This section is from the book "Materia Medica And Therapeutics: An Introduction to the National Treatment of Disease", by John Mitchell Bruce. Also available from Amazon: The pharmacology and therapeutics of the materia medica.
The endings of the third nerve are paralysed in the sphincter of the pupil and in the ciliary muscle, giving rise to the dilatation of the pupil and the disturbance of accommodation. The effect on the pupil is purely local in its cause; the muscle itself is also unaffected; possibly the sympathetic is somewhat stimulated. The amount of confusion of vision produced by the paralysis of accommodation will depend on the normal refraction of the patient's eye, long-sighted persons suffering most. The intra-ocular pressure is not diminished, as is often stated; it is increased by large doses.
The terminations of the chorda tympani in the submaxillary gland are paralysed by atropia, the result being arrest of saliva, and the dryness of the mouth and throat already mentioned. The sympathetic remains unaffected, so that the vessels in the gland dilate as usual under stimulation, and the "sympathetic secretion" can be obtained as before. Probably the mucous glands of the mouth are paralysed by atropia at the same time.
The ends of the sudoriparous nerves in the sweat glands are depressed by atropia, which is the most powerful of all anhidrotics. Therewith the skin is flushed, as we saw-overspread sometimes by a scarlatinoid redness or rash; and the temperature rises at first, but afterwards falls.
The lacteal nerve terminations are paralysed, and the secretion of milk (if present) arrested.
The ends of the vagus (inhibitory apparatus) in the heart may be briefly stimulated by atropia, thus increasing its slowing action on the cardiac centre in the medulla, already seen; but they are quickly paralysed, the pulse rising in frequency to twice its previous rate after full doses; and this frequency cannot be reduced by faradising the vagus. Therewith the force of the systole is not reduced after moderate doses. Very large (poisonous) doses depress the ganglia, and finally even the muscle, and death occurs through cardiac failure, with the ventricle in diastole. The depressor and the accelerator filaments are not affected.
It will be convenient to complete here the account of the action of belladonna on the circulation. The vaso-motor stimulation noted under the medulla, coincides with the cardiac acceleration, and thus the blood pressure is decidedly raised, the heart emptying itself more frequently into tense vessels. Large doses, however, depress the vaso-motor centre; the peripheral vessels relax; the pressure falls; and if this be extreme, it coincides with the paralysis of the cardiac ganglia and muscle, and contributes to the final arrest of the circulation.
The terminations of the vagus in the bronchial walls are paralysed by atropia, the tension of the muscular coat of the bronchi diminished, and the air current thus facilitated. The afferent branches of the vagus in the same parts are also paralysed, thus diminishing sensibility and reflex action, that is, dyspnoea and cough. These effects are in addition to the stimulation of the respiratory centre already noticed.
The inhibitory branches of the splanchnics in the intestinal walls are depressed by atropia, which thus increases the peristaltic movements, and causes relaxation of the bowels. It is doubtful whether the ganglia and plexuses, and the muscular coat, are also affected. The vaso-motor fibres of the splanchnics, however, resist atropia.
Atropia appears to affect the terminations of the nerves of the urethra, bladder, and vesiculoe seminales, but this part of its action is still obscure. Frequent desire and inability to pass water is a symptom of overdoses.
Metabolism and temperature.-Nutritive activity is increased by belladonna, obviously through the increased circulation and respiration; and most of the solid excretions are increased, as will be seen under the urine. The temperature is correspondingly raised; but sinks with the failure of the circulation after large doses.
From its sedative effect on the convolutions, belladonna in full doses has been given in the low delirium of fevers, mania, and alcoholism, especially if opium fail. Neither for this purpose nor as a hypnotic can it he said to he in general use. It has also been recommended in such neuroses as epilepsy, chorea, and megrim; and in some cases relieves the symptoms of these, without effecting a cure.
Belladonna has been given with success in many forms of cord disease, including spasmodic paralysis.
Liquor Atropiae Sulphatis is extensively instilled into the eye as a mydriatic or pupil dilator, for ophthalmoscopic examination, and. to prevent or break down adhesions in iritis; also to paralyse accommodation before determining refraction. The routine employment of atropia in all kinds of eye disease is, however, to be deprecated, as it may sometimes precipitate glaucoma. See Physostigma, page 228.
Bslladonna, and atropia are greatly used as anhidrotics to check the sweats of phthisis, and other hectic conditions. The extract is generally used in pill at bedtime, or the Solution of Sulphate of Atropia when the case can be watched.
Applied in the form of plaster, liniment, or ointment of belladonna, or as a lotion of atropia, this drug is constantly employed as an anti-galactagogue, to " dispel the milk " at any period after delivery. It also arrests mammary abscess.
Belladonna is a valuable remedy in some cases of disease of the heart and vessels, where the indication is to empty the left ventricle quickly, and relax the vessels, without diminishing the cardiac force. Such cases cannot be further particularised here, but it may be said that belladonna is frequently given, either alone or combined with digitalis, thus securing certain advantages of both drugs, whilst otherwise they may antagonise each other. Belladonna is clinically believed to relieve cardiac pain and palpitation, and is always to be preferred to opium for this purpose; probably this effect is chiefly an indirect one, referable to frequent emptying of the ventricles, lowering of the vascular tension, and prevention of distension of the heart. The plaster, or the extract mixed with glycerine, applied to the praecordium, the extract internally, and atropia subcutaneously, are more trustworthy forms for this purpose than the tincture. A combination of morphia and atropia subcutaneously is especially valuable in cardiac distress. See Opium: Combinations of Morphia and Atropia, page 197.