III. Choice of Preparations of Iron

For many of the facts upon which the following conclusions rest, I have pleasure in acknowledging my indebtedness to a memoir by M. Quevenne, published in Bouchardat's Archives for October, 1854, in which are presented the results of a vast number of experiments, made by the author, upon the mode in which iron enters the system. These experiments were performed chiefly on dogs, in the stomachs of which an artificial opening had been made, allowing of the examination of their contents, and of the changes going on in them from time to time.

Almost all the ferruginous compounds, soluble in the gastric liquors, are capable of contributing to the formation of the red corpuscles, and of producing the general effects of iron upon the system. Two striking exceptions are offered in the ferrocyanide and ferridcyanide of potassium (yellow and red ferroprussiate of potassa), both of which are soluble, but neither is capable of exercising the characteristic influence of iron on the system. They are absorbed with great facility into the blood, but they pass out unchanged with the urine; at least the only change produced is the conversion of the red salt into the yellow before elimination.

Solubility in the gastric liquids is essential to the activity of a chalybeate; and the degree of its solubility may be considered as an approximate measure of its absorbability, and therefore of its power. But the solubility or insolubility of the chalybeates in water, is no criterion of their relation to the gastric liquids in this respect On the contrary. some of the preparations most insoluble in water are most readily dissolved in the stomach, as, for example, powdered iron, and the protocar-bonate. Indeed, the soluble salts of iron almost always undergo precipitation in the stomach, before final solution in the gastric liquids. The precipitate is probably formed by reaction with the organic principles either of the food or of the mucus; and, in the absence of acid in the stomach, would remain undissolved. Acids do not ordinarily exist in the stomach while fasting; but, on the introduction of food, and probably of substances excitant to the stomach, though not nutritive, they are secreted with the gastric juice, to the efficiency of which they seem to beessential. The chalybeate, if introduced into the empty stomach, may possibly excite it to the production of these acids; if introduced with the food, must encounter them in the liquid by which this is dissolved. Though precipitated, therefore, it is always subsequently in a greater or less degree dissolved in the liquor of the stomach. Quevenne ascertained that, if the gastric liquid thus holding iron in solution, be treated by au alkali, a portion at least of the chalybeate is thrown down; and this precipitate was always found, on decomposition, to yield nitrogenous products, proving that it contained an organic principle. This was probably albumen. Mitscherlich inferred, from his experiments, that in the stomach albumen unites with the salts of iron to form compounds, of which those containing the protoxide are soluble in water, those containing the peroxide are insoluble; but both are dissolved by the gastric acids. It is probably, then, in this state of combination with albumen. that the chalybeates, taken into the stomach, finally enter the circulation. Of the changes which the absorbed iron undergoes in the blood, in order that it may be fitted to form a part of the red corpuscles, we know nothing; and conjecture is futile.

The above considerations are calculated to aid us in the choice of chalybeates. In reference to their effects on the system, their mere solubility in water is of no advantage. In fact, it is sometimes otherwise; for until they are precipitated, they may act as irritants to the stomach, and thus interfere with absorption, and with their own farther exhibition. Besides, Quevenne has shown that, as a general rule, they yield a less proportion of metallic iron than insoluble preparations to the gastric liquors. Of these latter, however, the sesquioxide of iron, as represented by the preparation officinally denominated subcarbonate, is an exception; as it gives a less proportion of the metal to that liquor than any other chalybeate in use. Upon the whole, then, when the object is to affect the system through the absorption of iron, as soon and with as little inconvenience as possible, it is advisable to select one of the insoluble preparations, as the powder of iron, or, if a soluble one is chosen, to employ the mildest and least irritating, as the tartrate of iron and potasm.. Should a compound insoluble preparation be chosen, one of the proto-compounds should be preferred to those in which the iron is of higher equivalent value; as the protocarbonate, for example, to the sesquioxide. If the object be solely to act on the mucous membrane of the primae viae, as upon the stomach in dyspepsia, or on the bowels in diarrhoea, then recourse should be had preferably to one of the more active of the soluble salts, as the sulphate, or the chloride.

The best period for exhibiting the chalybeate is also a point for consideration. When the aim is to introduce the iron into the circulation, the preparation should be given at the commencement of a meal; as it is then better borne by the stomach, and is placed under circumstances most favourable for solution by the gastric acids. Quevenne ascertained that a dog could bear twice as much, given with food, as upon an empty stomach. A dose which would vomit or purge under the latter circumstances, caused no inconvenience under the former. But, when the operation of the chalybeate is to be confined to the mucous membrane, it should be given on an empty stomach; as it will thus operate with greater promptitude and certainty, while, as the quantity of metal that may enter the circulation is now a matter of indifference, the dose can be regulated according to the effects without inconvenience.

Another fact ascertained by Quevenne is, that the quantity of a chalybeate absorbed is increased somewhat with the increase in the quantity given, but by no means proportionably; so that, in estimating the relative value of two preparations for affecting the system, one yielding iron largely to the blood, the other sparingly, we cannot supply the deficiency of the latter, so as to bring the two upon an equality, by increasing its quantity.

The great multiplication of the chalybeate preparations is unfortunate, as it tends to embarrass the student and young practitioner, without affording him any equivalent advantage; for all the good that can be obtained from the whole catalogue, whether in regard to diversity of effect, or facility of administration, can be equally obtained from onethird, or at most one-half of the number. I have seldom found occasion to prescribe, for internal use. any others than the powder (reduced iron, U. S.), the protocarbonate {pills of carbonate of iron, U. S.), and the subcarbonate, among the insoluble preparations; and the sulphate, the tartrate of iron and potassa, the citrates, the tincture of the chloride, and the solution of the iodide, among those which are soluble. I believe that all the remedial effects which iron is capable of producing can be obtained from these chalybeates, which afford also opportunity for every desirable diversity in the form of exhibition, whether in powder, pill, mixture, or solution in water or alcohol.

The preparations may be arranged under the heads of 1. those in the metallic state, 2. the oxides, 3. the salts consisting of an oxide and acid, and 4. the haloid salts.