Drug information of Paraldehyde


Paraldehyde is classified as a central nervous system (CNS) depressant and has also been found to be an effective anticonvulsant, hypnotic and sedative agent due to its CNS depressant properties.

Mechanism of effect

Paraldehyde is believed to reduce the release of acetylcholine in response to neuronal depolarization. The exact mechanism of this effect is unknown.


Paraldehyde blocks neuromuscular transmission.


Absorption: 93% of orally administered paraldehyde is absorbed from the gastrointestinal tract.

Metabolism: Paraldehyde is believed to undergo depolymerization to acetaldehyde followed by oxidation by aldehyde dehydrogenas. It is thought to ultimately be metabolized to carbon dioxide and water.

Route of elimination: 70-80% is metabolized to carbon dioxide and subsequently exhaled. 11-28% is exhaled as the parent compound. 0.1-2.5% is excreted in the urine as the parent compound.

Half life: The mean half life is 7.5 hours in a range if 3.5-9.5 hours.

Drug indications



Not available


  • Alcohol abuse (or history of) or
  • Drug abuse or dependence (or history of)—Dependence on paraldehyde may develop
  • Colitis—Paraldehyde used rectally may make the condition worse
  • Emphysema, asthma, bronchitis, or other chronic lung disease, or
  • Liver disease—Higher blood levels of paraldehyde may occur, increasing the chance of side effects
  • Gastroenteritis (stomach flu) or
  • Stomach ulcer—Paraldehyde taken by mouth may make the condition worse

Points of recommendation

Use paraldehyde only as directed by your doctor. Do not use more of it, do not use it more often, and do not use it for a longer time than your doctor ordered. If too much is used, the medicine may become habit-forming.

Do not use if liquid turns brownish in color or if it has a strong vinegar-like odor, since this means the paraldehyde is breaking down.

For patients taking paraldehyde by mouth:

  • Do not use a plastic spoon, plastic glass, or any other plastic container to take paraldehyde, since paraldehyde may react with the plastic. Use a metal spoon or glass container.
  • Take paraldehyde mixed in a glass of milk or iced fruit juice to improve the taste and odor and to lessen stomach upset.

For patients using paraldehyde rectally:

  • Do not use paraldehyde in any plastic container since it may react with the plastic.
  • Before using paraldehyde rectally, make sure you understand exactly how to use it. Paraldehyde may need to be diluted.

Do not stop using it without first checking with your doctor. Your doctor may want you to reduce gradually the amount you are using before stopping completely.

Keep paraldehyde away from the eyes and avoid getting it on the skin and clothing.

Keep paraldehyde away from heat, open flame, and sparks.

Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.

If you miss a dose of paraldehyde, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

Paraldehyde will add to the effects of alcohol and other CNS depressants (medicines that slow down the nervous system, possibly causing drowsiness). Some examples of CNS depressants are antihistamines or medicine for hay fever, other allergies, or colds; sedatives, tranquilizers, or sleeping medicine; prescription pain medicine or narcotics; barbiturates; medicine for seizures; muscle relaxants; or anesthetics, including some dental anesthetics. Check with your doctor before taking any of the above while you are using paraldehyde.

Before you have any medical tests, tell the medical doctor in charge that you are taking paraldehyde. The results of some tests, such as the metyrapone test and the phentolamine test, may be affected by paraldehyde.

Paraldehyde may cause some people to become drowsy or less alert than they are normally. Even if taken at bedtime, it may cause some people to feel drowsy or less alert on arising. Make sure you know how you react to paraldehyde before you drive, use machines, or do anything else that could be dangerous if you are not alert.

Pregnancy level

Group c - Not adequate studies in pregnant women

Related drugs

Chloral hydrate , Ethchlorvynol

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