Mephobarbital is a barbiturate derivative used primary as an anticonvulsant, but also as a sedative and anxiolytic. Marketing of mephobarbital was discontinued in 2012.

Mephobarbital:
https://drugs.ncats.io/drug/5NC67NU76B

A barbiturate that is metabolized to phenobarbital:
Methylphenobarbital, also known as mebaral or mephobarbitone, belongs to the class of organic compounds known as barbituric acid derivatives. Barbituric acid derivatives are compounds containing a perhydropyrimidine ring substituted at C-2, -4 and -6 by oxo groups. Methylphenobarbital binds at a distinct binding site associated with a Cl- ionopore at the GABAA receptor, increasing the duration of time for which the Cl- ionopore is open. Methylphenobarbital is a drug which is used for the relief of anxiety, tension, and apprehension, also used as an anticonvulsant for the treatment of epilepsy. Barbiturates act as nonselective depressants of the central nervous system (CNS), capable of producing all levels of CNS mood alteration from excitation to mild sedation, hypnosis, and deep coma. Methylphenobarbital is a very weakly acidic compound (based on its pKa). Methylphenobarbital is a potentially toxic compound. Methylphenobarbital is only found in individuals that have used or taken this drug. It has been used for similar purposes, especially in epilepsy, but there is no evidence Methylphenobarbital offers any advantage over phenobarbital. About 75% of a single oral dose of Methylphenobarbital is metabolized to phenobarbital in 24 hours.

Metabocard for Methylphenobarbital:
https://hmdb.ca/metabolites/HMDB0014987

Letter from Lundbeck to prescribers:
Mebaral became available for use in this country in 1935 before the New Drug Application (NDA) process was implemented via the 1962 amendments to the Federal Food, Drug and Cosmetic Act. In 2010, Lundbeck learned that a New Drug Application (NDA) would be required to continue making Mebaral available. There were a number of factors that made it impossible for the company to secure regulatory approval in a timeframe that would enable patients to continue on the therapy without disruption. Gathering sufficient evidence to support an NDA submission and gain FDA approval is a complex process which in this situation would take at least 5 years to complete, and would force those on Mebaral to transition to another therapy despite the company's best efforts.

Lundbeck is aware of the difficult situation that some patients may face with regard to the discontinuation of Mebaral. The company thoroughly evaluated all avenues for keeping Mebaral available to patients, but ultimately concluded that no matter what steps we took, patients would be forced to transition to a new therapy.

Lundbeck's remaining Mebaral inventory has a March 2012 expiration date, and we are no longer able to support product deliveries.

Mebaral (mephobarbital tablets, USP) Additional Product Discontinuation Information (PDF 1 page):
https://www.lundbeck.com/upload/us/files/pdf/Products/Mebaral_Discontinuation_Information_US_Website_FINAL%20_2_.pdf

Alternate Names:
Prominal, Methylphenobarbital, Methylphenobarbitone, Mephobarbital, Enphenemal, Menta-Bal, Mebaral, Phenmiton, Phemitone, Phemiton, Mephyltaletten, 115-38-8, N-Methylphenobarbital, Metilfenobarbitale, Mephobarbitone, 5-Ethyl-1-methyl-5-phenylbarbituric acid

Mephobarbital Drug Record:
http://www.dgidb.org/drugs/MEPHOBARBITAL#_summary

Methyl phenobarbital Safety Data Sheet (PDF 7 pages):
https://fagron.com/sites/default/files/document/msds_coa/115-38-8_(GB).pdf

Approval History:
1935 - Mebaral was introduced by Winthrop Pharmaceuticals.
2001 - Methylphenobarbital discontinued in the UK.
2003 - Mebaral was acquired by Ovation Pharmaceuticals (a specialty pharmaceutical company that acquired under-promoted branded pharmaceutical products).
2009 - Ovation was acquired by Lundbeck, which now markets Mebaral.
2012 - Lundbeck announced that they were abandoning the product in the US as of January 6, 2012