This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol1", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
This alkaloid is extracted in the same manner as strychnia, and accompanies it in the first steps of the process, but is in great measure separated on the crystallization of the latter from the alcoholic solution, remaining behind in the mother liquors in consequence of its much greater solubility in alcohol when cold. Still, it is with difficulty entirely separated from strychnia, and is very apt to contain it as existing in commerce. It should be procured in the state of crystals. It is bitter, but less so than strychnia, and much more soluble in water and cold alcohol. It is reddened by nitric acid. Its claims to be considered as a distinct principle have been denied; and Dr. Fuss supposes it to be a compound of strychnia and resin. It forms, however, distinct salts with the acids, which are for the most part soluble and crystallizable.
From experiments of Magendie, Andral, and others, brucia is believed to be identical in its effects with strychnia, only much weaker. M. Le-pelletier, however, who had ample opportunities of noting its effects in the hospital practice of M. Bricheteau, though he considers its physiological action analogous to that of the stronger alkaloid, has yet found it to be in some respects peculiar. Thus, the fingers and great toe are rapidly extended and flexed, sometimes even producing a friction sound in the articular surfaces, but are never affected with that tetanic rigidity so characteristic of the action of strychnia. Moreover, the muscles of the jaws, pharynx, and oesophagus, which participate in the spasmodic effects of the latter principle, remain almost always unaffected under the influence of brucia. On the organs of generation, however, brucia acts with considerable energy. But, according to M. Lepelletier, the great advantage of brucia is its comparative safety; and, if it be true that it does not produce the tetanic rigidity, as he asserts, the danger of as. phyxia, at least from the immovability of the respiratory muscles, is avoided. M. Bricheteau, though he has employed brucia for a very long time, has never known serious consequences to result. It may be used for the same purposes as strychnia, its great advantage being, according to the author just cited, its comparative safety. He considers its influence over the generative organs, in connection with its entire harmlessness, a peculiar recommendation. But, as it is often combined with strychnia, it is indispensable, in order to obtain due results, that attention should be paid to its purity, and that it should be employed only when in the crystalline state. (Ann. de Therop., 1852. p. 50, etc).
Statements vary as to the comparative strength of brucia. Andral considers it as having only one-twenty-fourth of the strength of pure strychnia, Magendie the one-twelfth. M. Lepelletier gives the commencing dose of it, when quite pure, at two centigrammes (about one-third of a troy grain), to be increased progressively to five, ten, twenty centigrammes (about three grains troy), or even more, if necessary to obtain its physiological effect. (Ibid., p. 62).