This section is from the book "Dental Medicine. A Manual Of Dental Materia Medica And Therapeutics", by Ferdinand J. S. Gorgas. Also available from Amazon: Dental Medicine.
Cocaine is the alkaloid obtained from the leaves of the Erythroxylon Coca, a shrub indigenous to certain parts of
South America, as Peru and Chili. The leaves resemble those of Chinese tea, and in the preparation of the alkaloid it is necessary that they should be of the best quality, which depends upon their being gathered at a proper time, carefully dried and not injured by age or by exposure to the air, as moisture deprives them of all value. Erythroxylon Coca is different from chocolate or Theobroma Cacao. Pure cocaine is in the form of transparent prisms, without smell, bitter to the taste, soluble in seven hundred parts of cold water, more soluble in alcohol, and entirely soluble in ether. The solution has an alkaline reaction, and, when applied to the tongue, it imparts a bitter taste, and a certain insensibility, followed by a slight sensation of cold, recalling the effect of ether spray upon the epidermis. Heated to 2080 F., the cocaine becomes liquid, and under the influence of cold, it becomes a transparent mass, which gradually assumes a crystalline form. If it be exposed to a higher heat than 2080 F., cocaine changes its color and decomposes. It is inflammable, and burns with a brilliant flame, leaving an ash. It forms soluble salts with acids (its hydrochlorate is one of the best), and all these salts are more bitter than the alkaloid. It is a compound of carbon, hydrogen, nitrogen and oxygen. The chemical composition of the alkaloid is C17H21No4; its reaction is strongly alkaline.
The hydrochlorate of cocaine is generally employed in surgery, and is in the form of a white crystalline powder, which is sparingly soluble in water, but readily soluble in alcohol, ether, oil and vaseline. At first a 2 per cent. solution was used, but subsequently it was increased to four, five, ten and twenty per cent.
Dr. Niemann, of Goslar, as early as 1860, noted the fact that cocaine, when applied to the tongue, produced local anaesthesia, but his investigations, as well as those of others at a later period, appear to have been forgotten, until 1884, when Dr. Koller, of Vienna, demonstrated the action of cocaine, in solution, on the eye.
Locally applied to the mucous membrane, cocaine acts as an anaesthetic, the blanching of the membrane being followed by marked congestion. It has a powerful action on the eye on account of the delicacy of the conjunctiva, which it readily penetrates, and thus paralyzes the peripheral nerve-endings. The anaesthesia is produced in from one to five minutes according to the strength of the solution used, and is accompanied by marked dilatation of the pupil. Applied to the peripheral sensory nerves it paralyzes them; its action is manifested first upon the sensitive fibres and then upon the motor fibres. Poisonous doses of cocaine cause convulsions of cerebral origin, both clonic and tetanic. Taken internally cocaine stimulates the muscles, increasing muscular power temporarily, especially after starvation or fatigue. It acts as a stimulant to the heart and circulation in moderate doses, and also as a powerful respiratory stimulant, and in poisonous doses it destroys life by failure of the respiration with exhaustion from the convulsions. Cocaine increases the bodily temperature if given in large doses, due to an increase of heat-production; but in moderate doses it has no such effect.
Cocaine is eliminated by the kidneys, but is chiefly dissipated by oxidation in the body.
Cocaine is an efficient local anaesthetic in all cases where it can come in contact with the nerve filaments in sufficient concentration. It is also employed in some forms of insanity, melancholia, neurasthenia, gastralgia and in wasting diseases, pruritic skin affections and hoarseness. The leaves in cigarettes have relieved hay fever and throat affections. Cocaine is employed as a local anaesthetic and local anodyne in all painful affections of the eye, the operation for cataract, etc., but the evidence as to its reliability in such deep operations as iridectomy, squint, etc., is conflicting. (There are, however, cases reported by Dr. Konigstein of even the surfaces of the eyelids entirely losing their sensitiveness when hydrochlorate of cocaine was applied in solid form.) It is also employed in painful affections of the pharynx and larynx, or of any other excitable mucous membrane or of nerve tissue. Prof. Engle reports a case of trigeminal neuralgia successfully treated by hypodermic injections of the hydrochlorate of cocaine. Dr. Wagner, of Vienna, basing a theory upon the established principle that fluids move from the positive to the negative pole in a galvanic current, saturated the positive electrode with a strong cocaine solution, applied it to the skin and applied the negative pole a short distance from the positive, and found that incisions could be made without producing any pain. (See Cataphoresis.)
Cocaine is locally applied in stomatitis before cauterizing the affected area of membrane, also in soreness and tenderness of the gums, in pharyngitis, and in coryza and hay fever, in the form of a powder combined with morphine and bismuth, which is snuffed into the nostrils; also in minor surgery, such as amputation of the fingers, etc., etc. Schleich's infiltration anaesthesia consists in injecting into the skin, as superficially as possible, a solution of common salt, cocaine, and morphine to produce local anaesthesia, and thereby pressure on the nerve-filaments, which are also depressed by the cold liquid coming in contact with them; and the local anemia so caused assists in destroying sensation. Whereas cocaine is soluble in fats, its salts are not, hence cocaine itself should only be used in anaesthetic salves or ointments. Internally administered, cocaine or the fluid extract of coca is of service in low fevers as a supportive and stimulant; in the vomiting of pregnancy, and other forms of severe emesis, as it depresses the gastric sensory nerves, thus decreasing the irritability of the stomach. It is also employed for the opium habit, but if given largely may induce the cocaine habit. The cocaine habit is more liable to occur among patients who are informed of the nature of the remedy used and especially is this the case when it is employed internally for medicinal purposes. Individual susceptibility to the toxic influence of cocaine is a complication of sufficiently frequent occurrence to surround the use of the drug with due care and caution; but it is not a contra indication to its employment as an anaesthetic.