A valuable preventive to this absorption is found in the application of a constricting band or tourniquet to impede the return circulation and allow the washing out of much of the drug before the obstruction is removed. It is evident that no method has yet been devised whereby the use of cocaine is rendered safe and it is for this reason that chemists throughout the world have sought to produce either a new anesthetic drug or to evolve a drug synthetically, from cocaine, minus its toxicity. This has been done, but cocaine still has its adherents because of its superior qualities.
Quinine and urea hydrochloride is one of the new substitutes which has found much favor. Among the synthetic derivatives may be mentioned alypin, novocaine, stovaine, betaeucaine, tropacocaine, anesthesin, subcutin and many others. Each of these has its advocates and all of them have some advantage over cocaine; they have disadvantages as well, which, however, in the hands of skilled operators, may be overcome.
Quinine and Urea Hydrochloride. Among the quinine salts and combinations, the above has found most favor. It consists of a molecule of quinine hydrochloride and one of urea. It occurs as a fine crystalline powder and is readily soluble in water, forming an acid solution.
This substance is one of the most recent and best substitutes for cocaine, being capable of a wide range of usefulness and practically devoid of any toxicity. It causes redness on being injected and, in strong solutions, may delay healing considerably, this constituting the main disadvantage to its use. After the use of this anesthetic, primary union is not usual.
In a one per cent. solution, anesthesia is accomplished by any of the methods already described. Weaker solutions require a more perfect technic, and are therefore not generally employed. They, however, are indicated where it is imperative to secure primary union and when for some reason no other local anesthetic is available. The scar formation which almost always follows the use of this anesthetic would indicate that some other drug be employed in operations about the face and neck. This anesthetic is preferred by many because of its safety in large quantities and because of the length of insensibility following the injection of solutions of from 1 per cent. to 2 per cent. strength.
Notwithstanding knowledge of the facts above enumerated as to the difficulty of primary union and the likelihood of scar formation in connection with the use of urea and urea-hydrochloride for purposes of local anesthesia, this drug is still considered a most valuable and useful one for providing local anesthesia for operative purposes.
Novocaine. This drug is one-seventh as toxic as cocaine but is also weaker in action. It does not cause vascular constriction but has a preliminary vasodilator action. Like quinine, it has a decidedly irritating action when injected. It has a decidedly toxic effect when used in stronger solutions than 2 per cent. and causes tonic and clonic spasm. In a 1 per cent. solution it is probably safest and best as an anesthetic and one-half ounce of such a solution may be injected without fear of unpleasant consequences.
Its dose is said to be about seven grains, but this may often be the cause of alarming symptoms, and half of this quantity would perhaps be a safe limit. The duration of anesthesias of fairly strong solutions is about fifteen minutes; the action is more prolonged if used with adrenalin.
Various combinations of drugs besides adrenalin are employed with novocaine. Fischer recommends its use with thymol, but even so, it is not efficient for a longer period than twenty or twenty-five minutes.
Novocaine is frequently used in alcoholic solutions for injection in neuralgic subjects. The commercial tablet of novocaine and adrenalin is convenient for office use.