Equithesin is the proprietary name for a commercial mixture of chloral hydrate

Chloral hydrate

Chloral hydrate is a sedative and hypnotic drug as well as a chemical reagent and precursor. The name chloral hydrate indicates that it is formed from chloral by the addition of one molecule of water. Its chemical formula is C2H3Cl3O2....

, magnesium sulfate

Magnesium sulfate

Magnesium sulfate is a chemical compound containing magnesium, sulfur and oxygen, with the formula MgSO4. It is often encountered as the heptahydrate epsomite , commonly called Epsom salt, from the town of Epsom in Surrey, England, where the salt was distilled from the springs that arise where the...

 and pentobarbital sodium that was used as a general anesthetic in horses. Equithesin was administered intravenously to effect and for many years was the most commonly used injectable anesthetic in horses. Newer anesthetic agents such as injectable barbiturates, alpha-2 agonists, cyclohexylamines, guaifenesin

Guaifenesin

Guaifenesin INN or guaiphenesin , also glyceryl guaiacolate, is an expectorant drug sold over the counter and usually taken by mouth to assist the bringing up of phlegm from the airways in acute respiratory tract infections.-History:Similar medicines derived from the guaiac tree were in use as a...

and inhalants gradually replaced Equithesin. The drug has been off the market and unavailable for decades.