This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol2", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
This may be prepared in the following manner. To an alcoholic extract of the root add water acidulated with sulphuric acid, by which the native salt of aconitia is decomposed, and a readily soluble sulphate is produced. Filter the liquid, and add solution of ammonia, which separates and precipitates the alkaloid with impurities. From the precipitate extract the aconitia by means of ether, and allow the ethereal solution to evaporate. For details of the procedure, the reader is referred to the U. S. Dispensatory.
When quite pure, aconitia is in the form of a white powder; but, as in the shops, it is often slightly coloured. According to M. Hottot, it is in this state a hydrate, which melts when gently heated, loses 26 per cent. of its weight of water, and, on cooling, assumes a transparent resinous appearance, and has an amber colour. Obtained by the slow evaporation of its alcoholic or ethereal solution, it is transparent like glass. The alkaloid is uncrystallizable. it is inodorous, of a bitter taste, and has the same singular acrimony as the herb or root. it is unalterable in the air, not volatilizable, decomposed at a high temperature, sparingly soluble in water, readily soluble in alcohol and ether, and capable of neutralizing the acids, with which it forms uncrystallizable salts. it consists of nitrogen, carbon, hydrogen, and oxygen.
Aconitia acts on the system in the same manner as the tincture, but with greater energy. M. E. Hottot gives the following account of its effects, as evinced in himself and two other persons upon whom he experimented. The quantity taken was three milligrammes, or about the twenty-second part of a grain. Almost immediately after it is taken, an acrid sensation attended with heat spreads over the whole mucous membrane of the mouth, extending quickly to the throat, and ultimately to the stomach. This sensation becomes more and more lively, the heat increases to burning, and a feeling of numbness follows in the lips, tongue, and pharynx, while there is often at the same time a copious flow of saliva. Some general uneasiness is now experienced, with weakness, heaviness of head, then nausea, frequent yawnings, a sense of oppression, and marked muscular debility. The pulse is slightly elevated, tho skin is moist, and formication is felt in different parts of the body, especially the face and limbs. After a time increased depression comes on, with headache and often lancinating pains in the face, especially along the course of the nerves. The muscular weakness increases, formication becomes more manifest, the limbs feel as if bruised, the face is tense and swollen, the pulse falls, respiration is difficult, there is a painful burning in the throat, copious sweats occur, a general weakness is felt with a difficulty in holding objects, the least effort is exhausting, the respiration is slow and deep, the pulse notably lowered, the mind remains clear, a tendency to sleep is rare, and the pupils are dilated, but less than by atropia. These symptoms continue from ten to sixteen hours, and then gradually subside. (Ann. de Thérap., 1864, p. 44.) One-fiftieth of a grain killed a sparrow; and the same quantity is said to have proved dangerous and nearly fatal, in the case of an old woman. in an instance recorded by Dr. Golding Bird, two and a half grains produced poisonous symptoms; but the patient vomited and was saved. When rubbed on the skin in the form of an ointment, or in alcoholic solution, it occasions violent heat, tingling, and numbness, which may continue from two or three to eighteen hours. "A minute portion of an ointment, composed of a grain of the alkaloid to two drachms of lard, applied to the eye, causes almost insupportable heat and tingling, and contraction of the pupil." (Pereira, Mat. Med., 3d ed., p. 2176.) There would seem to be no real occasion for aconitia as a distinct preparation; for the tincture of the root is capable of producing all the desired effects both internal and external. it has, however, been considerably employed, especially in neuralgic, gouty, and rheumatic affections. it has been recommended also in pneumonia, hooping-cough, puerperal fever and purulent infection, amenorrhoea with congestion of the uterus, various irritating cutaneous diseases, as prurigo, lichen, and urticaria, and in different nervous affections, as epilepsy, chorea, and tetanus, and in the last-mentioned disease has been given with some success. From one-hundredth to cine-fiftieth of a grain may be given for a dose. it is, however, more used externally than internally, and is especially applicable, in this way, to neuralgic, rheumatic, and gouty disease. it may be employed in alcoholic solution or ointment; in the former case, one grain being dissolved in a fluidrachm of alcohol; in the latter, two grains being rubbed, first with six drops of alcohol, and then with a drachm of lard. The proportion of the alkaloid, if found necessary upon trial, may be doubled or quadrupled. The preparations are to be applied by friction. The same rule is necessary in relation to the continuance of the friction, and the same caution in reference to the surface of application, as in the employment of the tincture of the root. Aconitia has been used in subcutaneous injection, for which the commencing dose may vary from the 1/120 to the 1/50 of a grain, and should not exceed the latter quantity.
The British Pharmacopoeia directs an Ointment of Aconitia (Unguen-tum Aconitia, Br.), made by first dissolving eight grains of the alkaloid in half a fluidrachm of rectified spirit, and then mixing the solution thoroughly with an avoirdupois ounce of lard.