This section is from the book "Materia Medica Pharmacy, Pharmacology And Therapeutics", by W. Hale White. Also available from Amazon: Materia Medica Pharmacy, Pharmacology And Therapeutics..
Synonym. - Spotted Hemlock. The full grown fruit of Conium Maculatum, Linne (nat. ord. Umbelliferae), gathered while yet green.
Europe and Asia; naturalized in North America.
About 3 mm. long; broadly ovate, laterally compressed; grayish-green; often divided into the two mericarps, each with five crenate ribs, without oil-tubes, and containing a seed which is grooved on the face; odor and taste slight. Resembling conium fruit. - Caraway, anise, dill, all known by having viuae oil-tubes.
The chief constituents are - (1) Coniine, C8H17N, the active principle; a colorless, oily, volatile alkaloid, of a disagreeable odor and acrid taste.
In 100 parts of water. It is easily obtained from the plant by distillation with alkalies. It is readily decomposed by light and heat, and the preparations of Conium are therefore of very varying strengths. Its salts are much more stable. (2) Methyl-coniine, C8H19CN. A colorless, liquid alkaloid. (3) Conhydrine, a nearly inert crystallizable alkaloid.
Incompatibles. - Caustic alkalies, vegetable acids and astringents.
Dose, 2 to 5 gr.; .12 to .30 gm.
Dose, 1/3 to 1 gr.; .02 to .06 gm.
2. Extractum Conii Fluidum. - Fluid Extract of Conium. By maceration and percolation with Diluted Alcohol and Acetic Acid, and evaporation.
Dose, 1 to 5 m.; .12 to .30 c.c
Coniine probably has no influence on the unbroken skin, but it has been thought to be anaesthetic when applied to painful broken surfaces. This is doubtful, for, in the first place, we have no proof that it can be absorbed from sores; and, secondly, experiments show that large doses have to be given to depress the activity of sensory nerves.
Gastro-intestinal tract. - It has no special action here, but it may occasionally give rise to vomiting and diarrhoea.
Circulation. - Coniine is absorbed into the blood, and circulates unchanged. Probably it paralyzes the terminations of the vagus and so increases the rapidity of the cardiac beat. The heart beats long after breathing has ceased.
Respiration. - Owing to the profound paralysis of all motor nerves, and the later depression of the respiratory centre and motor part of the cord, death takes place from enfeeblement of respiration and consequent asphyxia.
Nervous system. - Nerves. - Coniine powerfully depresses all the motor nerves. This depression begins at the periphery, and gradually ascends till the whole nerve, up to the spinal cord, is incapable of responding to stimuli. This leads to paralysis of all the muscles of the body so far as voluntary and reflex motion is concerned, but they themselves are unaffected, retaining their irritability to local stimuli. The sensory nerves are not implicated unless the dose is very large; then their conducting power is slightly impaired. The effects on nerves are well illustrated in the death of Socrates, for he was directed to walk about until his legs felt heavy (motor paralysis), and later, when his foot was pressed he could not feel.
Spinal cord. - This remains uninfluenced till quite late; then, if poisonous doses have been given, the function of its motor cornua is feebly depressed, as is also that of the respiratory centre in the medulla. These actions are probably due to the methyl-coniine. As the amount of this is variable in the different specimens, the exact period at which these effects come on varies with different preparations. In some animals asphyxial convulsions are very marked.
Brain. - Except for the respiratory centre the whole of the brain is unaffected by coniine. Consciousness is preserved until the stage of asphyxia.
Eye. - Coniine, when dropped into the eye, causes immediate contraction of the pupil reflexly from the conjunctival irritation. But soon the pupil dilates, and accommodation is paralyzed; the same usually happens when the drug is given internally. Probably these results are owing to paralysis of the terminal portions of the third nerve, for well-marked ptosis, which is due to this cause, is present.
Coniine is excreted unchanged, chiefly in the urine.