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..
Digitalis is sometimes used externally in the form of a poultice made from the leaves, and placed over the loins in case of renal congestion.
It is one of the most valuable drugs we have. It is chiefly given in cases of cardiac disorder.
Mitral regurgitation. - If in any case of this variety of heart disease the organ is beating feebly, irregularly, and rapidly, digitalis in moderate doses will probably strengthen, regulate, and slow the beat. It will cause the left ventricle to contract more forcibly and to act synchronously in all its parts; hence the mitral flaps will be better approximated, the regurgitation will be less, and more blood will be sent on into the arterial circulation. The prolonged diastole will also be of great advantage, for it will allow more time for the blood to flow from the dilated auricle, and from the right side of the heart and venous system generally, into the left ventricle. In mitral regurgitation, as is well known, venous engorgement and oedema of the lungs, of the right side of the heart, of the liver, the kidneys, and subcutaneous tissues is very common. Digitalis, by improving the venous flow towards the heart, will ameliorate all these symptoms. It might be supposed that by constricting all the peripheral arterioles it would impede the arterial flow, because the heart will have to contract against a greater peripheral resistance, but this disadvantage is never enough seriously to hamper the increased cardiac power; and it must be remembered that it is a great advantage to the circulation to have a proper peripheral arterial resistance, for without that, the elastic coat of the arteries cannot aid the arterial flow. If, as it usually does in these cases, digitalis acts as a diuretic, this will be of great value in removing the oedema, and in causing the scanty high-colored urine to become pale and abundant. The improvement in the circulation relieves the cardiac pain and distress which so commonly accompany mitral regurgitation, the lividity passes off, the dyspnoea decreases, and usually in a day or two a wonderful improvement in the patient's condition takes place. The more any case of mitral regurgitation deviates from the above oedematous type, the less good, as a rule, will digitalis do. Thus cases in which there is much pain and distress, and but little regurgitation, are not so often benefited, although even of such cases many are improved. Sometimes the vomiting caused by digitalis prohibits its use. Fatal syncope may occur in those taking digitalis if they are too suddenly raised from the prone to the upright posture.
Mitral constriction. - In this condition it is obvious that it will be a great advantage to lengthen the diastole, for then there will be a greater chance that the diastole will be long enough to allow the normal amount of blood to pass through the constricted orifice. In proportion as this end is attained, the oedema, lividity, and other signs of backward venous congestion will be relieved, and if the digitalis induces diuresis, this is very valuable in aiding the reduction of the oedema.
Diseases of the tricuspid valve. - In both tricuspid constriction and tricuspid regurgitation, digitalis will be beneficial in the same way as in similar affections of the mitral valve. As a rule, however, it does less good when the disease is on the right side of the heart.
Aortic regurgitation. - Often digitalis is harmful, for by prolonging the diastole more time is allowed for the blood to flow back through the imperfectly closed aortic orifice, and hence there is great danger of fatal syncope. The drug should only be given in cases of aortic regurgitation, when the heart is very rapid, or when there is evidence that not much blood regurgitates, or when there are reasons, such as the coincident presence of aortic obstruction, for wishing to strengthen and regulate the contraction. The dose must be small and the effects must be carefullv watched
Aortic constriction. - This, unfortunately, is usually accompanied by aortic regurgitation; but sometimes when it is wished to increase the force of the beat, and so to drive more blood through the constricted aortic orifice, digitalis is useful, or when, as a result of the obstruction, mitral dilatation and consequent regurgitation, with much pulmonary and venous engorgement, have set in. Many cases of pure aortic obstruction do not require drugs, for the heart hypertrophies sufficiently to overcome the obstruction.
Brighfs disease. - In cases of contracted granular kidney in which the cardiac hypertrophy has been unable to overcome the peripheral resistance, and consequently the left ventricle and with it the auriculo-ventricular orifice has dilated, and mitral regurgitation has therefore ensued, digitalis may be of service for the reasons given elsewhere (see p. 425). A diuretic pill, often used for this condition, consists of calomel, digitalis, and squill a grain of each; .06 gm. made up with extract of hyoscyamus. Otherwise, in chronic Bright's disease, digitalis is not a suitable diuretic, for it raises the tension of the pulse, which is already high. In the earlier stages of acute Bright's disease it has been given as a diuretic, but it is questionable whether it is right to dilate the vessels of an acutely inflamed organ; further, digitalis is always, unless the heart is diseased, an uncertain diuretic, and even in the early stage of acute Bright's disease the arterial tension is somewhat raised. In chronic tubal nephritis, uncomplicated by cardiac disease, it is worse than useless, for it has no effect on the renal cells, and it raises the blood-pressure.
Diseases of the cardiac muscle. - If the heart be fatty, or otherwise degenerated, digitalis rarely does good, for it is harmful for the diseased heart to have to work against the increased arterial tension, and it is said that there is danger of rupture of some of the degenerated fatty fibres. The weakly acting heart that is met with after pericarditis, typhoid fever, scarlet fever, rheumatism, and other acute diseases, even if no valvular defects are present, is markedly strengthened by digitalis. For this purpose it may be combined with caffeine, or two drachms 8. c.c of the infusion may be given, with three minims .20 c.c of stronger ammonia water, in a little water. Each contraction is more efficient, and the prolonged diastole allows more time for the muscle to rest. It is clear that in the course of twenty-four hours this additional repose, although but little in each cycle, will amount to a considerable time. Many men who have practiced rowing or other hard exercise to excess, suffer from shortness of breath, and the apex of the heart is found to be a little outside the normal position, but there is no demonstrable valvular lesion. This condition, which also occurs in soldiers after a long campaign, is much benefited by digitalis. The dilatation of the right side of the heart that so frequently accompanies chronic disease of the lungs may be, but usually is not, improved by digitalis.
Functional diseases of the heart. - The irregular, palpitating beat, often seen apart from any organic disease, may be benefited markedly by digitalis; but it must be remembered that this condition is commonly a result of indigestion, in which case the right treatment is, if possible, to cure the dyspepsia, and if digitalis is given at all, to do so cautiously, for it may excite indigestion. The functional affections of the heart met with in highly neurotic subjects may be, but are not often, benefited by digitalis.
Exophthalmic goitre may improve under a long course of digitalis; but generally this treatment fails.
Haemorrhage. - Although digitalis contracts the arterioles, it is not often given as a haemostatic, for the increased blood-pressure may lead to greater haemorrhage, but it may be useful in the pulmonary haemorrhage due to disease of the mitral valve.
Alcoholism. - Moderate doses of digitalis have been said to be serviceable in chronic alcoholism on account of their stimulating effect on the circulation. Enormous doses have been given empirically in delirium tremens, but generally without any good result.
Uterus. - Because of its power to contract the uterus, digitalis may be useful in menorrhagia.
Digitalis is said to be useless if the patient suffers from high fever.
It is often desirable to combine fluid preparations of digitalis with iron salts, the resulting mixture, which is usually inky from the action of the iron on the tannic acid in the digitalis, can be clarified by the addition of a little diluted phosphoric acid. Because of this difficulty the powdered digitalis leaves are often made into a pill with dried ferr6us sulphate.
Antagonism between Digitalis and Aconite. - Aconite is a cardiac poison, weakening instead of strengthening the beat; it dilates the peripheral vessels, it lowers the blood-pressure, and after death the heart is always found in a condition of diastole. In all these points it is antagonistic to digitalis, but the action of aconite is very rapid, that of digitalis very slow. Therefore these drugs are not practical antidotes to each other in poisoning. Saponin and senegin are considered to be the most complete physiological antidotes.
Digitalis is cumulative. Patients who have taken it for a long while sometimes suddenly show symptoms of poisoning without any increase in the dose. This is because the drug is not excreted by the kidneys so fast as it is absorbed, therefore it accumulates in the body. Digitalis should be stopped so soon as symptoms of gastro-intestinal irritation supervene, or the pulse becomes abnormally slow.