Digitals purpurea. Foxglove. N.O. Scrophulariaceae. Tincture from the leaves of the plant. Dilutions of tincture.
DIGITALIS belong to a family of plants that possess similar properties. Other members of the family are strophanthus, scilla, hellebore, convallaria, apocynum and adonis. The active principles of these plants are glucosides, substances containing carbon, hydrogen and oxygen but no nitrogen. Pharmacopoeial preparations are made from the leaves, the tincture of which contains the active principles digitoxin and digitalein. The seeds of digitalis purpurea are not officinal, but are used in the preparations of the digitalins of commerce.
Digitalis in poisonous quantities induces nausea and vomiting with abdominal pain and often diarrhoea. There are general depression, giddiness, headache, discomfort in the cardiac region and muscular weakness. The pulse at first becomes intermittent and then beats regularly at about 40 a minute, finally it becomes rapid and irregular and death occurs in coma.
In poisoning from use of medicinal doses the chief symptoms are headache, giddiness, nausea, vomiting, fainting, and there may be marked slowing of the pulse. Recovery takes place in forty-eight hours if the drug is stopped.
Digitalis has both a local and a general action. When it is locally applied to delicate surfaces like the conjunctiva or to abraded skin it causes painful irritation of the sensory nerves, frequently followed by their paralysis. Digitoxin is the most irritating of the active principles.
The general action of digitalis is shown by its influence on the central nervous system and the heart. On the central nervous system its action is that of a stimulant to the centres in the medulla oblongata, viz., the vomiting and respiratory centres and the nucleus of the vagus; there result vomiting, quickening and deepening of the breathing and slowing of the heart beat.
Circulation.-The most important action of digitalis is on the heart, and its influence is exerted in two ways, through the vagus and by a direct action on the cardiac muscle.
The muscle of the frog`s heart is reduced in conductivity and augmented in contractility and excitability. The effect on conductivity is the first and foremost to be experienced and the result is to slow the pulse. This occurs independently of any influence on the vagus, as it takes place when that nerve is paralysed by atropine.
On the mammalian heart the action is more complicated, as the vagus comes more into play. When only moderate doses are taken the rhythm of the heart is slowed and the diastole of the ventricles prolonged as well as their dilatation increased through the influence of the inhibiting fibres of the vagus on the sino-auricular node, the pace-maker of the heart. At the same time the vigour of each beat is increased by the drug, owing to its augmenting the excitability and contractility of the cardiac muscle by a direct action on it. The slower rhythm is more than compensated by the increase in volume of blood sent out by the more dilated ventricle and by the greater force of its contraction. Consequently the circulation of blood through the arterial system is increased, more blood leaves the ventricle per minute than before, the efficiency of the heart is heightened. When rather larger doses are taken the position is reserved. The vagus slows the heart still more till a point is reached where the increased output at each beat does not make up for the fewer beats, in consequence the total volume of blood sent to the arteries per minute is lessened and the efficiency of the heart is then diminished. With still larger doses the poison has so increased the excitability of the heart muscle that the vagus can no longer hold it in check. Further, the conductivity of the auriculo-ventricular bundle of His is impaired or abolished, so that some only, or perhaps none, of the impulses from the auricle reach the ventricle, the excitable auricles and ventricles beat irregularly and rapidly on their own separate account, there is arrhythmia and a condition of auricular and ventricular fibrillation occurs, which leads to exhaustion of the heart and death. Throughout the whole course of the poisoning both sides of the heart are similarly affected, the two auricles and the two ventricles beat in unison.
Digitalis contracts the blood-vessels by increasing the irritability and contractility of their muscular coats in a manner similar to that of its action on the heart muscle, although the arteries of different areas of the body vary in this respect. The increased arterial tension that would naturally result is compensated by a diminution in the tone of the vasomotor center, so that, on the whole, digitalis does not materially raise the blood-pressure and need not be withheld as a medicine from fear of its doing so.
The glucosides of this drug are very susceptible to destruction in the stomach and upper part of the small intestine and they are very slowly absorbed. Some have been found in the liver, none in the heart, but they have been recovered from the urine and faeces. Digitalis is slow in affecting the heart, but its action on it is prolonged, so much so that the pulse may not return to its normal rate till several days after its administration has been stopped. This makes an accumulation of the drug`s action possible, and medicinal doses, if too long continued, will produce symptoms of poisoning, such as sudden faintings, nausea and vomiting and an alarmingly slow and irregular pulse.
Stomach.-Digitalis causes a certain amount of irritation of the stomach, and at autopsies on fatal cases portions of the stomach have been found inflamed. This will account for the nausea and vomiting produced by the drug, apart from its influence on the heart.
Sexual.-Digitalis produced a good deal of excitement of the male sexual organs, causing continued strong erections and seminal emissions.
The eyes become hypersensitive to light, the lids are reddened, the pupils usually dilated and the vision disturbed by photopsies of various kinds, fiery sparks, flickering, rings of prismatic colours; objects appear green, yellow, or blue, and faces of a corpse-like whiteness. Blind patches (scotomata) are brought out and focusing is difficult.
Head.-The giddiness, fulness and pain in the head and the mental confusion which may go on to delirium that are sometimes observed with digitalis are probably secondary to its disturbance of the circulation.
Urine.-The diuresis seen in the early stages of its action is due to the increased output from the heart, causing more blood to circulate through the kidneys; it is most marked when the drug is given in valvular disease with dropsy.
Liver.-That digitalis has some action on the liver is probable from the jaundice and ash-grey stools that occurred in some of the provers.
Digestive System.-No use is made of the local irritant and anaesthetic actions of digitalis. The stomach and liver complaints for which it is suitable are defined by certain symptoms elicited in the provings; they are thirst for water, burning and scraping in the pharynx, painful feeling of hunger, amounting to ravenous appetite, which is not diminished by food; flatulence, heartburn, eructation of food in mouthfuls, cutting pains in the stomach, tenderness and deathly sinking at the epigastrium; nausea, worse from the smell of food, not relieved by vomiting; jaundice, griping pains and borborygmi in the bowels, and the sudden evacuation of thin, whitish stools. All these symptoms are associated with a slow pulse. It has been useful in stomach complaints from excessive venery and high living and in delirium tremens in high livers.
Sexual.-Digitals is a remedy for spermatorrhoea and for old cases of enlarged prostate with constant desire to pass water.
Heart Diseases.-The principal, and indeed almost the only diseases for which this drug is employed are diseases of the heart. It can be used in material doses to obtain the direct physiological effect of the drug, or in minute doses if its homoeopathic action is desired, but the large and the minute doses are not effective in the same conditions. In doses sufficient to obtain its physiological action it is often very useful in cases where the efficiency of the heart is impaired, whether from valvular diseases or general debility as in anaemia. The inefficiency of the circulation causes imperfect nutrition of the organs, including innutrition of the heart itself, and allows the tissues to become waterlogged and dropsies to form. The direct stimulus given to the heart by digitalis and the resulting improvement in the circulation enable the organs to resume their functions, clear off the superfluous fluid by promoting diuresis, and, above all, by increasing the blood supply to the musculature of the heart itself, to enable it to recover its vigour. As is the case with all stimuli depression follows, but in many cases before this takes place the organs have been reinvigorated and the heart`s nutrition so improved that their functions will be performed, for a time at any rate, rate, quite satisfactorily without continuing the digitalis. If it happens that the medicine cannot be left off without the symptoms returning, there results that the dose will have to be gradually increased to get the desired effect, till finally the heart is exhausted by prolonged stimulation. When the heart is in a state of fibroid change or fatty degeneration from myocarditis digitalis is contra-indicated. The condition in which the drug has been found the most useful is that of auricular fibrillation. In this affection the auricle, for some reason, no longer contracts, as normally, under the control of impulses proceeding from the sino-auricular node, but from a number of points in the wall of the auricle contractions originate, which are irregular and inco-ordinated, with the consequence that no proper contraction of the auricle takes place, and stimuli that are variable in time and force are transmitted through the auriculo-ventricular bundle of His to the ventricle, causing it to contract in a like irregular manner. The pulse is irregularly irregular. Digitalis impairs and finally abolishes the conductivity of the auriculo-ventricular bundle, and so by delaying the impulses in their passage to the ventricle, and by preventing many of them getting through at all, enables the ventricle to beat in a more normal manner. The drug has no influence on the fibrillation of the auricle, that goes on just the same, therefore it is in no sense curative and cannot be discontinued, but it is a most valuable palliative, as it enables the ventricle to go on propelling the blood in a better manner in spite of the disorder in the auricle.
In the very similar condition of auricular flutter digitalis is useful for the same reason that it is efficacious for fibrillation, and fortunately the auricle can in these cases regain its normal action, and then the drug may be considered curative.
Impairment of conductivity in the auriculo-ventricular bundle may be brought about by diseases of those fibres, and may occur as the result of syphilis, rheumatism, diphtheria, influenza and other causes. In this case it is the normal impulse from the auricle that is hindered in its passage to the ventricle. The heart-beat rate is slowed. Some impulses do not get through, a beat is dropped, and the pulse intermits. Intermission may occur after every second, third or any other number of beats. In extreme cases the blockage is total, and then the ventricle provides its own stimulus, but with difficulty, and the pulse-rate is reduced to 40 or less. In bad cases of heart block the condition known as the Adams-Stokes syndrome may occur. The consists of sudden fainting or apoplectiform or epileptiform convulsions. It is caused by an unusually long pause between two pulsations, leaving the brain deprived of sufficient blood. An attack frequently proves fatal.
It is these states of heart block to which digitalis is homoeopathic, and must be given in the usual small doses, not lower than 2x, and in the potencies.
A very slow pulse is not necessarily due to diseases of the auriculo-ventricular bundle of His, thought it may be taken to be so if the heart beat is as low as 40 per minute; it may also be due to over-stimulation of the vagus, probably caused reflexly from the stomach or elsewhere, and will then be suitable for the homoeopathic administration of digitalis.
(1) A very slow pulse.
(2) Pulse intermits every second, third or more beats.
(3) Feeling as if the heart would stop beating if the patient moves (gels., he must move).
(4) Great weakness and sudden sinking of strength.
(5) Jaundice, with nausea and vomiting and white stools.
(6) Faintness, as if dying, felt at the tip of the stomach.
(7) Blueness of the skin, cyanosis.
From movement, especially suddenly assuming the upright position, lying on the left side (palpitation).
From perfect stillness.