This section is from the book "Materia Medica: Pharmacology: Therapeutics Prescription Writing For Students and Practitioners", by Walter A. Bastedo. Also available from Amazon: Materia Medica: Pharmacology: Therapeutics: Prescription Writing for Students and Practitioners.
Nux vomica is the dried ripe seed of Strychnos Nux vomica (Fam. Loganiaceae), yielding, when assayed, not less than 2.5 per cent. of alkaloids. It is native in India, Cochin-China, and Australia.
The alkaloids, strychnine and brucine, the two being present in more or less equal quantities. They exist in combination with igasuric acid, an acid which makes a dark greenish color with ferric salts.
All are assayed.
2.5 per cent. of alkaloids. .
1 grain (0.06 gm.).
16 per cent...............
1/6 grain (0.01 gm.).
2.5 per cent ..................................
1 minim (0.06 c.c.).
0.25 per cent.............
10 minims (0.6 c.c).
Ten minims of the tincture of nux vomica must assay to contain not less than 1/50 grain (0.0012 gm.) of alkaloid, equivalent to about 1/80 grain (0.0008 gm.) each of strychnine sulphate and brucine sulphate.
II. Of Strychnine. - The official salts are the nitrate, soluble in 42 parts of water and in 150 of alcohol, and the sulphate, soluble in 32 parts of water and in 81 of alcohol. Dose 1/40 grain (0.0015 gm.). The maximum beginning dose is 1/20 grain (0.003 gm.)- According to their molecular weights, the nitrate contains 84 per cent. of pure strychnine, and the sulphate 77 per cent. In dry air the sulphate tends to become stronger by the loss of its water of crystallization, while the nitrate is permanent.
Much used non-pharmacopoeial preparations of strychnine are: Citrate of iron and strychnine, 1 per cent. Dose, 2 grains (0.13 gm.). Elixir of the phosphates of iron, quinine, and strychnine. Dose, 1 dram (4 c.c.) = 1/65 grain (0.001 gm.) strychnine and 7/13 grain quinine. Syrup of the phosphates of iron, quinine, and strychnine. Dose, 1 dram (4 c.c.) = 1/80 grain (0.0008 gm.) strychnine and 1 3/5 grains quinine. Compound syrup of the hypophosphites. Dose, 2 drams (8 c.c.) = strychnine, 1/70 grain (0.001 gm.), and quinine, 2/15 grain. Compound laxative pills - aloin, 1/5 grain, extract belladonna, 1/8 grain, ipecac, 1/16 grain, strychnine, the pure alkaloid, 1/120 grain (0.0005 gm.). Pharmacologic Action. - On man brucine has the same type of action as strychnine, but it has been estimated to be only 1/30 to 1/8 as strong, hence the strychnine practically represents the nux vomica action.
The taste is intensely bitter - so bitter, indeed, that it is perceptible in a solution of 1 part in 1,000,000 of water. As the result of the bitterness there is a reflex flow of saliva, and the drug has the effect of a bitter upon the taste-buds. (See Bitters.)
After absorption into the blood, the strychnine effect upon the spinal cord results in an increase in the tone of the muscles of the stomach and intestines, and probably in an increase of reflex secretory activity.
Absorption is rapid, especially from the intestines. As reported by one investigator, convulsions came on in thirty minutes after the injection of 1 1/2 grains into the stomach of a cat, while convulsions followed injection of the same amount into the small intestine in ten minutes, and a similar injection into the rectum in seven minutes. Ryan (1912) found absorption of an aqueous solution quite rapid from the stomach. He used the small pouch of the Pawlow stomach, so as to prevent passage of the strychnine into the intestines, while allowing the normal motor activity to go on. Starling states that "strychnine injected under the skin of a limb will exert its poisonous effects on the nervous system long before the drug itself appears in the lymph flowing from the limb."
There is a slight stimulation of the intellect and of the motor areas, in kind like that of caffeine. But in degree it is much less marked, so that strychnine is not a pronounced intellectual stimulant, and has much less effect than caffeine in opposing sleep. The perceptions are all stimulated, pain being more keenly felt, the senses of smell and taste more discriminating, that of hearing more acute, that of touch more sensitive. These are all central effects. The sight is also rendered more keen, particularly in distinguishing colors; and as this effect is produced in only one eye, if the drug is dropped into that eye or if it is injected into the immediate vicinity of that eye, the strychnine is believed to act peripherally on the retinal elements, which it reaches through the lymph-spaces. The optic centers are also probably stimulated. Through these two factors, large doses of strychnine injected into the temple, in partial optic nerve atrophy, will sometimes bring about an improvement in the sight.
If a poisonous dose of strychnine is administered to an animal, a very slight stimulus, such as the prick of a pin, a touch, or the jarring of the table upon which the animal lies, will send it into convulsions. Something has happened to make a tremendous muscular response to an ordinary stimulus. What does the strychnine do? Note the following experiments:
1. Expose the sciatic nerve of a frog and ligate the rest of the limb so as to leave the nerve outside of the ligature. This leaves the nervous connections between the spinal cord and the lower part of the limb intact, but cuts off the limb's circulatory connection with the rest of the body. Inject strychnine into the leg below the ligature, where it can act locally on nerve-endings and nerve-trunk. The reflexes are still intact, because the nerve is left outside of the ligature, but the strychnine does not get to the spinal cord because the circulation is cut off. The prick of a pin below the ligature now meets with just the usual response; therefore the strychnine does not stimulate the nerve-ending or nerves, either sensory or motor. If, now, strychnine is injected above the ligature, the prick of a pin below the ligature results in convulsions.
Dip a frog in 5 per cent. cocaine solution until its skin is just anesthetized, so as to cut off any-afferent impulses from the surface; then give a large dose of strychnine, and no convulsions result. Now generate afferent impulses by stimulating the nerve-trunks, and convulsions follow.