The oldest of the hypnotic (sleep inducing) depressants, chloral hydrate was
first synthesized in 1832. Marketed as syrups or soft gelatin capsules, chloral
hydrate takes effect in a relatively short time (30 minutes) and will induce
sleep in about an hour. A solution of chloral hydrate and alcohol constituted
the infamous "knockout drops" or "Mickey Finn." At therapeutic doses, chloral
hydrate has little effect on respiration and blood pressure but, a toxic dose
produces severe respiratory depression and very low blood pressure. Although
chloral hydrate is still encountered today, its use declined with the introduction
of the barbiturates.