Atropine is used in veterinary practice, from 32·4 to 64·8 mgrms. (1⁄2 to 1 grain) and more being administered subcutaneously to horses; but the extent to which this may be done with safety is not yet established.
§ 449. Action on Animals.—The action of atropine has been studied on certain beetles, on reptiles (such as the salamander, triton, frogs, and others), on guinea-pigs, hedgehogs, rats, rabbits, fowls, pigeons, dogs, and cats. Among the mammalia there is no essential difference in the symptoms, but great variation in the relative sensibility; man seems the most sensitive of all, next to man come the carnivora, while the herbivora, and especially the rodents, offer a considerable resistance. According to Falck the lethal dose for a rabbit is at least ·79 mgrm. per kilo. It is the general opinion that rabbits may eat sufficient of the belladonna plant to render their flesh poisonous, and yet the animals themselves may show no disturbance in health; but this must not be considered adequately established. Speaking very generally, the higher the animal organisation the greater the sensibility to atropine. Frogs are affected in a peculiar manner. According to the researches of Fraser,[496] the animal is first paralysed, and some hours after the administration of the poison lies motionless, the only signs of life being the existence of a slight movement of the heart and muscular irritability. After a period of from forty-eight to seventy-two hours, the fore limbs are seized with tetanic spasms, which develop into a strychnine-like tetanus.
[496] Transact. of Edin. Roy. Soc., vol. xxv. p. 449. Journ. of Anat. and Physiol., May 1869, p. 357.
§ 450. Action on Man.—When atropine is injected subcutaneously, the symptoms, as is usually the case with drugs administered in this manner, may come on immediately, the pupil not unfrequently dilating almost before the injection is finished. This is in no way surprising; but there are instances in which decoctions of datura seeds have been administered by the stomach, and the commencement of symptoms has been as rapid as in poisoning by oxalic or even prussic acid. In a case tried in India in July 1852, the prosecutor declared that, while a person was handing him a lota of water, the prisoner snatched it away on pretence of freeing the water from dirt or straws, and then gave it to him. He then drank only two mouthfuls, and, complaining of the bitter taste, fell down insensible within forty yards of the spot where he had drunk, and did not recover his senses until the third day after. In another case, a man was struck down so suddenly that his feet were scalded by some hot water which he was carrying.—Chevers.
When the seeds, leaves, or fruit of atropine-holding plants are eaten, there is, however, a very appreciable period before the symptoms commence, and, as in the case of opium poisoning, no very definite rule can be laid down, but usually the effects are experienced within half an hour. The first sensation is dryness of the mouth and throat; this continues increasing, and may rise to such a degree that the swallowing of liquids is an impossibility. The difficulty in swallowing does not seem to be entirely dependent on the dry state of the throat, but is also due to a spasmodic contraction of the pharyngeal muscles. Tissore[497] found in one case such constriction that he could only introduce emetics by passing a catheter of small diameter. The mucous membrane is reddened, and the voice hoarse.[498] The inability to swallow, and the changed voice, bear some little resemblance to hydrophobia—a resemblance heightened to the popular mind by an inclination to bite, which seems to have been occasionally observed; the pupils are early dilated, and the dilatation may be marked and extreme; the vision is deranged, letters and figures often appear duplicated; the eyeballs are occasionally remarkably prominent, and generally congested; the skin is dry, even very small quantities of atropine arresting the cutaneous secretion; in this respect atropine and pilocarpine are perfect examples of antagonism. With the dryness of skin, in a large percentage of cases, occurs a scarlet rash over most of the body. This is generally the case after large doses, but Stadler saw the rash produced on a child three months old by ·3 mgrm. of atropine sulphate. It appeared three minutes after the dose, lasted five hours, and was reproduced by a renewed dose.[499] The temperature of the body with large doses is raised; with small, somewhat lowered. The pulse is increased in frequency, and is always above 100—mostly from 115 to 120, or even 150, in the minute. The breathing is at first a little slowed, and then very rapid. Vomiting is not common; the sphincters may be paralysed so that the evacuations are involuntary, and there may be also spasmodic contractions of the urinary bladder. The nervous system is profoundly affected; in one case there were clonic spasms,[500] in another,[501] such muscular rigidity, that the patient could with difficulty be placed on a chair. The lower extremities are often partly paralysed, there is a want of co-ordination, the person reels like a drunken man, or there may be general jactitation. The disturbance of the brain functions is very marked; in about 4 per cent. only of the recorded cases has there been no delirium, or very little—in the majority delirium is present. In adults this generally takes a garrulous, pleasing form, but every variety has been witnessed. Dr. H. Giraud describes the delirium from datura (which it may be necessary to again repeat is atropine delirium) as follows:—“He either vociferates loudly or is garrulous, and talks incoherently; sometimes he is mirthful, and laughs wildly, or is sad and moans, as if in great distress; generally he is observed to be very timid, and, when most troublesome and unruly, can always be cowed by an angry word, frequently putting up his hands in a supplicating posture. When approached he suddenly shrinks back as if apprehensive of being struck, and frequently he moves about as if to avoid spectra. But the most invariable accompaniment of the final stage of delirium, and frequently also that of sopor, is in the incessant picking at real or imaginary objects. At one time the patient seizes hold of parts of his clothes or bedding, pulls at his fingers and toes, takes up dirt and stones from the ground, or as often snatches at imaginary objects in the air, on his body, or anything near him. Very frequently he appears as if amusing himself by drawing out imaginary threads from the ends of his fingers, and occasionally his antics are so varied and ridiculous, that I have seen his near relatives, although apprehensive of danger, unable to restrain their laughter.”[502] This active delirium passes into a somnolent state with muttering, catching at the bedclothes, or at floating spectra, and in fatal cases the patient dies in this stage. As a rule, the sleep is not like opium coma; there is complete insensibility in both, but in the one the sleep is deep, without muttering, in the other, from atropine, it is more like the stupor of a fever. The course in fatal cases is rapid, death generally taking place within six hours. If a person live over seven or eight hours, he usually recovers, however serious the symptoms may appear. On waking, the patient remembers nothing of his illness; mydriasis remains some time, and there may be abnormality of speech and weakness of the limbs, but within four days health is re-established. In cases where the seeds have been swallowed, the symptoms may be much prolonged, and they seem to continue until all the seeds have been voided—perhaps this is due to the imperfect but continuous extraction of atropine by the intestinal juices.
[497] Gaz. hebd., 1856.
[498] A friend of the author’s was given, by a mistake in dispensing, 16 minims of a solution of atropine sulphate, equivalent to 1⁄7 grain of atropine (or 9·3 mgrms). Ten minutes after taking the dose there was dilatation of the pupil, indistinctness of vision, with great dryness of the throat and difficulty in swallowing; he attempted to eat a biscuit, but, after chewing it, he was obliged to spit it out, as it was not possible to swallow; the throat was excessively sore, and there was a desire to pass urine, but only a few drops could be voided. In forty-five minutes he was unable to stand or walk. There was a bright rash on the chest. In two hours he became insensible, and was taken to the Middlesex Hospital, recovering under treatment in about eight hours.