per night, which equates to $4,628.40 (4.5g) to $9,256.80 (9g) per month as of October 2013; Jazz Pharmaceuticals increases its prices for Xyrem on a semi-annual basis. Xyrem is covered by most insurance plans including Medicare and Medicaid and approximately 90% of Xyrem patients have a flat monthly co-pay. 75% of Xyrem insurance copays are less than $50 and 42% are less than $25 for a one-month supply. The manufacturer offers a coupon program for patients with larger co-pays. Some insurance companies may require physicians to fill out an insurance form called a Prior Authorization as part of the prescribing process. Additionally, the manufacturer offers a Patient Assistance Program to patients that do not have insurance and are unable to afford their Xyrem prescription. Approximately 8% of Xyrem patients currently participate in this program and receive their prescription for free.^[18]

Existing US Patents on sodium oxybate prevent other companies from manufacturing it as a drug. Sodium oxybate is protected by US Patents 6472431,^[19] and 6780889^[20] In total, sodium oxybate is protected by eight patents related to the product's formulation and Jazz Pharmaceuticals' distribution system. These patents expire from 2019 to 2024.^[21]

Distribution

A number of measures have been put in place by sodium oxybate's manufacturers to ensure that it is used safely and appropriately. For example, in the US sodium oxybate requires a prescription and can only be obtained through a restricted distribution program, called the "Xyrem Success Program". This restricted distribution program is required by the FDA as part of a Risk Management Program (RMP) to manage product safety and prevent abuse.^[22]

The program involves many risk management components, such as:

• Physician education
• Registration
• Patient education
• Detailed patient surveillance

The program includes a single centralized pharmacy with a toll-free number.

Initial dosages are set by the prescribing physician. Each bottle of sodium oxybate is shipped with a graduated syringe (measured in grams) and two dosing cups. Each night, the patient mixes two doses with 60 ml of water (sometimes substituted with a calorie-free beverage to cover the unpleasant taste of the medication). The first dose is taken at bedtime, and the second is taken 2.5 to 4 hours later.

Safety

The American Academy of Sleep Medicine (AASM) recommends sodium oxybate as a standard of care for the treatment of cataplexy, daytime sleepiness, and disrupted sleep due to narcolepsy in its Practice Parameters for the Treatment of Narcolepsy and other Hypersomnias of Central Origin,^[23] and the drug has been safely used by patients with narcolepsy for more than seven years.^[9] A recent analysis evaluated the postmarketing safety of sodium oxybate (Wang et al. 2009), including rates of abuse, dependence, and withdrawal, using a conservative application of the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV) criteria to all worldwide sodium oxybate adverse event cases containing reporting terminology related to abuse or misuse.^[9] The analysis included cases reported to the manufacture from market introduction in 2002 through March 2008. Using the DSM-IV criteria, the analysis found the following rates of abuse, dependence, and withdrawal of the approximately 26,000 patients who used sodium oxybate during this period:

• Abuse – 10 cases (0.04%)
• Dependence – 4 cases (0.016%)
• Withdrawal symptoms after discontinuation – 8 cases (0.031%; including 3 of the previous 4 dependence cases)

The analysis also found 2 confirmed cases (0.008%) of sodium oxybate–facilitated sexual assault; in both cases the women knew that they were taking sodium oxybate. In addition, there were 21 deaths (0.08%) in patients receiving sodium oxybate treatment, with 1 death known to be related to sodium oxybate, and 3 cases (0.01%) of traffic accidents involving drivers taking sodium oxybate. The extremely low rates of abuse, dependence, withdrawal, and assault found in this analysis suggest that after seven years of commercial availability, sodium oxybate use is largely appropriate and confined to patients with legitimate therapeutic needs.^[9]

In the US, sodium oxybate is classified as a Schedule III controlled substance for medicinal use under the Controlled Substances Act, with illicit use subject to Schedule I penalties. Examples of other schedule III products in the US include Vicodin, Tylenol with codeine, and testosterone.^[24] In Canada and the European Union (EU), it is classified as a Schedule III and a Schedule IV controlled substance, respectively.^[9] Sodium oxybate is the only treatment for narcolepsy approved by the World Anti-Doping Agency, and has been instrumental in allowing cyclist Franck Bouyer to resume his career.^[25]

On October 18, 2011, Jazz Pharmaceuticals, Inc. disclosed that it had received a Warning Letter from the FDA for specific violations during the FDA's inspection of the firm from April 27, 2011 through May 6, 2011.^[26] In the letter the FDA cited 2 specific violations: 1. Failure to develop adequate written procedures for the surveillance, receipt, evaluation, and reporting of postmarketing adverse drug experiences to FDA [21 C.F.R § 314.80(b)]. 2. Failure to submit adverse drug experience (ADE) reports that are both serious and unexpected to FDA within 15 calendar days of initial receipt of the information by the applicant [21 C.F.R. § 314.80(c)(1)(i)]. The firm also received an FDA form 483 on September 27, 2007, for similar post-marketing safety violations.^[26]

Adverse effects

Sodium oxybate is generally well tolerated by most patients. The most common side effects reported in clinical trials include nausea, dizziness, headache, vomiting, sleepiness, and bed-wetting.^[27][28] Some patients treated with sodium oxybate have also experienced moderate to significant weight loss. This may be due to the fact that sodium oxybate improves sleep architecture and increases the length of deep sleep stages, resulting in increased production of human growth hormone (HGH) and changes in energy metabolism.^[29] The weight loss could also be due to decreased daytime appetite (experienced by many users) and the instructions to not eat for two hours before bedtime. Serious side effects, as listed on all prescriptions of sodium oxybate, can include hallucinations, agitation, severe mental confusion, abnormal thinking, disrupted sleep, and depression.

See also

• Narcolepsy
• Cataplexy
• Excessive daytime sleepiness
• Alcohol withdrawal syndrome

References

Further reading

• Laborit, H (1964). "Sodium 4-hydroxybutyrate". Neuropharmacology 3 (4): 433–51. doi:10.1016/0028-3908(64)90074-7. PMID 14334876. 
• Neuman, Ariel (Apr 2004). GHB's Path to Legitimacy: An Administrative and Legislative History of Xyrem. Harvard Law. 

External links

• Xyrem Official Website Jazz Pharmaceuticals
• Xyrem Package Insert
• WebMD – Xyrem