Caffeine (Theine),—is officially described as a feebly basic, proximate principle, obtained from the dry leaves of Thea Sinensis (the tea-plant), or from the dry seeds of Coffea Arabica, (the coffee tree), and also found in other plants. The principles Caffeine and Theine are therefore officially declared to be identical, but their identity with Guaranine is left unsettled. The Caffeine of commerce is usually obtained from old tea-leaves. It contains more nitrogen than almost any other proximate vegetable principle, and occurs in colorless, flexible crystals, which are soluble in 80 of water and in 33 of alcohol. Dose, gr. j-v.

The Coffee-Plant, Coffea Arabica, is a small tree of the nat. ord. Rubiaceae, 15 to 30 feet high, native of South Arabia and Abyssinia, but cultivated in various parts of the world. Its seeds contain Caffeine 0. 2 to 0.8 per cent. (partly free, partly as a tannate), tannic and caffeic acids, sugar, legumin, etc. By roasting them, part of the caffeic acid is converted into methylamin, the sugar is changed into caramel, and several volatile substances are formed, which give to coffee its peculiar aroma and some of its stimulant qualities, and are collectively known as Caffeone, one of them being called Caffeol.

The Tea-Plant, Thea Sinensis, is a native of China and Japan, and a member of the nat. ord. Ternstromiaceae. Besides Theine (Caffeine), it also contains Tannic Acid and a volatile oil, the latter of which is most abundant in green teas.


Caffeina Citrata, Citrated Caffeine,—is a very uncertain mixture, and is not looked upon as a definite compound. Dose, gr. ij-x.
Caffeina Citrata Effervescens,—Dose, ʒj-ij, in a glassful of water.
*Extractum Caffeae Viridis Fluidum, Fluid Extract of Green Coffee (Squibb),—intended as a substitute for the fluid extract of Guarana. Dose, ʒss-ij.

Physiological Action. Caffeine is at first a stimulant, and subsequently a paralyzant, to the nerve-centres in the cerebrum, medulla and cord. In small doses it quickens the action of the heart and raises arterial tension; stimulates the cerebral functions, by increasing the supply of blood to the brain; increases the respiration rate and the secretion of urine. Larger doses (gr. v-viij), often over-stimulate the cerebral circulation, causing thereby great heaviness of the head, flashes of light before the eyes, tinnitus aurium, insomnia, restlessness, and even delirium,—the pulse becoming rapid, feeble, irregular and intermittent, and the general body-temperature elevated, though that of the periphery may be lowered. Large doses depress the heart and respiration, and lower the blood-pressure;—in the smaller animals exalting the reflex excitability of the cord and producing tetanic convulsions, and in lethal doses paralyzing the cardiac muscle as well as its motor ganglia, but causing death by paralysis of respiration. It powerfully affects muscular fibre, both voluntary and involuntary kinds, throwing it into a state of tetanic contraction resembling rigor mortis. If administered in sufficient quantity it would doubtless prove fatal to man,—but its lethal dose for him would be very large. Caffeine is excreted unchanged in the bile and urine, and is a reliable hydragogue diuretic; acting by stimulation of the secreting apparatus in the kidney, as well as by generally raising the arterial tension. (Brunton.)

The Common Stimulant Beverages Compared.

The Qualities possessed in common by these substances, and for which they are so universally esteemed by mankind, are three-fold. They all (1) retard the retrograde metamorphosis of the body-tissues, (tissue-waste);—thereby enabling the work of the individual to be done upon a smaller supply of reparative material, (food), and with less fatigue. Furthermore, when used in moderation, they are all (2) more or less stimulating to the mental processes, and (3) sedative to the nervous system.

This similarity of action they owe to the possession of principles, which, if not identical, are so closely related to each other that until very recently they have been so considered both by chemists and pharmacologists. Their divergence from each other, in the finer shades of their action, depends most probably on the existence in each of differing aromatic and volatile principles, which modify the action of the alkaloid in some degree. Similar principles are developed in them by the various processes of preparation, (as roasting, drying, etc.), all of which have some part in determining the general action of the beverage containing them.

Coffee, if used with moderation, assists digestion, promotes intestinal peristalsis, allays the senses of fatigue and hunger, lessens tissue-waste and consequently decreases the formation and excretion of urea (?). Used to excess it disorders digestion, and causes functional disturbances of the nervous system, shown by headache, vertigo, mental confusion, and palpitation of the heart. It increases secretion, blunts sensation, exalts reflex excitability, increases mental activity, and may produce insomnia and great nervous restlessness. It first briefly stimulates the heart and raises arterial tension, but soon depresses both. The wakefulness is usually preceded by a brief period of drowsiness.

The brief stimulation of the intellect, consequent on drinking a cup of good coffee, cannot be obtained from an infusion of raw coffee, and is probably due to the volatile constituents developed in roasting. Caffeone opposes Caffeine in its action on the circulation, as it quickens the pulse and lowers arterial tension. Its action, however, is of brief duration, and soon gives way to the influence of the principal constituent. The Tannin is the ingredient which enables it to produce dyspepsia, and is most abundant in those infusions which are kept a long time on the stove before being served.

The green bean produces very different effects from those of the roasted one, exhibiting the action of Caffeine alone, unmodified by that of the empy-reumatic products. A tincture of green coffee, besides being an efficient diuretic, has marked anti-lithic powers, and promotes the elimination of the poison of gout from the system.

Tea is the most refreshing and stimulating member of the group. Used to excess, it powerfully affects the stability of the motor and the vaso-motor nerves, the action of the heart, and the digestive function,—producing flatulent dyspepsia, tremulousness of the limbs, pallor of the surface, irregular cardiac action, and feeble impulse, hallucinations, nightmare, anorexia, headache, nausea and vomiting, obstinate neuralgiae-especially of the supraorbital and occipital nerves; also constipation, and a pain in the left side are not infrequent. The condition of chronic tea-poisoning is termed "Theism,"—and is very often seen among women of the lower class in cities, who do not indulge in alcoholic beverages, but freely accept the dominion of the "cup that cheers" and worse than inebriates.

Maté (Ilex Paraguayensis, Paraguay tea), is supposed to be intermediate in its effects between tea and coffee. It also contains Caffeine, in the proportion of 1.2 per cent.

Guarana (Paullinia Cupana of Brazil), contains an alkaloid—Guaranine, in the proportion of 5 per cent., which is probably identical with Caffeine, though some think it more analogous to Theine. It is especially noted for relieving a nervous headache, for which purpose the official fluid extract may be used in doses of ♏︎xx, three or four times daily, when the basis of that preparation happens to be of good quality.

Coca, or Cuca, (Erythroxylon Coca, see page 126), is more sustaining and less of a direct stimulant, than either tea or coffee. The proportion of Cocaine in the leaves varies greatly in different samples, as they occur in commerce. (Cola contains caffeine. Coca does not. -Henriette)

Cocoa (Theobroma Cacao, the Chocolate-tree), is more directly nutritious than any of the group, containing a large quantity of fat, Oleum Theobroma, (cacao-butter), which makes it difficult of digestion to many persons. Its alkaloid, Theobromine, is closely allied to Caffeine, the latter being considered a Methyl-theobromine. The various preparations of this agent are made from the seeds, after the oil has been expressed from them. They are ground in a mill, mixed with rice, barley, sugar, flour, etc., and put up in powdered form, called Cocoa,—but if flavored with vanilla and pressed into a cake, the product is Chocolate. The thin husks which envelope the seeds are known as "Shells," and are used to make a beverage similar to but milder than cocoa or chocolate.

Therapeutics. Although without a very extensive range of usefulness, Caffeine is a valuable stimulant in many forms of nervous and cardiac depression, and has proved especially efficacious in—

Headaches of neuralgic or nervous type, the pain being general over the head,—gr. j of Caffeine every half hour, or the fluid extract of Guarana, in 20-minim. doses every 2 or 3 hours.
Choleraic Diarrhoea, and that of phthisis,—it checks outward osmosis by stimulating the depressed nervous apparatus.
Dropsy, cardiac and renal,—Caffeine as a diuretic and cardiac stimulant.
Cervico-brachial Neuralgia,—Caffeine hypoder., gr. j, increased to gr. v.
Lithaemia and Gout,—a tincture of the green bean has marked diuretic and antispasmodic powers, and is very useful in these conditions.
Insomnia of chronic alcoholism,—gr. ½ of Caffeine hypodermically.
Adynamic Fevers,—it may well be used in place of alcoholic stimulants.
Intermittents,—Coffee has a curative reputation among the inhabitants of the Philippines, which is corroborated by the Dutch physicians.
Asthma,—if not used habitually, Coffee is valuable in the paroxysm.
Opium Narcosis,—Caffeine hypodermically, or better still, strong black coffee, to antagonize the increasing torpor of the nervous centres.
Neuralgia of any kind, cervico-brachial, sciatic, etc.,—Theine, in doses of gr. ⅙ to gr. ½ hypodermically, is efficient, and may be kept up as long as required. To make a cure, however, the nutrition of the nerves must be attended to.
Locomotor Ataxia, Lumbago, etc.,—Theine has been used with prompt benefit, in the same manner, promptly relieving pain, without producing any narcotic effect. (Mays.)

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