Chloral Hydrate Uses and Risks

Medical Author: Melissa Conrad Stöppler, MD
Medical Editor: William C. Shiel, Jr., MD, FACP, FACR

Chloral hydrate (Noctec, Aquachloral) is a sedative and hypnotic (meaning that it induces sleep) prescription drug that is used for the short-term treatment of insomnia. First developed in 1832, chloral hydrate is the oldest sleep medication still in use today. Other medical uses of the drug are to induce sleep before surgery and to treat post-surgical pain. Chloral hydrate has also been used for the treatment of alcohol withdrawal symptoms.

Chloral hydrate is taken by mouth as liquid syrup or a soft capsule and may also be taken in the form of rectal suppositories. Its sedative effect generally begins in about 30 minutes, and it will induce sleep in most people in about 60 minutes. The use of chloral hydrate has declined in recent years, particularly due to the development of newer sedative and hypnotic drugs, such as benzodiazepines.

Like many other sedative drugs, chloral hydrate has moderate addictive potential. While it does not produce the same degree of desperation and drug-seeking behaviors observed in those addicted to heroin, cocaine, or alcohol, chloral hydrate tolerance can develop with chronic use, meaning that repeated users may have to take greater amounts of the drug in order for it to be effective.

Chloral hydrate may lead to unpleasant side effects, including:

Toxic doses (overdoses) can cause a marked drop in blood pressure and severely compromised respiration (breathing). Signs of an overdose of chloral hydrate can include:

  • confusion,
  • seizures,
  • difficulty breathing,
  • slurred speech,
  • slow or irregular heartbeat,
  • vomiting,
  • weakness, and
  • a lowered body temperature.

Chronic use of chloral hydrate is also associated with a severe withdrawal syndrome and may induce liver damage.

Starting as early as the 19th century, chloral hydrate has often been misused and abused. The drug was often used by alcoholics in the 19th century whose sleep had become disrupted by their drinking. There are documented cases of abuse and addiction to chloral hydrate among the members of the artistic and literary population of Victorian England. Mixed in a solution of alcohol, chloral hydrate has been referred to as "knockout drops" or a "Mickey Finn." The combination of any sedative/hypnotic medication with alcohol or another type of sedative is extremely dangerous and potentially fatal, and these drugs are packaged with warnings about the serious dangers of mixing these drugs.


Last Editorial Review: 3/27/2007