This section is from the book "Materia Medica Pharmacy, Pharmacology And Therapeutics", by W. Hale White. Also available from Amazon: Materia Medica Pharmacy, Pharmacology And Therapeutics..
Camphor, although not a volatile oil, acts very much like one. Thus it is a direct cutaneous stimulant, dilating the vessels of the skin, and at first causing a sensation of warmth, but subsequently a slight degree of local anaesthesia. It is a feeble antiseptic.
Gastro-intestinal tract. - In the stomach it is mildly stimulant, dilating the vessels, increasing the flow of gastric juice and the peristalsis. Hence it is stomachic and carminative. It has a slight reflex stimulating effect on the heart. In medicinal doses it has little action on the intestines.
Absorption. - It is quickly absorbed, both from the intestines and the skin, and two bodies formed in the body from it are known. One, camphoral (one atom of H in camphor being replaced by OH), combines with glycuronic acid and is excreted in the urine as campho-glycuronic acid. Another, an amido-derivative, is also found in the urine.
Circulation. - It increases the number of leucocytes in the blood. To a slight extent the heart is excited directly by it in addition to the reflex stimulation just mentioned. And so the pulse becomes fuller and stronger; the rate is not much affected. The face may be flushed.
Respiration. - Probably some camphor or some derivative from it is excreted by the bronchial mucous membrane, the vascularity and secretion of which it consequently stimulates. It has the reputation of being a feeble expectorant.
Skin. - It is a mild diaphoretic. This effect is believed to be due to the action of the drug on the central nervous system. Probably some of the camphor is excreted by the skin, for the sweat may smell of it.
Nervous system. - Different people are differently susceptible to the effects of camphor. Five to ten grains .30 to .60 gm. will in some persons produce a feeling of exhilaration, or in others a sense of comfort and quietness. Larger doses cause excitement, giddiness, a slow pulse, and ultimately headache, burning pain in the stomach, faintness, confusion of ideas, delirium, violent convulsions, insensibility, a small, feeble pulse, and finally death from collapse. It is a mild antipyretic.
Sexual organs. - Camphor is reputed to be an aphrodisiac, but this is probably incorrect.
Its stimulating effects make camphor a favorite ingredient of many liniments. It is constantly rubbed into the skin in some form or another as a mild irritant or counter-irritant in, for example, chronic rheumatism, chronic inflammatory indurations, and the slighter chest complaints of children; and also in myalgia, neuralgia, lumbago, and sciatica, in which cases, because of its property of causing local anaesthesia, it relieves pain. In addition to the pharmacopoeial preparations, a Chloroformum Camphorae (camphor, 2, dissolved in chloroform, 1) may be used. The liquid preparations with chloral hydrate, carbolic acid, and thymol are excellent local anodynes for neuralgia, and may be dropped into a tooth to relieve toothache.
Camphor is used as a carminative, especially in neurotic subjects. It is a common remedy for a cold in the head, and is probably beneficial on account of its stimulation of the circulation and its slight antipyretic and diaphoretic effects. Many expectorant mixtures contain camphor. It has been given as an antispasmodic in hysteria and allied conditions, and some state that it is of use in cholera. Monobromated Camphor resembles, but is not identical with, the bromides in its therapeutical action, being used as a nervous sedative. Camphoric acid is successfully administered for colliquative sweating, e.g., that of pulmonary tuberculosis. The daily amount of from 15 to 75 gr.; 1. to 5. gm., should be given in the evening in divided doses at short intervals, either dry upon the tongue or in starch wafers.