This section is from the book "A Text-Book Of Pharmacology, Therapeutics And Materia Medica", by T. Lauder Brunton. Also available from Amazon: A text-book of pharmacology, therapeutics and materia medica.
Preparation. - Softening the tough seeds by steam, chopping, drying, and grinding them. Exhausting the powdered seeds with rectified spirit which is recovered by distillation. Precipitating colouring matter and acids by acetate of lead. Precipitating strychnine and brucine from concentrated solution by ammonia. Dissolving the precipitate in rectified spirit and crystallising out strychnine from concentrated solution. The brucine being more soluble remains in the mother liquor. The strychnine is purified by washing and boiling with rectified spirit.
Characters. - In right square octahedrons or prisms, colourless, and inodorous.
Reaction. - Pure sulphuric acid forms with it a colourless solution, which on the addition of bichromate of potassium acquires an intensely violet hue, speedily passing through red to yellow. A very active poison.
Impurity. - Brucine from imperfect preparation, and mineral matter.
Tests. - Not coloured by nitric acid (no brucine), leaves no ash when burned with free access of air (no mineral matter).
liquor Strychninae Hydrochloratis. - (Strychnine, 1 part, with 2 of dilute hydrochloric acid, and 24 of spirit to keep it in solution, and water 73)........................................................................................................
Ferri et Strychninae Citras ..........................................................................................
Syrupus Ferri, Quininae et Strychninae Phosphatum (p. 751)....................................
1-2 fl. dr.
U.S.P. Strychnin Sulphas. Sulphate of Strychnine.
Physiological Action. - Strychnine added to water containing low organisms in small doses increases their activity; in large doses it lessens it. The drug lessens oxidation of protoplasm and oxidation taking place in the blood; it also lessens fermentation, but its action on it is not nearly so great as might be expected from its powerful action on higher organisms (pp. 61, 65, 69, 72, 89).
General Action. - The most marked feature in the general action of strychnine is the great increase which it produces in the reflex excitability of the spinal cord and other reflex nerve-centres, such as the vaso-motor and respiratory centres. When the dose is large this increase is so great as to cause convulsions and death.
Taken in small doses strychnine gives rise to a bitter taste and increases the appetite; sometimes also it increases the peristaltic movements of the intestines, and lessens constipation. When taken in small doses for a long time the drug produces increased sensibility of the sensory nerves, so that impressions are felt more acutely and are of longer duration, and the sense of touch is rendered more acute; the field of vision is increased and distant objects are rendered more distinct; the sense of hearing is also sharpened (pp. 226, 229). Taken in larger doses the drug produces increased sensibility more markedly, and excites sexual desire. If pushed still further the drug causes malaise, anxiety, restlessness, twitchings of the muscles, stiffness of the neck and convulsions.
After a dose of half a grain of strychnine symptoms of poisoning appear in a period varying from five minutes to five hours, coming on without vomiting or any other warning, the first symptom being general convulsions; the teeth are clenched, the pupils dilated, and the body forced into the opisthotonic position, resting on the head and feet, with the hands clenched and the arms drawn tightly towards the body; the spasms last from half to one minute, and are followed by a period of relaxation, during which sensibility to reflex stimuli is enormously increased, the slightest stimulus, such as a draught of cold air, bringing on a fresh attack of spasms. Death results either from asphyxia occurring during a spasm, or from paralysis and collapse coming on during a period of relaxation. The diagnosis between convulsions occasioned by strychnine and ordinary tetanus depends (1) on the history of the case, and (2) on the fact that the spasms of tetanus are tonic whilst those of strychnine-poisoning are clonic. In tetanus too the muscles of the jaw are first affected, hence the term 'lock-jaw'; whilst in strychnine convulsions these muscles are not affected before others.
The treatment of strychnine poisoning consists in evacuating the stomach, if possible before the convulsions begin; but, if this cannot be done, chloroform must be given and the stomach washed out whilst the patient is under the influence of the anaesthetic, and, lastly, chloral should be given by subcutaneous injection (10 gr.) or in enema (1 dr. repeated).
Special Action. On the Alimentary Canal. - Strychnine produces, by its bitter taste, an increased flow of saliva; it also increases the peristaltic action of the bowels.
On the Blood. - When mixed with the blood it lessens oxidation to a slight extent, but probably it has little action on oxidation in the living body, from the small doses which can alone be used.
On the Circulation.- It increases the blood-pressure. This is due to several causes : (1) It stimulates the vaso-motor centre directly, or else greatly increases its excitability to the ordinary stimuli it receives, even when the dose is too small to produce convulsions. When these occur, other factors help to increase the pressure. (2) The vaso-motor centre during the convulsions is stimulated indirectly by the action of the carbon dioxide of the venous blood, which accumulates during the asphyxia caused by the convulsions. (3) The violent muscular contractions during the convulsions increase the resistance to the flow of blood through the arteries and capillaries.
After section of the cord in a normal animal, stimulation of a sensory nerve no longer produces vaso-motor spasm; but in an animal poisoned with strychnine it does. The explanation of this is that strychnine increases the excitability of the vasomotor centre to such an extent that that portion of it which is in the cord becomes able to take on to a great extent the normal functions of the whole centre (p. 287).