The hydrochlorate of an alkaloid obtained from the leaves of Erythroxylon Coca.

1 United States Dispensatory, p. 1017.

Preparation. - It may be obtained by agitating with ether an aqueous solution of an acidulated alcoholic extract, made alkaline with carbonate of sodium; separating and evaporating the ethereal liquid, purifying the product by repeating the treatment with acidulated water, carbonate of sodium, and ether; decolourising; neutralising with hydrochloric acid, and recrystallising.

Characters. - In almost colourless acicular crystals or crystalline powder. The solution in water has a bitter taste, and produces on the tongue a tingling sensation followed by numbness.

Solubility. - It is readily soluble in water, alcohol, and ether.

Reactions. - Its solution gives a yellow precipitate with chloride of gold; and a white precipitate with carbonate of ammonium, soluble in excess of the reagent. It dissolves without colour in cold concentrated acids, but chars with hot sulphuric acid. The solution yields little or no cloudiness with chloride of barium or oxalate of ammonium. Ignited in the air it burns without residue.

Dose. - 1/5 to 1 grain.

Preparation. B.P.

Lamellae Cocainae. Discs of cocaine (each contains 1/200th grain of hydro-chlorate of cocaine, p. 515).

Action. - Cocaine is a powerful local anaesthetic. When applied to the tongue it destroys both taste and tactile sensibility, so that salt and sugar cannot be distinguished, nor the prick of a pin felt. In the eye it causes local anaesthesia along with dilatation of the pupil, paralysis of accommodation, slight lacrimation, and enlargement of the palpebral fissure.1 When injected into the back of the orbit it causes protrusion of the eyeball. Its effects appear to be due to stimulation of the peripheral ends of the sympathetic (vide p. 226). Subcutaneous injection also produces local anaesthesia at the point of application, so that subsequent irritation at that spot produces no sensation in man and no reflex action in animals. When taken internally it appears to have, in small doses, a stimulant, and, in large doses, a paralysing action on the nerve-centres somewhat like that of caffeine. It affects first the cerebral hemispheres, next the medulla, and afterwards the spinal cord. In small doses it is said to lessen fatigue, and enable the Indians in Peru to make long marches; and a similar result has been obtained in trials upon soldiers in Germany. Larger doses cause fulness in the head, weariness, slight deafness, loss of memory, and inability to control ideas. It appears sometimes to cause restlessness, singing in the ears, giddiness, headache, and delirium.

In animals large doses appear to affect specially the semicircular canals, possibly by an anaesthetic action upon the nerves connected with them. This is shown by constant movement of the head in mammals, disturbances of equilibrium, loss of co-ordination, and rotatory convulsions and opisthotonos. The convulsions are of cerebral origin (p. 188), and cease when the spinal cord is divided. The motor columns of the spinal cord appear to be unaffected, but the sensory columns are paralysed. In its action on respiration and circulation cocaine, to a certain extent, resembles atropine, and it does so also in its action on the pupils, intestinal movements, and salivary and sweat glands. The respiration is greatly increased at first, afterwards diminished, and death occurs from respiratory paralysis. Small doses quicken the pulse and raise the blood-pressure. Large doses slow the pulse and lower the blood-pressure. The quickness of the pulse appears to be due to paralysis of the vagus, and the action of cocaine on both pulse and blood-pressure is very like that of atropine. Small doses increase, large ones paralyse, the intestinal movements. The secretion of saliva and sweat is diminished. The urine does not appear to be affected. The temperature is generally raised. Uses. - The expectations of the practical utility of cocaine, founded on a knowledge of its physiological action, which Rossbachl expressed have been completely fulfilled, and it now bids fair to replace as a local anaesthetic the use of chloroform in many minor operations. Its local anaesthetic action was first observed by Niemann. Its actual introduction into practice we owe to Koller. A 4 per cent. solution dropped into the eye is sufficient to produce local anaesthesia, so that operations for cataract or squint can be readily performed, and foreign bodies extracted from the eye under its influence.2 A 20 per cent. solution applied once or twice to the nasal mucous membrane at intervals of three or four minutes causes such complete anaesthesia that the application of the galvano-cautery is not felt. A similar effect is produced on the soft palate and larynx, and the solution may be applied to facilitate the use of the laryngoscope and lessen pain and spasm in operations on the larynx. It has been applied with benefit to the interior of the nose in acute coryza, nasal polypus, and hay fever. It is useful in producing local anaesthesia of the uterus and rectum in operations on these parts; in vaginismus and in pruritus of the anus and vulva. Internally cocaine or coca is useful as a tonic, especially in debility with nervousness, and in mental diseases accompanied by depression. It may be given in the form of the fluid extract either alone or with a glass of wine. A non-officinal wine made from the leaves is also a useful tonic.

1 Jessop, Practitioner, January 1885.

1 Nothnagel and Rossbach, Arzneimittellehre, 5th edition. 2 In consequence of the readiness with which solutions of cocaine undergo decomposition, it is best to add a trace of boric acid (1/2 per cent.) to them.