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.
Strychnia. U. S., Br. - All that has been said of the effects of nux vomica on the system, and of its uses as a medicine, may be considered as applying also to strychnia. When pure it has the advantage over the powder, extract, or tincture, of perfect uniformity of Strength. The only objection to it is the extreme danger from over-doses, which therefore should be avoided with the greatest care.
Strychnia is usually procured from the bean of St. Ignatius, in consequence of its greater richness in this principle than nux vomica. The seeds, properly comminuted, are treated with acidulated water till exhausted; the liquid thus obtained is precipitated by means of lime; the precipitate is treated with alcohol, which dissolves out the alkaloid; the alcohol is distilled off from the tincture; the residue is dissolved with sulphuric acid; the solution having been purified by animal charcoal, is filtered, evaporated, and crystallized; and the resulting sulphate is redis-solved and precipitated by ammonia. As thus obtained, the strychnia contains some brucia; from which it may be freed by repeated crystallization from its alcoholic solution; the brucia being left behind in the mother liquor, in consequence of its greater solubility in cold alcohol. The only disadvantage of brucia is that it renders the preparation weaker in proportion to the quantity present. A little of it does no harm.
Though crystallizable from its alcoholic solution, and sometimes crystalline as sold in the shops, strychnia is more frequently in the form of a white powder, inodorous, excessively bitter, fusible by heat, but not vol-atilizable without decomposition, entirely dissipated when thrown on red-hot iron, almost insoluble in cold water, soluble in 2000 parts of boiling water, freely soluble in officinal alcohol when hot, but much less so when cold, and very sparingly soluble in ether. It may be known, in connection with the above properties, by yielding a violet colour, when a minute proportion of solution of bichromate of potassa is added to a solution of the strychnia in concentrated sulphuric acid. If reddened by nitric acid, it may be assumed to contain brucia. With the acids it forms salts, most of which are soluble in water and crystallizable. The watery solution of salt of strychnia is precipitated by the alkalies and their carbonates, and by tannic acid; but the precipitated matter is medicinally active. Perhaps, however, the most delicate test of strychnia is the physiological test of Dr. Marshall Hall; its powerful effect, namely, in producing tetanic spasms in the frog. One of these animals, put into a liquid containing but an extremely small proportion of strychnia, say one-fiftieth of a grain in the fluidounce, speedily becomes affected with violent tetanic spasms, and perishes. (See Med. and Surg. Reporter, June 24, 1865, p. 85).
To a very considerable degree, strychnia has superseded nux vomica and its other preparations. Being one of the most violent poisons known, it requires to be prescribed and administered with the greatest caution. Many instances of death are upon record, arising from carelessness in the dispensing or use of it.
The commencing dose of strychnia, when quite pure, should not exceed the sixteenth or twelfth of a grain; and, in patients of irritable nervous systems, it would be best to commence with the twenty-fourth of a grain. This dose may be repeated twice or three times a day, and gradually increased, if necessary, in order to obtain its sensible effects. As death has resulted from half a grain, repeated two or three times a day for several days, it would be best never to allow the augmentation of the dose to reach this point. But, as the strychnia of the shops is often impure, larger doses than those mentioned are often necessary for effect. Less than one-sixth of a grain of commercial strychnia will often produce no effect; but, as the strength is generally known only by trial, the dose of any untried parcel should not at first exceed that of the pure alkaloid. A very important caution, in prescribing strychnia, arises out of its variable degree of purity as kept in the shops. When the parcel is changed, unless the one first used is of known purity, the dose should be diminished to a point at which no possible injury could accrue, whatever might be the strength of the new parcel. For children from four to eight years old, the commencing dose should not exceed the thirtieth or fortieth of a grain. The best form of administration is in pill, which may be made with the crumb of bread, or the conserve of roses. Should no effect proceed from ordinary doses, the patient should take a little acidulated drink, as diluted acetic acid, in order to favour its solubility in the stomach; or, should the bitterness not be objectionable, the strychnia may be exhibited in solution, made by slowly dropping into the water in which it is suspended enough acetic, diluted sulphuric, or muriatic acid, to render the liquid clear. For children, the solution may sometimes be advantageously incorporated with syrup, so as to make the dose a teaspoonful.
One of the salts of strychnia, as the muriate, sulphate, acetate, or nitrate, may be substituted for the uncombined alkaloid. The only advantage of the salts is their solubility, so that they may be used in the pilular form, without the necessity, in any case, of following them with an acid. The dose is the same as that of strychnia.
The Sulphate of Strychnia (Strychniae Sulphas, U. S.) is directed, in the U. S. Pharmacopoeia, to be prepared by mixing the alkaloid with distilled water, gently heating the mixture, and gradually adding diluted sulphuric acid until the strychnia is neutralized and dissolved. The liquid, now filtered and evaporated, yields the sulphate in crystals. The salt is in prismatic crystals, colourless and inodorous, but extremely bitter, readily dissolved by water, sparingly by alcohol, and not at all by ether. It melts with heat, and at a high heat is completely dissipated. The dose is the same as that of uncombined strychnia.
Strychnia, or one of its salts, may be used externally by sprinkling it, in the form of powder, upon a surface denuded of the cuticle. The solubility of the salts here gives them an advantage. The quantity first used, if the preparation be pure, should not exceed half a grain of the strychnia, or a quarter of a grain of one of the salts. It may be applied also to the sound skin in the vicinity of the palsied part, in the way of embrocation; the strychnia or one of its salts being incorporated previously with glycerin or oleic acid. One part of strychnia, with a minute quantity of diluted sulphuric acid (a drop or two for each grain), may be rubbed up with fifty parts of glycerin, and a teaspoonful of the mixture rubbed over the paralyzed limb, or along the spine in chorea. (Journ. de Pharm. et de Chim., xxvi. 65, 91, and 303.) Dr. I. Hays, of Philadelphia, has used, with advantage, a solution of acetate of strychnia, dropped into the eye, in order to produce contraction of the pupil, and to excite the muscle of accommodation. (Am. Journ. of Med. Sci., July, 1863, p. 266 ) Strychnia has been used hypodermically in amaurosis and prolapsus ani, and might be similarly employed in other local paralytic affections; the quantity injected at first not exceeding one-half the commencing dose by the mouth.