Salol

SALOL, Salolum, phenyl salicylate, Phenylum salicyl., C₆H₄(OH)COOC₆H₅ [1,2] (State Pharmacopoeia), is a white crystalline powder with a faint aromatic odor and a characteristic taste. It is almost insoluble in water, dissolves in 10 parts of alcohol, and is easily soluble in chloroform and very easily in ether. It melts at about 42° after drying over sulfuric acid. An alcoholic solution of salol takes on a violet coloration upon the addition of a dilute solution of ferric chloride. Salol should not color moist blue litmus paper red (salicylic acid), and after shaking 1 part with 50 parts of water, it should yield a colorless filtrate that does not change upon the addition of a dilute solution of ferric chloride (sodium salicylate, salicylic acid, phenol), nor should it give a reaction for chlorides or sulfates.

Proposed by Nencki in 1886 as a preparation of salicylic acid and phenol, it is devoid of the unpleasant taste and irritating properties of the latter and is less toxic. When taken per os, in view of its almost complete insolubility in the stomach contents, it passes through the stomach without irritating it and enters the intestine in an unchanged state. In the intestine, under the influence of alkalis, pancreatic enzymes, and bacteria, it decomposes, yielding 40% phenol and 60% salicylic acid. Saponification occurs gradually and relatively slowly, and the phenol and salicylic acid obtained from the decomposition of salol are rapidly absorbed and then excreted in the urine, which, after taking large doses, acquires the character of phenol urine, becoming dark green (especially on the surface and upon standing), which is caused by the formation of darkly colored oxidation products of phenol. Due to the slowness of the decomposition of salol in the intestine, as well as the rapidity of the absorption of the decomposition products, the irritating effect of salol on the intestine is not sharply pronounced. The decomposition of salol in the intestine is subject to individual variations, and sometimes a certain amount of undecomposed salol can be detected in the feces. With prolonged use of salol, the formation of "salol stones" in the intestine is possible, which can even cause symptoms of acute intestinal obstruction (pain, vomiting). When introducing salol into practice, it was intended for its disinfecting effect on the intestine and was recommended for a number of intestinal infections (typhoid fever, tuberculosis, cholera, especially infantile diarrhea); however, in view of the rapid absorption of the decomposition products of salol, its disinfecting effect on the intestine is not particularly great. It should be noted that the saponification of salol under the influence of alkalis and pancreatic enzymes proceeds so slowly that it is inferior in its effect on putrefactive bacteria in in vitro experiments to sodium salicylate and bismuth subnitrate (Sollmann). Some decomposition of salol also occurs under the influence of breast milk, which is why gastric symptoms are sometimes observed when it is used in infants. According to studies by Kumagawa, the content of indican in the urine (a measure of putrefactive processes in the intestine) does not fall when taking salol, just as the number of bacteria in the feces remains extremely high. According to the majority of authors, the use of salol as an antiseptic agent for the urinary tract, especially the bladder, is of significantly greater importance than for intestinal disinfection. Unlike urotropin, which acts only in acidic urine, the reaction of the latter does not hinder the action of salol. Some authors (Sollmann), however, consider salol to be a weakly acting agent in this case as well. As an antirheumatic agent, salol acts more weakly and less reliably than sodium salicylate. At the same time, its dosage must be more limited in view of the possibility of phenol poisoning. On the other hand, when used in moderate doses, in view of the above-mentioned slowness of the decomposition of salol, the side effects observed when taking salicylates occur less easily. The use of salol as an external wound antiseptic, according to Cushny and Sollmann, is hardly rational, since wound discharge does not saponify salol, which decomposes very slowly there only under the influence of bacteria; on the other hand, according to older studies (Sahli and others), the decomposition of salol in a weakly alkaline medium and with the addition of tissue products occurs energetically. Salol was proposed as a means of determining the motor function of the stomach (Ewald). In this case, the time interval between taking salol (with a test breakfast) and the appearance of a reaction for salicylic acid in the urine (coloration from ferric chloride) is measured. If the reaction occurs later than 75 minutes, the motor function of the stomach is reduced. According to Cushny, this test is not reliable, since a certain, albeit small, part of salol is decomposed in the stomach, and the reaction in the urine may appear before the food chyme and salol pass into the intestine. Due to the fact that salol is almost insoluble in the stomach, it is sometimes used to coat pills if it is desired that they pass through the stomach in an unchanged state. The layer of salol on the pills must be sufficiently thick. When taking salol in excessively large doses, poisoning has been observed, the symptoms of which correspond to phenol poisoning (especially kidney damage). Side effects sometimes observed with moderate doses (e.g., hearing impairment) are explained by the action of salicylic acid. When prescribing salol in the form of powders or tablets, it is useful to mix it with indifferent substances (e.g., starch) to avoid the sticking of salol particles and the formation of stones. For children, it is sometimes prescribed in the form of an emulsion of salol in oil. Doses for adults: 0.3–0.5–1.0 several times a day; for articular rheumatism, 1.0 several (5–6) times a day. Externally in ointments (5%).

A. Likhachev.