Antifebrin

ANTIFEBRIN, Antifebrinum, compositionally Acetanilidum, is obtained synthetically from aniline and acetic acid: C₆H₅.NH₂ + CH₃.COOH = H₂O + C₆H₅.NH(COCH₃), by substituting the hydrogen of the amino group in aniline with the radical of acetic acid. Antifebrin is a shiny, crystalline powder without odor, with a slightly burning taste; it dissolves in 230 parts of cold and 22 parts of boiling water, and in 1 part of hot alcohol. Aqueous solutions of antifebrin must have a neutral reaction. It melts at a temperature of 113-114°. Antifebrin irritates the gastric mucosa less than antipyrine; it is absorbed rapidly and lowers body temperature within an hour. The mechanism of the antipyretic action of antifebrin is partly similar to that of antipyrine and is explained by the action of antifebrin on the heat-regulating centers and the dilation of peripheral vessels; with antifebrin, one must also take into account its direct action on peripheral vessels and, furthermore, changes in the blood that sharply limit the processes of oxidation and heat production. The changes in the blood consist of pronounced methemoglobinemia, reaching approximately 33% in humans and sometimes even 62% in experimental animals, yet without causing the death of the animal. Ellinger attributes the appearance of methemoglobin in the blood to the fact that antifebrin plays a role similar to a catalyst here. In doses of 0.5 and higher, antifebrin often causes symptoms of poisoning: cyanosis of the lips, nose, chin, ear conchas, and eyelid skin; general weakness, dizziness, nausea, vomiting, and sometimes diarrhea; pallor of the skin, chills, profuse sweating, drop in temperature, weakening and acceleration of the heartbeat, rapid followed by slowed and weakened respiration, dulling of sensitivity, tremors, convulsions, pupil dilation, collapse, and sometimes death. The toxicity of antifebrin depends on its constituent part, aniline. Treatment for poisoning: induce vomiting in the poisoned person, wash out the stomach with cold water; inject caffeine or camphor under the skin; internally for convulsions—chloral hydrate, sodium bromide; warming the body, skin irritation. Chronic use of antifebrin leads to severe cachexia. The toxicity of antifebrin increases if it is prescribed simultaneously with caffeine. Antifebrin is eliminated from the body, having broken down within it, through the kidneys in the form of paired compounds of acetylated para-aminophenol with sulfuric or glucuronic acids. In therapy, antifebrin was important as an antipyretic and analgesic in doses not exceeding 0.5, but it is now hardly used due to its toxic properties. Detection in forensic cases. When examining viscera, vomit, and other excretions, antifebrin passes into chloroform from an acidic unfiltered solution (see Poisons-Isolation); upon evaporation of the chloroform extract, a crystalline residue is obtained. One part of the crystals is heated with concentrated HCl (0.5-1 minute) until dissolved; a few drops of carbolic acid solution and chlorinated lime solution are added to the solution: a dirty-violet coloration proves the presence of antifebrin (reaction of aniline with chlorinated lime-see Aniline); the liquid is made alkaline with ammonia: a blue coloration (indophenol reaction). Another part of the residue is heated with an alcoholic solution of sodium hydroxide and a few drops of chloroform: a characteristic unpleasant odor of isonitrile is felt (distinction from phenacetin). For the quantitative determination of antifebrin, it is boiled with concentrated HCl, and the resulting aniline is precipitated by titration with bromine solution, and the excess bromine is determined (see Aniline-Detection in forensic cases). V. Nikolayev, A. Stepanov.