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..
The chief action of cornutine is on voluntary and involuntary muscle, which is stimulated to contract, hence prolonged muscle curves, increased peristalsis of the intestines, tonic contraction of the uterus, and consequent rise of blood-pressure. It also causes convulsions. Sphacelic acid also acts directly on the muscular tissue of arterioles and the uterus, causing it to contract, and in addition it produces an actual thickening of the walls of the arterioles. These substances are rarely given separately, and the following account refers to the action of ergot itself.
Gastro-intestinal tract. - The unstriped muscle of the intestine is stimulated by ergot, and this leads to greatly increased peristaltic movements, sometimes strong enough to cause relaxation of the bowels. The vessels of the intestine are constricted, in part because of the contraction of their own muscular fibres, and in part because of the contraction of those of the intestinal muscular coat. The result is that the intestine is blanched.
Blood. - The active principles of ergot are readily absorbed, but they are not known to produce any effect on the blood.
Heart. - The activity of the heart muscle is depressed by ergot; therefore the rate of the pulse falls, and consequently at first the blood-pressure may fall.
Vessels. - But the fall of blood-pressure is soon followed by a great rise, and this is due to the general contraction of the arteries all over the body; they can, in some parts, be seen to become smaller. The rise of pressure is most marked in the pulmonary artery, and here there is no primary fall. The veins are contracted to a less extent. This vascular contraction is less if the spinal cord is destroyed, from which it is fair to infer that it is partly due to the action of ergot on the vaso-motor centres in the cord, but the drug acts largely directly on the muscular coat of the vessels. Because it contracts the arterioles it is haemostatic If the ergot be taken for a long time the contraction of the arterioles, together with the associated thickening of their walls produced by sphacelic acid, lead to gangrene of various parts of the body, and this was a prominent symptom of the ergotism (chronic poisoning by ergot) which used to be seen in the very poor who could get no better food than rye infected with Claviceps purpurea. Enormous single doses of ergot appear to paralyze the vaso-motor centres, and then the blood-pressure falls from vascular dilatation and cardiac depression.
Nervous system. - Medicinal doses, or even an enormous single dose, very rarely affect the nervous system, but if ergot be taken for a long time a peculiar train of symptoms sets in; they constituted the second variety of chronic ergotism in the times when diseased bread was eaten. The sufferer first complained of itching and tingling, and a sensation of insects running over the skin; this was followed by numbness and local anaesthesia. These symptoms first appeared in the hands and feet, but spread over the whole body. They were followed by tonic contractions of various muscles, especially those of the extremities. The muscular power was lessened, and the gait was staggering. Dimness of vision and loss of hearing, and epileptiform convulsions were sometimes present. This variety of ergotism was usually accompanied by vomiting and diarrhoea. Death occurred from exhaustion.
Uterus. - Ergot powerfully excites the pregnant uterus of women and lower animals to contract and expel its contents. It is therefore called an ecbolic. It is not decided whether this effect is due to the action of the drug on the organ itself or on the spinal centres. Ergot has very little power to cause contraction of the unimpregnated uterus.
The flow of urine, of saliva, of sweat, and of milk is diminished by ergot, probably because of the general vascular constriction.
The chief use of ergot is to cause efficient contraction of the uterus after labor, and so to diminish the risk of post-partum haemorrhage. If there is any likelihood of profuse bleeding it should be given subcutaneously, so that it may act rapidly.
Ergot should not be administered before the child is expelled, for the contraction produced by it not only gradually becomes more severe, but more prolonged, so that ultimately the uterus remains tightly contracted for several minutes; that is, of course, dangerous to the life of the child, and if the resistance be very great, may lead to rupture of the uterus. The modern practice is to forbid its use until after the expulsion of the placenta.
This drug has often been given as a haemostatic in haemoptysis and other haemorrhages from different parts of the body. Some authors claim great success. Frequently it fails, and it may, by the general rise of blood-pressure, do more harm than good. It is difficult to estimate its value, for so many haemorrhages will stop, even if no drugs are given. It has been used to check the night-sweats of phthisis, and as an antigalactagogue.
It is often desirable to combine the fluid extract of ergot with ferric chloride. Because of the tannic acid in the ergot an inky mixture results; but this may be clarified by the addition of a little citric acid, and the taste may be covered with chloroform water.