Paraldehyde

PARALDEHYDE, Paraldehydum (Pharmacopoeia VII) (elaldehyde) (CH₃CHO)₃, molecular weight 132.1; a polymer of acetaldehyde, obtained by the action of concentrated sulfuric acid, zinc chloride, or phosgene on the latter (followed by neutralization of the acids with calcium carbonate). It is a transparent, colorless liquid with a specific gravity of 0.998–1.000 (0.99925 at 15°), boiling at 123°–125°, with a neutral or acidic reaction; it is easily flammable and burns with a weakly luminous flame. It is miscible with alcohol and ether in all proportions; 100 volumes of water dissolve 12 volumes of paraldehyde at 13°. Upon heating, the solution becomes cloudy due to decreased solubility, which can be used to identify paraldehyde. It has a peculiar, sharp odor and a burning taste. It contains an admixture of acetaldehyde (up to 4%), and sometimes also metaldehyde. It must be stored protected from light. It was proposed by Cervello as a hypnotic in 1883. Its local action is manifested by irritation of the mucous membranes of the digestive tract. It is rapidly absorbed; in the body, it is mostly burned, but is partly excreted, and due to its volatility, it is also excreted through the respiratory tract, which is why the exhaled air has an unpleasant odor of paraldehyde even the next day. The hypnotic effect of paraldehyde is characterized by the rapidity of the onset of sleep (10–15 minutes), its sufficient depth, duration (up to 7–8 hours), reliability of effect (according to various authors from 80% to 92%), harmlessness during prolonged use, and the almost complete absence of functional disturbances upon awakening. Experimental studies on animals and humans reveal a very insignificant effect of paraldehyde on the organs of circulation, respiration, and metabolism compared to other hypnotics, which is why paraldehyde is considered one of the most harmless among them. The side effects of paraldehyde are manifested in local irritation of the gastric mucosa, which can cause belching, nausea, and occasionally vomiting (which is why paraldehyde is contraindicated in severe disorders of the gastrointestinal tract), and an odor from the mouth that is unpleasant for the patient and those around them (which is why the use of paraldehyde is usually limited to hospital, especially psychiatric, practice). With repeated doses, habituation to paraldehyde is observed. Cases of ingestion of 100.0 with awakening after a day and a case of ingestion of 500.0 of paraldehyde over a week have been described. Several cases of fatal poisoning from the ingestion of 25.0, 52.0, etc., relate to severely ill patients, which is why a lethal dose has not been established. It is prescribed in a 5–10% solution, in a mixture with gum arabic; as a flavoring agent, Oil of Lemon, Tincture of Orange, or simply sweet tea is recommended. As a sedative in a dose of 1.0–2.0, as a hypnotic in a dose of 3.0–5.0; the maximum dose per intake is 10.0.

V. Karasik.