Methohexital or methohexitone (marketed under the brand names Brevital and Brietal) is a drug which is a barbiturate derivative. It is classified as short-acting, and has a rapid onset of action.^[2] It is similar in its effects to sodium thiopental, a drug with which it competed in the market for anesthetics.

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Quick Facts Clinical data, Trade names ...

Methohexital

Clinical data
Trade names	Brevital Sodium
Other names	Methohexitone
AHFS/Drugs.com	Consumer Drug Information
License data	US DailyMed: Methohexital
Routes of administration	Intravenous, rectal
Drug class	Barbiturate
ATC code	N01AF01 (WHO) N05CA15 (WHO)
Legal status
Legal status	AU: S4 (Prescription only) US: Schedule IV[1]
Pharmacokinetic data
Bioavailability	I.V. ~100% Rectal ~17%
Metabolism	Liver
Elimination half-life	5.6 ± 2.7 minutes
Excretion	excreted in feces
Identifiers
IUPAC name 5-Hex-3-yn-2-yl-1-methyl-5-prop-2-enyl-1,3-diazinane-2,4,6-trione
CAS Number	151-83-7 Y
PubChem CID	9034
IUPHAR/BPS	7233
DrugBank	DB00474 Y
ChemSpider	8683 Y
UNII	E5B8ND5IPE
KEGG	D04985 Y
ChEBI	CHEBI:102216 Y
ChEMBL	ChEMBL7413 Y
CompTox Dashboard (EPA)	DTXSID1023287
ECHA InfoCard	100.005.272
Chemical and physical data
Formula	C14H18N2O3
Molar mass	262.309 g·mol−1
3D model (JSmol)	Interactive image
SMILES O=C1N(C(=O)NC(=O)C1(C\C=C)C(C#CCC)C)C
InChI InChI=1S/C14H18N2O3/c1-5-7-8-10(3)14(9-6-2)11(17)15-13(19)16(4)12(14)18/h6,10H,2,5,9H2,1,3-4H3,(H,15,17,19) Y Key:NZXKDOXHBHYTKP-UHFFFAOYSA-N Y
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Methohexital binds to a distinct site which is associated with Cl⁻ ionophores at GABA_A receptors.^[3] This increases the length of time which the Cl⁻ ionopores are open, thus causing an inhibitory effect.

Metabolism of methohexital is primarily hepatic via demethylation and oxidation.^[1] Side-chain oxidation is the primary means of metabolism involved in the termination of the drug's biological activity.

Methohexital is primarily used to induce anesthesia, and is generally provided as a sodium salt (i.e. methohexital sodium). It is only used in hospital or similar settings, under strict supervision.^[1] It has been commonly used to induce deep sedation or general anesthesia for surgery and dental procedures. Unlike many other barbiturates, methohexital actually lowers the seizure threshold, a property that makes it particularly useful when anesthesia is provided for an electroconvulsive therapy (ECT).^[4] Its rapid recovery rate with consciousness being gained within three to seven minutes after induction and full recovery within 30 minutes is a major advantage over other ECT barbiturates.^[4]

Methohexital can be synthesized in the classic manner of making barbituric acid derivatives, in particular by the reaction of malonic ester derivatives with derivatives of urea.^[5] The resulting allyl-(1-methyl-2-pentynyl) malonic ester is synthesized by subsequent alkylation of the malonic ester itself, beginning with 2-bromo-3-hexyne, which gives (1-methyl-2-pentynyl)malonic ester, and then by allylbromide. In the final step, reaction of the disubstituted malonic ester with N-methylurea gives methohexital.