The lethal dose of the pure alkaloid being even approximately settled, it is possible to get a more exact idea as to the suitable medicinal dose of the tincture and extract, and also to study more profitably the “quantitative toxicity.” The English officinal tincture, although variable in strength, may for our purposes be regarded as averaging 1 per cent. of alkaloid—that is, in every 100 parts by volume there will be 1 part of the alkaloid by weight, and Fleming’s tincture may be considered as one-third stronger, containing in every 100 parts 1·3 part of alkaloid. The medicinal dose of the P.B. tincture is laid down as from 5 to 15 min.—equal to from ·005 to ·015 grain of aconitine. The German pharmacopœia gives the maximum single dose as 1 c.c. (say 15 mins.), and the maximum quantity to be taken in the twenty-four hours as four times that quantity. As before stated, 2 mgrms. (·030 grain) of aconitine being considered a fatal dose, this is equivalent to about 2 c.c. (30 mins.) of the P.B. tincture, or to 1·2 c.c. (20 mins.) of Fleming’s tincture in a single dose; and on these theoretical grounds I should consider this dose dangerous, and in the absence of prompt treatment likely to be fatal to an adult man. The usual least fatal dose laid down in medical toxicological works, however, is greater than this—viz., 3·75 c.c. (a drachm).
In 1863 a woman took 70 minims of Fleming’s tincture, and a grain of acetate of morphine, and died in about four hours; but as this was a complex case of poisoning, it is not of much value. Fifteen minims of the tincture caused very serious symptoms in the case of a woman under the care of Dr. Topham,[473] the effects lasting many hours. Probably the smallest quantity of the tincture recorded as having destroyed life is in the case of Dr. Male, of Birmingham.[474] He died from the effects of 80 drops taken in ten doses, extending over a period of four days—the largest dose at any one time being 10 drops, the total quantity would perhaps equal ·08 grain of aconitine.
[473] Lancet, July 19, 1851, p. 56.
[474] Med. Gaz., vol. xxxvi. p. 861, quoted by Taylor, Prin. of Med. Juris., vol. i. p. 426.
The P.B. extract is not a very satisfactory preparation, varying much in strength. It may be taken to average about ·6 per cent., and if so, applying the same reasoning as before, from ·26 to ·32 grm. (4 to 5 grains) would be a fatal dose.[475] On the other hand, there is an alcoholic extract which is very powerful, and averages 5 per cent. of aconitine: 40 mgrms. (·6 grain) of this extract would be likely to be fatal. With regard to the root itself, 3·8 grms. (60 grains) have been known to produce death, and from the average alkaloidal contents it is probable that ·648 grm. (10 grains) would be a highly dangerous dose. Dunstan’s researches will now alter probably the whole of the pharmacy of aconite, and the tendency will be to make the preparations of greater activity, and, consequently, to make the dangerous doses smaller than formerly.
[475] But there is a case reported by Dr. Vachell, of Cardiff, in which 2 grains of extract of aconite taken in pills proved fatal. Now 2 grains is the medicinal dose, laid down as a maximum in the pharmacopœia; a complete revolution is, therefore, necessary in the use of these active remedies. No extract or tincture should be used until its approximate strength in active principles is determined.