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Methylphenobarbital

Clinical data
Trade names	Mebaral, generics
AHFS/Drugs.com	International Drug Names
MedlinePlus	a605022
Routes of administration	By mouth (tablets)
ATC code	N03AA01 (WHO)
Legal status
Legal status	BR: Class B1 (Psychoactive drugs) CA: Schedule IV DE: Prescription only (Anlage III for higher doses) UK: Class B US: Schedule IV
Pharmacokinetic data
Protein binding	70–76%
Metabolism	Liver
Elimination half-life	34 hours
Identifiers
IUPAC name 5-Phenyl-5-ethyl-1-methylbarbituric acid
CAS Number	115-38-8
PubChem CID	8271
DrugBank	DB00849
ChemSpider	7972
UNII	5NC67NU76B
KEGG	D00700
ChEBI	CHEBI:6758
ChEMBL	ChEMBL45029
CompTox Dashboard (EPA)	DTXSID4023258
ECHA InfoCard	100.003.714
Chemical and physical data
Formula	C13H14N2O3
Molar mass	246.266 g·mol
3D model (JSmol)	Interactive image
SMILES O=C1N(C(=O)NC(=O)C1(c2ccccc2)CC)C
InChI InChI=1S/C13H14N2O3/c1-3-13(9-7-5-4-6-8-9)10(16)14-12(18)15(2)11(13)17/h4-8H,3H2,1-2H3,(H,14,16,18) Key:ALARQZQTBTVLJV-UHFFFAOYSA-N
(verify)

Methylphenobarbital (INN), also known as mephobarbital (USAN, JAN) and mephobarbitone (BAN), marketed under brand names such as Mebaral, Mephyltaletten, Phemiton, and Prominal, is a drug which is a barbiturate derivative and is used primarily as an anticonvulsant, but also as a sedative and anxiolytic. It is the N-methylated analogue of phenobarbital and has similar indications, therapeutic value, and tolerability.

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. The stated reason was because "the company thoroughly evaluated all avenues for keeping Mebaral available to patients, but ultimately concluded that no matter what steps they took, patients would be forced to transition to a new therapy."

The company further stated in a letter on its website that under the FDA's Unapproved Drugs Initiative, FDA is no longer willing to allow the drug to be grandfathered. A new drug application would have needed to have been submitted to gain marketing approval, which would have taken an estimated five years, during which time patients would be required to change their therapies in any case. The last available tablets bore an expiration date of March 31, 2012, and the drug will no longer be available in the US when supplies are depleted.

Side effects

The use of antiepileptic drugs including methylphenobarbital during pregnancy may be associated with birth defects.

Overdose

Symptoms of overdose of mephobarbital include confusion, decrease in or loss of reflexes, somnolence, fever, irritability, hypothermia, poor judgment, shortness of breath or slow/troubled breathing, slow heartbeat, slurred speech, staggering, trouble in sleeping, unusual movements of the eyes, weakness.

See also

• Hexobarbital
• Metharbital
• Phenobarbital

References

1. Anvisa (2023-03-31). "RDC Nº 784 - Listas de Substâncias Entorpecentes, Psicotrópicas, Precursoras e Outras sob Controle Especial" [Collegiate Board Resolution No. 784 - Lists of Narcotic, Psychotropic, Precursor, and Other Substances under Special Control] (in Brazilian Portuguese). Diário Oficial da União (published 2023-04-04). Archived from the original on 2023-08-03. Retrieved 2023-08-16.
2. Shorvon SD, Fish DR, Perucca E, Dodson WE, eds. (2004). The Treatment of Epilepsy (2nd ed.). Blackwell. ISBN 0-632-06046-8.
3. "Mebaral® (mephobarbital tablets, USP): Additional Product Discontinuation Information" (PDF). Lundbeck Inc. Archived from the original (PDF) on 10 August 2014.
4. Aksamija A, Habek D, Stanojević M, Ujević B (2009). "Fetal malformations associated with the use of methylphenobarbital and carbamazepine during pregnancy. Two case reports and review of the literature". Fetal Diagnosis and Therapy. 25 (1): 79–82. doi:10.1159/000201945. PMID 19218807.

• Anticonvulsants
• Barbiturates
• Methyl compounds
• Ethyl compounds
• Phenyl compounds