Origin. - A polymer of acetaldehyde [CH3COH].

Description and Properties. - A colorless, transparent liquid, having a strong, characteristic, but not unpleasant, pungent odor, somewhat resembling that of chloroform, and a burning, cooling taste. Soluble in 8 parts of water at 250 C. (77 F.) and in 16.5 parts of hot water, being, as will be observed, more soluble in the former than in the latter. Miscible in all proportions with alcohol, ether, and fixed and volatile oils.

Dose. - 1/4-1 fluidrachm (1.0-4.0 Cc.) [30 minims (2 Cc), U. S. P.].

Physiological Action. - Externally and Locally. - Antiseptic, antifermentative. In general its action is like that of alcohol.

Internally. - Digestive System. - Paraldehyde has little action upon the digestive tract. It may cause indigestion.

Circulatory System. - It differs from chloral in affecting the circulatory system favorably in medicinal doses, tending rather to slow and strengthen the pulse. Toxic doses weaken the heart and lower arterial pressure, the heart's action ceasing in diastole.

Nervous System. - Its influence upon the brain and spinal cord is similar to that of chloral. The sleep it induces, however, is not so prolonged as that caused by the latter drug, more frequent doses being required for continued soporific effects. The sequelae of paraldehyde are not unpleasant.

Respiratory System. - Its action resembles that of alcohol, although it is not so powerful a respiratory depressant as the halogen derivatives of alcohol. In toxic doses death usually ensues from paralysis of the respiratory center.

Absorption and Elimination. - Paraldehyde is eliminated by the lungs and kidneys, the excretion of nitrogen and phosphorus being somewhat lessened.

Temperature. - Like alcohol, it lowers the temperature, but in less degree.

Untoward Action. - It occasionally causes irritation of the mucous membranes and erythematous eruptions.

Poisoning. - The symptoms of poisoning are similar to those of chloral. Fatty degeneration of the heart and liver have been found, together with disorganization of the red corpuscles.

Treatment of Poisoning. - The same as in poisoning from chloral.

Therapeutics. - Like those of chloral. Paraldehyde is more hypnotic than anodyne, appearing to be best adapted to relieve so-called idiopathic insomnia. It is a better diuretic than chloral, and in certain degenerated conditions of the heart and arteries, where a diuretic as well as hypnotic is desirable, paraldehyde serves as a valuable remedy.

Administration. - It may be given in capsules, or, when otherwise administered, its unpleasant taste may be disguised by giving it in an emulsion flavored with orange or bitter almond. Glycerin also renders it quite palatable, yet it is always more disagreeable to the taste than chloral, besides lending to the breath an offensive and persistent odor.