The protocetatic acid is an acid that, according to Hessen, exists in the lichen of Iceland and that by hydrolysis is split into cetrárico acid and fumaric acid. According to Hesse, cetrárico acid does not exist in this lichen, but it results from the decomposition of the protocetrárico. According to Simon, there are two acids already formed in the lichen of Iceland.
Protocetrárico is the active principle of the lichen of Iceland and to which the antiemetic action of its tincture must be attributed. This effect is due to the exaggeration of continued intestinal peristalsis from the cardia to the pylorus. The proteictrárico acid exerts a stimulating action on the neumogastric nerve, diminishing, on the contrary, the tone of the sympathetic nerve. The emetic action is exercised, then, by a complex mechanism, but mainly central nervous. The effects of protocetrárico acid studied experimentally by Robin and Brissemoret is not accompanied only by some light cramps in certain individuals. At a strong dose the medicine is given as purgative, exaggerating intestinal peristalsis. Protocetric acid has been prescribed against vomiting of migraine, intoxication and tuberculosis. It is also advised in hysterics and those who subscribe to chloroformic anesthesia. It also has good effects on the incoerc vomiting of pregnant women. It is prescribed in alcoholic solution at a dose of XX to XXX drops at a time, and may reach, depending on the case, up to CC per day.
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