Psicaine

PSICAINE, Psicainum, the primary tartaric salt of one of the isomers of cocaine, obtained in 1924 by Willstätter (R. Willstätter) and recommended by him for use as a local anesthetic. The chemical formula of psicaine is C₁₇H₂₁NO₄·C₄H₆O₆. Microscopically it is a fine crystalline powder; it dissolves in 4 parts of water, with more difficulty in alcohol; aqueous solutions of P. rotate the plane of polarization to the right and are of acid reaction. Solutions of P. are bitter in taste and cause prolonged anesthesia of the tongue. When solutions are boiled for an hour, P. does not change, which makes it possible to sterilize solutions for subcutaneous injection. During storage, solutions of P. decompose within 1-2 days and lose their anesthetic properties. Gottlieb (R. Gottlieb) noted that the toxicity of P. when administered subcutaneously is half that of cocaine, but when administered intravenously, P. causes convulsions, collapse, and death in the same doses as cocaine. Gottlieb explained the lower toxicity of subcutaneously injected P. by the more rapid dissolution of the P. molecule in the body at the site of injection. The same reason accounts for the more rapid disappearance of poisoning symptoms from P. than from cocaine. Otolaryngologists note that the effect of P. in medical use occurs more quickly and from less concentrated solutions than with cocaine, so that instead of a 10% solution of cocaine, a 5% solution of P. is sufficient, and instead of a 20% solution of cocaine, a 10% solution of psicaine is used. Voelcker recommends using P. in solutions of ¹/₆-¹/₄% for anesthesia of the urethral mucosa or bladder; after 5 minutes of exposure to 10-100 cm³ of such a solution, complete local anesthesia occurred. The anesthetic power of subcutaneously injected P. can be increased by adding potassium sulfate to the solution; adding phenol enhances the effect of P. in surface anesthesia; by adding adrenaline, the duration of anesthesia from psicaine can be increased. Gottlieb indicated the vasodilating effect of P.; Schibashi confirms the vasodilating effect of P. solutions in cases of significant concentration; however, if P. solutions are of very weak concentration or, conversely, very concentrated, then the blood vessels again constrict under the action of such solutions. Heart rate from small doses of P. slows down, the diastolic phase increases; from large doses, heart contractions weaken, arrhythmia occurs, and death occurs with signs of cardiac arrest in diastole, with the myocardium noted to retain its resistance. P. relaxes the rabbit's small intestine, but at certain concentrations of P. solutions it can also excite them; the movement and tone of the rabbit's uterus are enhanced by weak concentrations of P. solutions, while stronger concentrations relax them. P. does not cause pupil dilation; rarely, transiently, and insignificantly changes the superficial layer of the corneal membrane; in this case, 10% solutions of P. act as a 5% or 4% solution of cocaine. P. has little effect on intraocular pressure, raising it very slightly. 5% and stronger solutions of P. cause temporary spasmodic closure of the eyelids. No widening of the palpebral fissure occurs from P. The edges of the eyelids and their mucous membrane become slightly hyperemic. P. does not cause euphoria at all, while its effect on the psyche is essentially very similar to that of cocaine (Graf). Since no habit is formed to P. in its medical use and it is less toxic when administered subcutaneously, it is strongly recommended to use it for local anesthesia instead of cocaine. The therapeutic value of P., despite this, is still small. The reason for this is that in some cases the toxicity of P. is no less than that of cocaine, and that P. more strongly stimulates the motor sphere than cocaine; on the other hand, tropocaine, tutocaine, and novocaine, with their high anesthetic properties, appear even safer in medical use. P. is used for subcutaneous anesthesia in doses up to 0.03; as eye and ear drops in 1-2% solutions; in urological practice—¹/_{6-¹/4-¹/2% solutions.}