Gastric sedatives are substances which lessen the irritability of the stomach and thus diminish pain, nausea, and vomiting.

Their action may be either local on the stomach, or general on the nervous system, and especially on the vomiting centre in the medulla oblongata.

Local Sedatives.

Alcohol.

Alum.

Arsenious acid in minute doses.

Atropine.

Belladonna.

Bismuth salts.

Carbolic acid.

Cerium oxalate.

Chloroform.

Cocaine.

Creasote.

Ether.

Hydrocyanic acid.

Ice.

Morphine.

Opium.

Resorcin.

Silver nitrate.

Sulpho-carbolates.

General Sedatives.

Hydrocyanic acid.

Morphine.

Opium.

Anti-emetic Measures.

Recumbent posture.

Injection of large quantities of aerated water into the rectum.

The most powerful of all local sedatives is ice, and when vomiting is persistent, everything should be iced, and ice swallowed in small lumps. Hydrocyanic acid and morphine probably act by lessening the irritability of both the nerves in the stomach itself and of the vomiting centre as well. The mode of action of creasote and carbolic acid is rather uncertain, because, although they have a local anaesthetic action, yet they are found useful also in cases of reflex vomiting, such as the vomiting of pregnancy.

As adjuvants to gastric sedatives, we may mention such substances as diminish or remove the irritation, although not lessening the sensibility, of the stomach itself. Thus, where the irritant consists of very acrid fluid in the stomach, a large draught of water, by diluting it, may lessen pain, or nausea, and alkalies have a similar action. When the irritation is due to congestion of the mucous membrane, astringents will also have a sedative action. Probably this is the explanation of the use of alum in the vomiting of phthisis, and possibly, also, of the use of nitrate of silver in the vomiting of chronic alcoholism.

Uses. - Gastric sedatives are employed (1) to relieve pain in the stomach, as in gastrodynia. The most useful are small doses of morphine, hydrocyanic acid, belladonna, arsenic, and bismuth; (2) to relieve vomiting. This depends upon the cause of the vomiting. When it is due to acrid substances in the stomach, the best sedative is often a large draught of warm water, which either dilutes or renders them less irritating, or causes their removal by vomiting.

Where it is due to acute irritation of the walls of the stomach itself, ice, hydrocyanic acid and morphine, and bismuth are best.

When due to the acrid products of fermentation in the stomach, sulphurous acid, creasote, resorcin, and the sulpho-carbolates are very useful.

When due to chronic irritation and congestion, alum, nitrate of silver, creasote, carbolic acid, and the sulpho-carbolates are serviceable.

When the vomiting is due to strangulated hernia, the hernia must be reduced, and in cases of intussusception or obstruction these conditions must be removed. In the vomiting of pregnancy, the irritability of the vomiting centre must be reduced by bromide of potassium or morphine. It is only in extreme cases that the source of irritation, viz. the pregnant condition, is to be removed, but certain local means are sometimes useful; such are separation of the membranes around the neck of the uterus, which may possibly act by lessening the irritation in the organ, and painting the os uteri with stimulating applications which probably rather act by a kind of counter-irritation or inhibition.

The vomiting of pregnancy has sometimes been arrested by the injection of effervescing water, and especially of natural effervescing chalybeate water like that of Pyrmont, into the rectum in quantities of two litres at a time. It is difficult to say whether this is due to a local or general sedative action of the carbonic acid or to reflex inhibition of vomiting (cf. inhibition of sneezing, p. 246).1

1 Schucking, Deutsch. Med. Ztg., ii. 1885.