This section is from the book "Materia Medica And Therapeutics - Vegetable Kingdom", by Charles D. F. Phillips. Also available from Amazon: Materia Medica And Therapeutics: Vegetable Kingdom.
Active Ingredient. - The physiological properties of capsicum are represented by capsicine, a yellow, thick semi-solid, which melts with heat, and is soluble with difficulty in water, but easily in ether, turpentine, and rectified spirit.
Physiological Action. - The local irritant action of cayenne pepper is well known; it excites a burning sensation in the mouth and tongue, and, if swallowed, in the fauces and throat. Should this action be carried to intensity severe inflammatory swelling of the mucous membrane is produced, with copious out-pour of saliva. In the stomach small quantities excite a gentle and not unpleasant feeling of warmth; very large doses cause severe gastric and intestinal inflammation; the prolonged use of large (though not acutely poisonous) doses diminishes appetite and digestive capacity: these evil effects, however, are not so readily produced in persons who reside in the tropical countries to which the capsicum is indigenous. Applied to the skin, especially in concentrated solution, capsicum is a powerful rubefacient, and will even blister if applied continuously.
1 Guide to Therapeutics, London, 1877. 2Abh. u. d. ven. Krankh, Gottingen, 1788.
As regards the more remote physiological actions of capsicum nothing can be said to be known with certainty. It does not appear, in any dose, to exercise narcotic power, but large doses would seem to increase the perspiration and the flow of saliva, whether by simply producing vasomotor paralysis, or in some other way, is not known. The sweating of the brow and the salivation, which are immediately produced by a very large dose of cayenne, are probably due to reflex paralysis of the vasomotor fibres which run with the branches of the fifth nerve.
Finally, it may be mentioned that capsicum is eliminated, in part, in the urine.
Therapeutic Action. - The most important medicinal action, probably, of capsicum, is one which has only been observed of late years. It had been suspected, indeed, that this drug was a general nervous stimulant, but no proof existed of its acting in this way upon the nervous centres, and especially on the brain, until the remedy came to be used for delirium tremens. The remarkable success which has attended the use of cayenne pepper in this disease seems to have made strangely little impression upon British practice. Kinnear, Lawson, and Lyons have administered the pepper in doses of from 20 to 80 grains, single or repeated doses; the last-named authority believing that the effect is produced in a reflex manner, the nerve ends of the vagi in the stomach being the point of original impression.1 He considers that capsicum has many advantages over digitalis, especially in those recurrent and similar cases which are so often attended by fatty heart. Kinnear and Lawson treated not less than seventy or eighty cases successfully with capsicum alone.
Other examples of the general stimulant action of capsicum, more commonly known, but not so decisive in their character, are its employment in atonic gout, in paralysis, in dropsy, in tympanitis, and in the debilitated stages of fever. Much smaller doses (1/2 grain to 2 grains every four hours) than are needed in delirium tremens are here available. For scrofulous constitutions capsicum may be usefully combined with iron. In intermittents it is said to be a useful adjunct to cinchona.
In scrofulous and fistular ulcerations a weak infusion of capsicum becomes a useful stimulant.
In the coma of fever, when rubefacient cataplasms are required for the feet, the same medicine furnishes a desirable ingredient.
Capsicum enters likewise into the composition of various kinds of throat-lozenges, and of preparations sold under the name of "cardiac tinctures."
Capsicum is a useful stimulant, again, in dyspepsia; and in cases of flatulency arising from vegetable diet it is an excellent carminative.
In cynanche tonsillaris, or common inflammatory sore-throat, which manifests itself with fever, pains and swelling of the tonsils, a thickly-furred tongue, a profuse discharge of viscid saliva, and the very disagreeable symptoms of deglutition accomplished with much difficulty, and a return through the nostrils of the fluids attempted to be swallowed, a gargle of capsicum rarely fails to give relief, provided it be used in the stage of the disorder which precedes suppuration.
1 Med. Prees and Circular, April 18, 1866.
In cases likewise of cynanche maligna, so commonly met with in conjunction with scarlatina, capsicum is highly beneficial.
In the form of cayenne pepper it is useful in ordinary sore throat; also in relaxed sore throat, and in relaxed uvula. Care should be taken when this gargle is employed, as it occasionally induces violent inflammation, which is by no means easily subdued.
Spasmodic, irritating coughs, which arise from elongated uvula and relaxed throat, are again amenable to capsicum; as are likewise atonic dyspepsia, accompanied by heartburn and diarrhoea. In the former cases the gargle should be prepared with honey.
I have employed capsicum in tincture, and have also used it externally for habitual pain in the loins, attended by sluggish circulation in the renal vessels, and where there was a slight but persistent trace of albumen in the urine. The symptoms in these cases had baffled all previous treatment, yet were speedily removed by a steady course of capsicum, the dose being five minims taken thrice a day, and a capsicum cataplasm being applied for two or three nights in the week. (Capsicum decidedly promotes the action of quinine in malaria, and, together with a little opium, may be combined in the following proportions: quinine, ten grains, capsicum, five grains, opium one-half to one grain, these to be mixed and divided into such doses as may be required.)
Preparations and Dose. - Capsicum, gr. i. - v. (.06 - .30); In-fusum Capsici, 3 ij. - iv. (8 - 15.); Oleo-resina Capsici, gr. ss. - j. (.03 - .06); Tinct. Capsici, M.v. - xxx. (.30 - 2.)