13. The scale preparations of iron, so called because they are dried
to form scales, are three in number, the base of all being ferric
hydrate:
(a) _Ferrum tartaratum_, dark red scales, soluble in water.
(b) _Ferri et quininae citratis_, greenish yellow scales soluble in
water.
(c) _Ferri et ammonii citratis_, red scales soluble in water, from
which is prepared _Vinum ferri citratis_ (ferri et ammonii citratis 1
gr., orange wine 1 fl. dr.).
Substances containing tannic or gallic acid turn black when compounded
with a ferric salt, so it cannot be used in combination with vegetable
astringents except with the infusion of quassia or calumba. Iron may,
however, be prescribed in combination with digitalis by the addition
of dilute phosphoric acid. Alkalis and their carbonates, lime water,
carbonate of calcium, magnesia and its carbonate give green
precipitates with ferrous and brown with ferric salts.
Unofficial preparations of iron are numberless, and some of them are
very useful. Ferri hydroxidum (U.S.P.), the hydrated oxide of iron,
made by precipitating ferric sulphate with ammonia, is used solely as
an antidote in arsenical poisoning. The Syrupus ferri phosphatis Co.
is well known as "Parrish's" syrup or chemical food, and the Pilulae
ferri phosphatis cum quinina et strychnina, known as Easton's pills,
form a solid equivalent to Easton's syrup.
There are numerous organic preparations of iron. Ferratin is a reddish
brown substance which claims to be identical with the iron substance
found in pig's liver. Carniferrin is another tasteless powder
containing iron in combination with the phosphocarnic acid of muscle
preparations, and contains 35% of iron. Ferratogen is prepared from
ferric nuclein. Triferrin is a paranucleinate of iron, and contains
22% of iron and 2(1/2)% of organically combined phosphorus, prepared
from the casein of cow's milk. Haemoglobin is extracted from the blood
of an ox and may be administered in bolus form. Dieterich's solution
of peptonated iron contains about 2 gr. of iron per oz. Vachetta has
used the albuminate of iron with striking success in grave cases of
anaemia. Succinate of iron has been prepared by Hausmann. Haematogen,
introduced by Hommel, claims to contain the albuminous constituents of
the blood serum and all the blood salts as well as pure haemoglobin.
Sicco, the name given to dry haematogen, is a tasteless powder.
Haemalbumen, introduced by Dahmen, is soluble in warm water.
_Therapeutics._
Iron is a metal which is used both as a food and as a medicine and has
also a definite local action. Externally, it is not absorbed by the
unbroken skin, but when applied to the broken skin, sores, ulcers and
mucous surfaces, the ferric salts are powerful astringents, because
they coagulate the albuminous fluids in the tissues themselves. The
salts of iron quickly cause coagulation of the blood, and the clot
plugs the bleeding vessels. They thus act locally as haemostatics or
styptics, and will often arrest severe haemorrhage from parts which
are accessible, such as the nose. They were formerly used in the
treatment of _post partum_ haemorrhage. The perchloride, sulphate and
pernitrate are strongly astringent; less extensively they are used in
chronic discharges from the vagina, rectum and nose, while injected
into the rectum they destroy worms.
Internally, a large proportion of the various articles of ordinary
diet contains iron. When given medicinally preparations of iron have
an astringent taste, and the teeth and tongue are blackened owing to
the formation of sulphide of iron. It is therefore advisable to take
liquid iron preparations through a glass tube or a quill.
In the stomach all salts of iron, whatever their nature, are converted
into ferric chloride. If iron be given in excess, or if the
hydrochloric acid in the gastric juice be deficient, iron acts
directly as an astringent upon the mucous membrane of the stomach
wall. Iron, therefore, may disorder the digestion even in healthy
subjects. Acid preparations are more likely to do this, and the acid
set free after the formation of the chloride may act as an irritant.
Iron, therefore, must not be given to subjects in whom the gastric
functions are disturbed, and it should always be given after meals.
Preparations which are not acid, or are only slightly acid, such as
reduced iron, dialysed iron, the carbonate and scale preparations, do
not disturb the digestion. If the sulphate is prescribed in the form
of a pill, it may be so coated as only to be soluble in the intestinal
digestive fluid. In the intestine the ferric chloride becomes changed
into an oxide of iron; the sub-chloride is converted into a ferrous
carbonate, which is soluble. Lower down in the bowel these compounds
are converted into ferrous sulphide and tannate, and are eliminated
with the faeces, turning them black. Iron in the intestine causes an
astringent or constipating effect. The astringent salts are therefore
useful occasionally to check diarrhoea and dysentery. Thus most salts
of iron are distinctly constipating, and are best used in combination
with a purgative. The pill of iron and aloes (B.P.) is designed for
this purpose. Iron is certainly absorbed from the intestinal canal. As
the iron in the food supplies all the iron in the body of a healthy
person, there is no doubt that it is absorbed in the organic form.
Whether inorganic salts are directly absorbed has been a matter of
much discussion; it has, however, been directly proved by the
experiments of Kunkel (_Archiv fur die gesamte Physiologie des
Menschen und der Tiere_, lxi.) and Gaule. The amount of iron existing
in the human blood is only 38 gr.; therefore, when an excess of iron
is absorbed, part is excreted immediately by the bowel and kidneys,
and part is stored in the liver and spleen.
Iron being a constituent part of the blood itself, there is a direct
indication for the physician to prescribe it when the amount of
haemoglobin in the blood is lowered or the red corpuscles are
diminished. In certain forms of anaemia the administration of iron
rapidly improves the blood in both respects. The exact method in which
the prescribed iron acts is still a matter of dispute. Ralph Stockman
points out that there are three chief theories as to the action of
iron in anaemia. The first is based on the fact that the iron in the
haemoglobin of the blood must be derived from the food, therefore iron
medicinally administered is absorbed. The second theory is that there
is no absorption of iron given by the mouth, but it acts as a local
stimulant to the mucous membrane, and so improves anaemia by
increasing the digestion of the food. The third theory is that of
Bunge, who says that in chlorotic conditions there is an excess of
sulphuretted hydrogen in the bowel, changing the food iron into
sulphide of iron, which Bunge states cannot be absorbed. He believes
that inorganic iron saves the organic iron of the food by combining
with the sulphur, and improves anaemia by protecting the organic food
iron. Stockman's own experiments are, however, directly opposed to
Bunge's view. Wharfinger states that in chlorosis the specific action
of iron is only obtained by administering those inorganic preparations
which give a reaction with the ordinary reagents; the iron ions in a
state of dissociation act as a catalytic agent, destroying the
hypothetical toxin which is the cause of chlorosis. Practical
experience teaches every clinician that, whatever the mode of action,
iron is most valuable in anaemia, though in many cases, where there is
well-marked toxaemia from absorption of the intestinal products, not
only laxatives in combination with iron but intestinal antiseptics are
necessary. That form of neuralgia which is associated with anaemia
usually yields to iron.