Source and Composition. Like the major number of the newest antipyretics, which are related either to Chinolin or to Phenol, Acetanilid is a derivative of Anilin, from which it is obtained by the action thereon of glacial acetic acid, substituting the organic radical Acetyle for an atom of hydrogen. Chemically, it has the name Phenyl-acetamide, and the formula C6H5NHC2H3O.

The name Antifebrin is copyrighted by its original promoters for trade purposes, and therefore should be dropped from professional usage.

Characteristics. A pure white and crystalline powder, of neutral reaction, odorless, but of slightly burning taste. It melts at 235° F., and distils at 557° F.,—is soluble freely in alcohol, wine, etc., but very sparingly (1 in 190) in cold water, and a little more readily in hot water. It is a neutral substance, being unaffected by hydrochloric or sulphuric acids, and ordinarily so by alkalies.

Dose and Administration. The dose ranges from gr. ij to gr. x, repeated twice, but not exceeding gr. xxx in the 24 hours. It may be administered in compressed tablets;—also in powders, or in dilute alcoholic solution. As an antipyretic, gr. iij may be administered every ¼ to ½ hour, until 12 or 15 grains have been given, which will usually be a sufficient quantity, especially if given at the acme of the febrile movement.

Analogues of Acelanilid.

*Phenacetinum, Phenacetin, (Oxyethyl-acetanilid), C10H18NO2—also designated Para-acet-phenetidin,—is produced by the action of glacial acetic acid on para-phenetidin, a body obtained from phenol. It is closely allied in chemical composition to Acetanilid, and occurs in colorless, glistening scales, soluble in about 16 of alcohol, sparingly in water. It is probably the safest of the new synthetical antipyretics, reducing pyrexia gradually, and causing perspiration, without producing collapse. It is also anodyne and hypnotic, soothing pain and producing sleep. Dose, gr. ij-xx; as an antipyretic, gr. viij-x hourly or every 2 hours, in powder or tablets;—against neuralgia and rheumatism gr. xv, repeated if necessary, up to ʒjss in 24 hours.
*Phenocoll Hydrochloride,—is another synthetical antipyretic, closely allied to the preceding, both chemically and medicinally, and distinguished by its comparatively free solubility, gr. xv dissolving readily in ℥j of water. It has decided power as an antipyretic, antirheumatic and analgesic, with the decided advantage that it has no injurious effect upon the blood corpuscles, even when in direct contact with them. Dose, gr. v-xxx, an average dose being about gr. xij, three or four times a day.

Physiological Action. Acetanilid is a very efficient antipyretic, besides being strongly analgesic and antispasmodic, lessening the reflex action of the spinal cord, and inhibiting the sensibility of sensory nerves. It raises the arterial tension somewhat, and slows the heart in a corresponding degree.

Compared with the action of Antipyrin, the effect of Acetanilid on the body-temperature is manifested more slowly (1 hour against ½ hour),—but lasts a longer time (6 against 2 hours). It is markedly diuretic, somewhat diaphoretic; is a cerebral, muscular and vaso-motor stimulant, and leaves no ill after-effects;—while Antipyrin is powerfully diaphoretic, a cerebral sedative, and produces great depression. Furthermore, Acetanilid produces the same degree of reduction of body-temperature as Antipyrin, with the ingestion of but ¼th the dose; and, like the latter agent, it has little or no effect on the normal temperature, and its continued use begets tolerance of its action. Its antipyretic action corresponds, in degree and in duration, to the size of the dose,—the pulse is slowed, and quiet sleep often follows. There is neither vomiting nor diarrhoea afterwards, but there is a tendency, in some few cases, to collapse, with chills and cyanosis, especially the latter, during the period of depressed temperature. A toxic dose destroys the ozonizing function of the blood, forming methyl-haemoglobin. The heart, liver and kidneys are found in a state of acute fatty degeneration, in animals poisoned thereby.

Therapeutics. Besides being one of the most efficient antipyretics, Acetanilid has marked analgesic and antispasmodic powers; and these, together with its great advantages of a small dose, efficiency and safety, and the absence of the severe rigors and cardiac depression which mark the chinolin derivatives, combine to make it one of a wide therapeutical range. It is especially useful in—

Phthisis and Typhoid Fever,—for the hyperpyrexia, and thereby relieving wakefulness, lessening delirium, and upholding a failing heart; but it should not be used continuously for any great length of time in these affections.
Pains of Locomotor Ataxia,—and in those of rheumatic origin, sciatica, lumbago, etc., it is a most efficient remedy.
Acute Rheumatism,—it is highly praised; though its efficiency is herein disputed by Salol, as also by Salipyrin.
Epilepsy,—it is being tried, with a view of moderating reflex excitability.
Epidemic Influenza,—both as a prophylactic and a remedy, Phenacetin has proved highly efficient.
Migraine,—has been treated with benefit by Phenacetin in 2-grain doses with gr. ss of Citrated Caffeine.

A Compend of Materia Medica, Therapeutics, and Prescription Writing, 1902, by Sam'l O. L. Potter, M.D., M.R.C.P.L.