Besides rendering the superficial structures of the eye anæsthetic, it is a mydriatic, and produces paralysis of the accommodation, which passes off sooner than the dilatation of the pupil; this does not at longest last more than twelve hours. The sensitiveness of the iris is less affected than that of the surface of the eye. The great excellence of cocaine consists in the limitation of its action to the tissues to which it is applied. No doubt, other symptoms at a distance do result from the external application of the anæsthetic, but they are, for the most part, insignificant and free from dangerous consequences. In some measure cocaine may be compared with curare. The one agent paralyses the termination of the sensory nerves, whilst the other paralyses the termination of the motor nerves. Cocaine would seem to act in a manner the reverse of aconite. When applied to a mucous membrane, it has probably a constricting action on the vessels, produces a blanching of the part, and simultaneously a deadening of the nervous excitability which passes into a complete state of anæsthesia; its effect, however, does not sink deeply into the adjacent tissues, nor does it last long. This surface application is sufficient to render painless the use of a caustic, the passage of catheters and lithotrites, or the performance of operations which do not involve the more deeply-seated tissues. Such operations as the opening of abscesses and buboes, the removal of small tumours, require the surface anæsthesia to be supplemented by two or more hypodermic injections, of a quarter of a grain in each, of the hydrochlorate in close contiguity to the part to be operated on. Injected hypodermically, the aqueous solutions of its salts deaden sensibility around the puncture, so that the deep prick of a pin is not felt—the surrounding part is reddened, but after thirty minutes it resumes its normal condition; injected locally, is more useful than morphine in relieving sciatica. Although solutions of it are little absorbed by the skin—even a chloroform solution is scarcely at all absorbed—yet the application of an ointment of the pure alkaloid, made with lard, or an oily solution of it, to a surface will remove the pain of inflammation, as in eczema or erysipelas, or the pain of facial neuralgia or shingles, and the irritation of urticaria or pruritus. Burns and scalds should first be brushed over with a 4 per cent. aqueous solution of the hydrochlorate, and the pure alkaloid combined with carron oil (Linimentum Calcis), petroleum cerate, or boric acid ointment, afterwards applied on cotton wool or lint. Combined with boric acid ointment, also, it may be used for fissured nipples, or for these and stings and bites of insects an aqueous solution may be applied. The irritability of inflamed mucous surfaces, as in hay-fever, influenza, coryza, bronchitis, spasmodic asthma, laryngitis, and pharyngitis, is much relieved by the spray of a watery solution of a cocaine salt. In obstetrics, its local application relieves the pain of the dilating os uteri, and diminishes the sensibility of the perinæum whilst being dilated in first labours; rents of the perinæum may be stitched up almost painlessly under its action, and under its influence many minor gynæcological operations are much facilitated by the ability to insert needles and make small incisions without pain. The spasmodic and painful affections of the vagina, causing dyspareunia and vaginismus, may be minimised by vaginal injections of a quarter of a grain of cocaine in 1 per cent. oily solutions. In dentistry, it is useful in toothache; it deadens the sensibility of exposed pulp. The pure alkaloid is preferable to the salts for this purpose, because, being only slightly soluble in water, it is less liable to be washed away by the saliva. If a little be inserted in the cavity of a carious tooth and covered with a plug of mastic solution, all pain is obtunded for a considerable time. A strong solution in oil of cloves is also useful. In preparing the cavity, previous to filling, the sensitiveness of the dentine is more effectively treated by using a salt of cocaine—either the hydrochlorate or citrate; the latter has been recommended, as it can be formed into a pellet with the fingers and pressed into the cavity, but it is not so rich in true alkaloid as the hydrochlorate; yet, either of these is absorbed more quickly than the alkaloid itself, which, as before said, is more suitable for plugging a cavity for some length of time. Before using arsenical paste to destroy the nerve when exposed, if about a quarter of a grain of a cocaine salt be inserted into the cavity, after partially clearing, it will anæsthetize the pulp in about five minutes, and enable the operator thoroughly to open the cavity and expose the pulp directly to the action of the arsenical paste without pain to the patient. In extraction, if a dose be hypodermically injected into the gum on each side at the base of the tooth, after waiting about five minutes this may be done almost painlessly, and, if a 50 per cent. aqueous solution of the hydrochlorate be painted on the surrounding gum, the first pain of inserting the forceps is annulled. The eye, ear, throat, mouth, tongue, pharynx, nose, larynx, trachea, urethra, vagina, os uteri, anus, rectum, and, in fact, the whole mucous membrane, as well as cut surfaces and open sores, are affected by it, but the true skin is less so.
Solutions of hydrochlorate of cocaine have been employed topically in excision of the tonsils, cauterizing the turbinated tissue of the nose, painting chancres previous to the application of nitric acid or other caustics, opening abscesses, removing polypi, and many cases of iridectomy and operation for cataract, squint, and the removal of foreign bodies from the eye. For the eye an aqueous solution of the hydrochlorate of cocaine of mostly 2, but sometimes 4, per cent. is used, and for other purposes from 4 to 20 or even 50 per cent.; of the weaker solutions it is necessary to repeat the application three to five times, at intervals of three to five minutes. No operation should be commenced within at least ten minutes of the first application. Injurious effects, either local or constitutional, rarely follow its use. Its action commences in three minutes, increases from ten to twenty minutes, and mostly disappears within half an hour. The anæsthesia may be prolonged by applying an Esmarch’s bandage round the site of injection.
Uses of Cocaine, and cautions on its employment; a summary of the experiences of fifty-two surgeons in the United States. In minor surgery—is of value in all operations where circulation can be temporarily arrested in order to prevent undue absorption. A fresh solution should be employed, of strength not exceeding 4 per cent. Caution is required when the circulation cannot be controlled. Is of little use as a local anæsthetic in anal work, such as fistula. In genito-urinary surgery must be used with care, as it is in this class of cases that untoward effects have been most marked; the solution should not remain in contact with mucous surface more than a few moments. In gynæcological work it is of limited service, as general anæsthesia is mostly to be preferred. For ophthalmic surgery, Cocaine is the anæsthetic par excellence; in no other department of surgery is its use so widespread and its application so entirely satisfactory. It is suitable for all operations on the eyeball, except iridectomy for acute glaucoma, and enucleation; as it causes dryness of the epithelium it should not be used long prior to operation. Is of great value in nasal, aural, and throat operations.—Th. Gaz. Aug. 1891, 518.
Chloroform and Cocaine Anæsthesia (combined).—Chloroform is given, 1 to 3 drachms, with an Esmarch’s mask, and from ½ to ¾ grain of cocaine, in 3 to 5 per cent. solution, injected into the part. Less chloroform suffices, vomiting is rare, and depression on waking slighter than chloroform alone produces.—L ii./88,220; B.M.J. ii/88,903. Th. Gaz. Sept. 1888, 630; Oct. 686; Dec. 849.
Equal parts of an 8 per cent. solution and liquor atropinæ sulphatis form an effective remedy for all painful and inflamed conditions of the eye; and half a grain of pilocarpine nitrate, added to 1 drachm of a 4 per cent. solution, produces anæsthesia without in the least disturbing the accommodation.—Whitla.
As regards the toxic properties of cocaine, its effects appear to be mild and not cumulative. It causes cessation of respiration,—small doses have an exhilarating effect on the nerve-centres and other parts of the nervous system. In a case of attempted suicide by an apothecary, a dose of 1.5 grammes (23 grains) seemed to have no seriously injurious effect.—Varge’s “Zeitschr.” v.f. 11, 5, p. 222, 1863.
A writer in the British and Colonial Druggist, Feb., 1885, p. 36, thus describes the effect of a full dose:—
“Inasmuch as the writer—whose nervous system is of an almost unfortunate degree of sensitiveness—has taken doses of the hydrochlorate, equivalent, in the aggregate, to no less than 32 grains of cocaine itself within the space of three hours, without (as the present lines sufficiently prove) a fatal result following, this remarkable body cannot fairly be classed among the poisonous alkaloids. Among the chief symptoms induced were increased cerebral activity mounting at intervals into the region of delirium, the latter tendency always subservient to a powerful effort of the will. This continued for five hours, the heart action and breathing being meanwhile slightly increased, but not to any painful extent. At first the muscular powers appeared to be enhanced, heavier weights being lifted without undue stress than is ordinarily the case, while the reflective faculties—as instanced by ability to read and form conclusions upon novel scientific matter—seemed stimulated. An hour after the entire quantity named had been taken, the sensibility of the limbs to external influences—which had gradually diminished from the first—became materially lowered, and neither pinches, pricks, nor slight burns with a heated wire could be felt upon the fleshy portions of the arms or legs. The trunk, however, never lost its sensibility to pain in any marked degree.
“Slight convulsive movements and a sensation of bodily torpor succeeded, giving way about the eighth hour to considerable somnolency. No special desire, or distaste, for food was noticeable, but sleep overcame all other symptoms between ten and eleven hours from the commencement, and continued for thirteen hours afterwards; a slight feeling of dizziness was experienced on waking, but this gradually wore off, and had entirely disappeared twenty-four hours later.”
By physiologists, it had been supposed that cocaine would have properties allied to, if not identical with, caffeine, theme, or theobromine, in the manner that these themselves are allied. But, chemically, cocaine is quite distinct; it is much less soluble in water than caffeine; it is a strong base, which caffeine is not, and its chemical constitution and derivatives are quite distinct from those of caffeine. As a medicine, the coca leaf has been more used in France and America than in England.