A product of the polymerization of Ethylic Aldehyde by means of various Acids or Salts. For example, Ethylic Aldehyde may be acted on by Hydrochloric Acid, Carbonyl Chloride (Cocl2), Sulphur Dioxide or Zinc Chloride; during the action, the temperature of the mixture rises, and almost complete conversion into Paraldehyde takes place. On cooling to below 320 F. 0° C, Paraldehyde crystallizes. 3C2H4O=C6H12O3.


A colorless transparent liquid, having a strong, characteristic, but not unpleasant or pungent odor, and a burning and cooling taste. Solubility. - In 85 parts of water; freely in Alcohol and Ether. Dose, 1/4 to 1 fl. dr.; 1. to 4. c.c

Action of Paraldehyde


It is antiseptic.


Large doses increase the flow of urine and somewhat strengthen the heart, but they do not affect the gastrointestinal tract or respiration; enormous doses of paraldehyde weaken the action of the heart, and kill by paralysis of the respiratory centre.

Nervous System

It is a powerful hypnotic, without any unpleasant after-effects. It acts quickly, and the sleep, which lasts several hours, is quiet, refreshing, and dreamless. Paraldehyde in toxic doses paralyzes the anterior cornua of the spinal cord; thus it abolishes reflex action and causes paralysis. It does not affect nerves or muscles.

Therapeutics of Paraldehyde


It is given solely as an hypnotic in the same class of cases as chloral, and as it does not act on the heart it may also be used for patients suffering from cardiac disease. It has been used largely in asylums to produce quiet in mania, and sleep in melancholia. It may produce an erythematous rash. Unless given in capsules, the great objection to its use is its disagreeable taste, which is best covered by prescribing it with syrup and tincture of orange peel in at least two fluid ounces 60. c.c of water to insure that a usual dose will be dissolved. It can also be administered in glycerin in a 25 per cent. solution, which renders it more palatable. It gives an extremely offensive and persistent odor to the breath, which lasts many hours. Instances of the paraldehyde habit have been occasionally reported. There is great emaciation, cardiac weakness, unsteady gait, mental confusion and agitation with hallucinations of sight and hearing and unpleasant delusions. Restraint for several months is necessary for cure.