This section is from the "A Practical Treatise On Materia Medica And Therapeutics" book, by Roberts Bartholow. Also available from Amazon: A Practical Treatise On Materia Medica And Therapeutics
The leaves of Digitalis purpurea Linné (Nat. Ord. Scrophulariaceae), from plants of the second year's growth. (IT. S. P.) Feuilles de digitale, Fr.; Fingerhutblätter, Ger.
The boiling water is poured over the digitalis in a suitable vessel and allowed to macerate until cold; it is then strained and the alcohol and cinnamon-water are added, and enough cold water is passed over the residue on the strainer to measure 1,000 c. c. Dose, 3 ij— oz ss.
Fluid extract of digitalis. Dose,
Extract of digitalis. Dose, gr. ss—gr. ij.
Tincture of digitalis. Dose, τηv—3 j.
Digitalis contains an active principle, digitaline. This exists in the amorphous and crystalline form. The amorphous form—the digitaline of Homolle and Quévenne—possesses considerable activity, and, according to some authorities, is quite equal to the crystalline in strength. The crystalline digitaline (Nativelle's digitaline) occurs in needle-shaped crystals and has an extremely bitter taste.
According to Schmiedeberg, digitalis contains digitonine, which strongly resembles saponine; digitaline, which is insoluble in water, and is the chief constituent of Homolle and Quévenne's digitaline; digitalein, which is readily soluble and has the same action as German digitaline; digitoxine, the most powerful, and is the principal constituent in Nativelle's digitaline. Koppe has examined the action of digitaline, digitalein, and digitoxine, and finds that they agree in their action, and with the crude drug, but differ in degree of activity.
Digitaline. A white, or yellowish-white powder, without odor, and having a very bitter taste. Dose, 1/60—1/30 of a grain.
The cinchona preparations, acetate of lead, the sulphate and tincture of the chloride of iron, are chemically incompatible. Tannic acid and the preparations containing it diminish the physiological activity of digitalis. Opium, aconite, lobelia, and the cardiac paralyzers, antagonize some of the actions of digitalis, but the antagonism does not extend throughout the whole range of their influence. The most complete physiological antagonism exists between digitalis and saponine (Köhler), the active principle of Saponaria officinalis, closely allied to senegine. Aconite antagonizes the cardiac action of digitalis, and morphine, also, to a less degree.
Digitalis has a disagreeable, bitter taste. In considerable doses, of the infusion, for example, it disturbs the stomach and gives rise to nausea and vomiting, and frequently purges. Loss of appetite results from its medicinal administration in some subjects, even when the quantity is small; but, in others, the appetite is increased. The active constituents of digitalis diffuse into the blood, but nothing is definitely known as to the action of this agent on the composition of the blood, or the influence which it has, if any, on the morphological elements.
On the heart digitalis exerts a peculiar action which requires attentive examination: it prolongs the diastole and increases the vigor of the systole. A lethal dose arrests the heart in systole, inducing a tetanic state of the heart-muscle. While digitalis increases the power of the systole, the diastole is prolonged, hence the number of pulsations per minute is reduced. With ordinary medicinal doses this slowing of the heart may be considerable, and the pulsations may descend to fifty or even forty per minute. Microscopic examination of the mesentery (Ackermann) and of the web of the frog has definitely ascertained that a marked contraction of the arterioles takes place under the influence of digitalis. The increased power of the systolic contraction of the heart and the greatly-increased resistance in front from a narrowing of the caliber of the vessels produce, as might a priori be expected, a considerable rise of the blood-pressure. When the pulse is greatly reduced by the administration of large medicinal doses, a change from the recumbent to the upright posture causes a remarkable increase in the number, and diminution in the force, of the cardiac pulsations. When lethal doses, short of a sudden toxic effect, have been experimentally administered, the slowing of the heart and rise of arterial tension first produced are succeeded by a quick, feeble pulse, and fall in the blood-pressure. These results are obviously due to the loss of power (paresis) which results from over-stimulation.
A temporary rise of temperature follows the administration of a lethal dose of digitalis, but this rise is soon succeeded by a marked and sustained reduction. Owing to the increased resistance from diminution of the caliber of the arterioles, the actual energy expended by the heart is in part converted into heat. Subsequently the slowing of the circulation, especially through the lungs (Traube), hinders the combustion process, and hence the fall of temperature.
Digitalis in full medicinal doses produces headache, a band-like feeling around the forehead, dizziness, disturbances of vision (mistiness, vibratory movements of external objects, chromatic dispersion, etc.), drowsiness, languor, and a sense of weariness, and it may even cause hallucinations, illusion, and delirium. Digitalis lessens the reflex function of the cord, lowers the sensibility of the nerves, motor and sensory, and impairs the electro-contractility of muscles; but these effects are not produced by medicinal doses, but are toxic in character.
As might be anticipated from a study of its physiological actions, digitalis acts like ergot on the enlarged uterus; it stimulates to energetic contraction the muscular fibers, and in this way arrests uterine haemorrhage. On the genital organs of man it has a similar action; by diminishing the blood-supply to the erectile tissue it lessens the power of erections, and, secondarily, affects the venereal appetite, producing anaphrodisia.
Considerable difference of opinion exists as to the influence of digitalis on the function of nutrition—the metamorphosis of tissue. By some an increase in the production of urea, by others a diminution, has been noted. The truth, most probably, is that it has no real influence on urea formation, and that the variations observed are accidental. The phosphoric acid and chlorides are diminished. In health digitalis affects but little the water of the urinary secretion; according to some the water is diminished, according to others increased. It is difficult to reconcile these opposing statements, in view of the fact which has recently been ascertained by Brunton, that the diuretic action of digitalis in dropsy is not due to the increased blood-pressure, but to a special action on the Malpighian tufts.