Hydrocyanic acid is a remedy of very considerable utility in certain affections involving the functions of the pneumogastric nerve. It is often highly serviceable in various kinds of nervous vomiting; for example, the vomiting of pregnancy, the vomiting which accompanies some cerebral disorders, and the reflex vomiting of phthisis. The good effects are quickly, if at all, produced; hence, if no result is attained after some days' administration, no advantage can be expected from its continued administration. Rx Acid, hydrocyan. dil., 3 j; aquae laur.-cerasi, oz ij. M. Sig.: A tea-spoonful every two to four hours.

Gastralgia, when it is a truly neuralgic affection of the gastric nerves, is occasionally very quickly cured by this agent. Sometimes cases, apparently in every way suitable for its use, are not improved by it. If a few doses do not effect any amelioration, it will be useless to continue it. Cases of indigestion accompanied by pain in the nucha, and attacks of giddiness (stomachal vertigo), are sometimes remarkably relieved by prussic acid. Irritative dyspepsia, manifested by these symptoms, a red-glazed tongue, pain, epigastric tenderness, and a feeling of weight and oppression, may be, not infrequently, much benefited, and, indeed, cured; but while the results are often brilliant, failures are also frequent. Enteralgia, a malady often extremely rebellious to remedies, not infrequently yields promptly to prussic acid.

Considerable medicinal doses of this agent are very fatal to round worms (lumbricoides).

Hydrocyanic acid is a successful remedy in whooping-cough, after the subsidence of the catarrhal symptoms. It acts by allaying irritability of the pneumogastric, and is successful just in proportion to the preponderance of the nervous symptoms. The cases in which the author has witnessed the best results were cases of cough by habit, after the cessation of the whooping-cough proper. The nervous cough of mothers, which exists during the presence of whooping-cough in the household, may be allayed by this agent. Rx Acid. hydrocyan. dil., 3j; tinct. sanguinariae, 3 iv; syrp. senegae, oz ss; syrp. tolutan., oz ij; aquae lauro-cerasi, 3 vij. M. Sig.: One or two tea-spoonfuls, according to age, every three or four hours. For irritable cough. It sometimes happens that this agent will greatly relieve the cough of phthisis, but only when it is chiefly nervous.

To allay cerebral irritation and excitement, prussic acid has been employed with benefit (McLeod). In forty cases of mental disorder observed by McLeod, there was "slight or temporary amelioration" in ten; a "more decided and permanent effect," the disease being still stationary or progressive, in nineteen; and in eight cases, six of acute mania, and two of acute melancholia, "the drug has been a factor, and a very main one, in rapid restoration to reason." In the treatment of these cases, McLeod used from two to five minims of Scheele's dilute acid, which contains five per cent of anhydrous acid. His method of administration consisted in giving it at first at short intervals (every quarter of an hour), and, when effects were produced, every hour or two. He also employed it subcutaneously, in five-minim doses.

External Uses

In various cutaneous diseases characterized by itching, the local application of prussic acid affords relief. The following formulae, from Fox, represent serviceable combinations: Rx Bichloride of mercury, gr. j; dilute hydrocyanic acid, 3 j;. emulsion of almonds, oz vj. M. Use in itching, in lichen, in the syphilodermata. Rx Dilute hydrocyanic acid, 3 ss to 3 j; infusion of marsh-mallow, oz v to oz viij. M. Use in pruritus. Rx Acetate of ammonia, oz j; dilute prussic acid, 3 jss; infusion of tobacco, oz viij. M. Sig.: To be sponged on the part twice a day in pruritus ani or p. vulvae. Rx Borax, 3 j; prussic acid, 3 ij; rose-water, oz viij. M. In the pruritus of old people.

Authorities referred to:

Amory, Dr. Robert. The Boston Medical and Surgical Journal, vol. ii, 1866, p. 73. Casper, von Dr. Carl Liman. Gericht. Medicin., zweiter Band, p. 521. Hermann, Dr. L. Lehrbuch der experirnentellen Toxicologie Blausäure, p. 288. Hoppe-Seyler. Archiv fur path. Anat., Band xxxviii, p. 435. Ibidem. Tübinger med. chem. Unler., p. 206. Husemann, Dr. Theod. Handbuch, etc., zweiter Band, p. 1136. Jones, Dr. Joseph. The Medical Record, New York, vol. ii, p. 459. Kolliker, Prof. Dr. Archiv für path. Anat., Band x, p. 272.

LecorchÉ et Meuriot, MM. Archives Générales de Méd., tome xi, 6 sér., p. 530, et seq.

McLeod, Dr. Kenneth. The Medical Times and Gazette, vol. i, 1863, p. 262. Preyer, Dr. W. Die Blausäure, phys. Untersucht, Bonn, 1868-'70. Taylor, Dr. A. S. On Poisons, third London edition, p. 585, et seq.