Dose.— From grs. v. to ʒj.
Physiological Action.—The physiological action of chloral has been differently interpreted. Liebrich, who first discovered its hypnotic action, also Richardson and Personne, who have thought that they had discovered chloroform in the air breathed out by men and animals treated with chloral, ascribed it to a decomposition of chloral in the body, and its conversion into chloroform by the alkaline blood. But closer examination proved that almost all the chloral taken into the body passed with the urine in the shape of urochloral, and only a very small quantity of chloroform is formed by contact of chloral with blood, even for some time. It must, then, be rather due to the property common to diffusible chlorides especially of organic origin, upon the cerebro-spinal centers. Chloral hydrate acts primarily and directly upon the gray substance of the medulla oblongata, some gray substance of the cortex, and upon the poisterior tubercular quadrigemina. The respiratory centers are primarily affected, and from them a reflex action is exerted upon depressory libres of the pneumogastric of the heart, causing a reduced pressure of the blood in the arterial system, when moderate doses are taken. In large doses, the psycho-motor and motor fibres of the gray mass of the cortex of the middle cerebral lobe, are there included in its action, which is then intensified, the circulation and respiration much affected, and complete muscular relaxation produced. The center of the common sensation is temporarily paralyzed. The sensation of the skin and the vegetative function of the body are but imperceptibly disturbed.
Direct action upon the blood by chloral is very slight, nor does it coagulate albumen to any extent. Clots found in the vessels after fatal doses of chloral, are due to the stasis of the blood in the vessels from lack of propelling power in the heart and arteries. The hypnotic action seems mostly due to a suspension of the action of the conducting fibres from the sensory to the motor centers. No impression being carried from the sensory center to the motor, and especially psycho-motor, the body rests, that is, it is in an inactive state, very much akin to that of natural sleep and hybernation. It is in no wise an anaesthetic; but the lack of perception of sensation is there, the same as all reflex motion (except that carried on in the vegetative organs) is extinct.—Prof. Jeancon.
Therapeutic Action.—It has been asserted that chloral as good a poison as strychnia. Chloral, like all powerful drugs, has a therapeutic and a poisonous action. Whether it will act as a poison or as a medicine will be determined by the quantity given and the circumstances under which it is administered. It is a well established fact that the drug in full doses epresses the centers at the base of the brain, renders respiration slower, weakens the heart's action, lowers the temperature, and produces muscular relaxation. It follows, then, that chloral, in cases of great depression, is a poison. It should never be given when the heart action is feeble.
As a hypnotic, by its action on the cerebrum, chloral is valuaible when sleeplessness results from great excitement of the nervous system. When inability to sleep results from severe pain, chloral is inferior to many drugs that we possess.
As an antispasmodic, when not contra-indicated by depression, we may employ it in spasmodic diseases. Puerperal convulsions may be checked by the drug. After a full dose of morphia administered hypodermically, the patient may be kept quiet with chloral. In tetanus chloral will help to control spasm, but too much reliance must not be placed in it.
In delirium tremens the drug is much relied upon by some physicians, and often improperly administered; the depression met with in old topers renders chloral a dangerous hypnotic. In those cases where we have great excitement, increased temperature, and flushed face, chloral may be employed to produce sleep. Where the face is pale, skin bathed in perspiration, circulation feeble, and muscular system relaxed, chloral is contra-indicated.
In acute mania, with inability to sleep, we may place great reliance on chloral; if not contra-indicated I regard it as the best hypnotic at our command.
In cases where great increase of temperature with excitement and inability to sleep follow surgical operations, chloral may be employed as a hypnotic with great advantage.
In obstetrical practice, I have used chloral with good effect. The distressing pains in the first stage of labor, may be rendered less exhausting, and rigidity of the soft parts overcome with this drug; severe after pains may be quieted with chloral.
As a local application, chloral may be used as a stimulant and deodorizer to indolent and bad smelling wounds. Twenty grains to the pint of water forms a good application. Triturated with camphor in equal proportions, it forms a fluid which, if painted upon parts suffering with neuralgia, gives at least temporary relief.—Prof. Locke.