146. Aconitum.—Aconite. Monkshood.
The minimum lethal dose of fluidextract should not be greater than 0.00004 mil for each gramme of body weight of guinea-pig.
BOTANICAL CHARACTERISTICS.—Stem 3 to 4 feet high, smooth and erect; leaves nearly sessile, alternate, palmately 5-divided; root-leaves long-petioled; flowers deep violet, irregular, very showy, in racemes; sepals 5, petaloid, the upper one hooded or helmet-shaped; petals 2, concealed.
SOURCE AND VARIETIES.—This genus of poisonous herbs, including a number of species, is found throughout cold, mountainous districts of Europe, in the Himalayas, and in Northwestern North America. It is one of the oldest and commonest plants of the English garden, and is often found in dangerous proximity to horseradish (Royle). Hindu writers mention no less than eighteen different kinds of "bish"—the vernacular for aconite. Ten of these are said to be unfit for medicinal use on account of their extremely poisonous nature. The root (tuber) of A. napellus is the source of the medicinal preparations of this drug. Nepaul aconite is the source of the extremely active alkaloid, pseudaconitine (see below). A. fischeri produces Japanese aconite root. It yields japaconitine, stated to be identical with aconitine.
DESCRIPTION OF DRUG.—Almost napiform, abruptly tapering, from 40 to 100 mm. long, about the thickness of a finger at the top, which is tuberculated; externally dark-brown, wrinkled longitudinally at lower portion, stem scars visible, rootlets usually detached; fracture short, horny or starchy, exhibiting sometimes a spongy or resinous, white, grayish, or brownish tissue; taste at first sweetish, then acrid and tingling, followed by numbness. This peculiar tingling sensation of the tongue is one of the most prominent characteristics upon which the toxicologist depends for the recognition of this drug and its preparations. At the upper portion of the root there of ten projects a lateral branch connecting a second tuber, which is an offspring of the other. A cross-section of the tuber shows a thick bark and a pith often in the form of a star, the two being separated by a nucleus sheath; the cambium, following the outline of the pith, is also 5- to 7-angled, and at the terminal and basal extremities of each ray are found small groups of vascular bundles; these, however, are inclined to follow the whole cambium line.
Powder.—Microscopical elements of: See Part iv, Chap. I, B.
CONSTITUENTS.—The principal constituent is aconitine, C34H47NO11 (0.5 per cent.), forming about one-third the total alkaloid of the root. This is white, usually amorphous, but with difficulty may be obtained in rhombic, tabular crystals; almost insoluble in cold water, soluble in alcohol, ether, and diluted acids. Other related principles exist in the drug combined with aconitic acid (H3C6H3O6), but our knowledge of them is not satisfactory. The crystallized alkaloid melts at 189° to 190°C., and yields acetic acid at slightly higher temperature.
Pseudaconitine, C36H49NO12, from Aconitum ferox, is highly poisonous. Atisine, C22H31NO2 (from Aconitum heterophyllum), does not present any close analogy to the alkaloids of the other and well-known species of aconite (A. napellus, A. ferox, and A. japonicum). In small doses it is said to be non-toxic, but its action, according to some reports, resembles that of aconite.
Commercial aconitine contains some of the allied principles, which are separated from the alkaloid with difficulty. Ash, not exceeding 6 per cent.
Preparation of Aconitine.—After extracting oil and resin by a suitable solvent, an alcoholic extract is made which is treated with hot water. The aqueous solution is precipitated by adding NH4OH in excess. This precipitate is exhausted with ether-ethereal solution distilled to dryness. Purify residue by dissolving in acidulated (H2SO4) water, again precipitating with NH4OH, etc. This process yields a commercial product which is not free from pseudoaconitine.
ACTION AND USES.—Antipyretic to a certain extent by reducing circulation; depressant of the sensory nerve-ends, the heart, the respiration, and spinal system. lt relaxes the inhibitory apparatus of the heart, and paralyzes the cardiac muscle and its contained ganglia, the respiratory centers, and the spinal cord in all its functions-sensory, reflex, and motor-but does not affect the cerebrum. Murrell has called attention to the fact that the English alkaloid is seventeen times stronger than the German, while the French is variable, but generally between these; the crystalline variety (Duquesnel's or Merck's aconitine) is therefore to be preferred on account of its uniform strength. The dose of the commercial aconitine is 1/64 gr.; the crystallized alkaloid, however, is given in doses of only from 1/300 to 1/250 gr.
Dose of drug: 1 gr. (0.06 Gm.).
- OFFICIAL PREPARATIONS.
- Fluidextractum Aconiti, Dose: ¼ to 2 drops (0.015 to 0.12 mil).
- Extractum Aconiti, Dose: ⅙ to ⅓ gr. (0. 010 to 0.02 Gm.).
- Tinctura Aconiti (10 per cent.), Dose: ½ to 4 drops (0.03 to 0.25 mil).