This section is from the book "Materia Medica And Therapeutics Inorganic Substances", by Charles D. F. Phillips. Also available from Amazon: Materia medica and therapeutics.
Compounds of iron-with the mineral acids act as caustics, irritants, or simple astringents, according to the kind and strength of preparation used; they are also, to some extent, antiseptic. A caustic, destructive action is exerted by the solid per-chloride, especially upon raw surfaces or mucous membranes, but it is not so deep or thorough as that of the mineral acids alone, because of the rapid coagulation of albumen. The astringent effect of dilute preparations is explained partly by such coagulation, and partly by the constriction of capillaries induced.
Kulischer has made curious experiments to test the comparative effects of certain astringents and haemostatics; having divided some blood-vessels in the limbs of frogs, he stayed the bleeding with different astringents applied for various lengths of time, and then injected liquid into the larger blood-vessels, and calculated the amount of force required to reopen those that had been divided and closed; from his results he concluded that of iron solutions a strength of 30 per cent. gave the best results, and the good effect was proportioned rather to such strength than to the duration of its application (Schmidt's Jahrb., Bd. clxix., 1876). Some researches by Rosenstirn upon the same subject, though conducted in a different manner, show also how much the action is dependent upon a definite strength of solution, and enable us to compare the effect of iron with that of other astringents. He examined and measured, under the microscope, the amount of contraction of blood-vessels in a frog's mesentery after application of 10 per cent. solutions of nitrate of siver, acetate of lead, and perchloride of iron, and the last acted not at all; he then used 50 per cent. solutions, and found the iron one very effective - it narrowed both veins and arteries at the place of application, arrested circulation, and acted as a true styptic on the blood itself; the adjacent vessels became dilated.
The coagulum formed in the living vessel by perchloride of iron is soluble, to some extent, in the stream of alkaline blood, and especially so if the astringent solution used be unduly weak; it is also soluble in slightly acid liquids, but is rendered more consistent by combining the iron with alkaline chlorides (Piazza: Bulletin de Therapeutique, 1868). The blood-clot, with lactate of iron, is said to form more slowly, and to be more permanent.
The antiseptic powers of astringent iron preparations are connected with the coagulation of albumen, and strong solutions are fatal to the lower forms of vegetable life. Ferreil ascertained that the neutral strong solution of perchloride arrested decomposition in a blood-clot (when it had commenced), and formed with fresh blood a coagulum that remained unaltered for many months (Union Medicale, 1859, p. 374). Similar observations have been repeated since, but the irritant properties of the strong iron chloride preparations make them less suitable for surgical disinfectant purposes than they would otherwise be, and carbolates, sulphates, etc., have superseded them.
Under the ordinary use of neutral preparations of the drug, the pulse becomes more full and forcible, and the color of face and mucous membranes more florid. It is commonly said that if they be pressed beyond a certain point, symptoms of plethora and of congestion set in, as shown by flushes and giddiness, engorged viscera, and tendency to hemorrhage; but if the patient have good air and exercise, and moderate food, such effects are not likely to occur. The blood will not take up more than a certain amount, and will protect itself by non-absorption, rather than by elimination. Hirtz even asserts that he has never seen congestive symptoms, vertigo, etc., except from the excessive use of chalybeate waters containing carbonic acid, to which he attributed them (Nouveau Diet.).
According to Sasse and Pokrowsky, the use of iron salts increases the heart-action, and Laschkewitsch proved increased blood-pressure in animals taking even small doses (Husemann). In illustration of the effect of large doses (though complicated by alcohol), may be quoted the case of a woman who swallowed 1 oz. of the tincture of perchloride, during an excited condition; the pulse became quick and small, the eyes injected, and the face flushed; convulsive attacks occurred, but were probably hysterical; she recovered after free vomiting (Warburton: Lancet, i., 1869). In disease, on the other hand, there is evidence sometimes of a sedative effect on the circulation. Giacomini records a slow and feeble pulse, pallor, etc., after 20 to 40 gr. of carbonate; and Pize found it lower the pulse and quiet the circulation in purpura and chlorosis, when accompanied with palpitation; in the former case, some gastric irritation was probably caused; in the latter, good effects resulted probably from improved blood-condition. I have known the acetate quiet the circulation when the perchloride did not do so.