Definition. - The hydrobromide of an alkaloid obtained by the condensation of tropine and mandelic acid.

Atropine may be broken up, by the action of alkalies, into an alkaloid, tropine, and an aromatic acid, tropic acid. Tropine forms ester-like compounds with many acids; the compounds with aromatic acids are called tropeins. Homatropine is one of these tropeins, formed by the union of tropine and mandelic acid; the latter is phenylglycollic acid

Tropic acid (the acid of atropine) is phenylhydracrylic acid.

Scopolamine (hyoscine) is formed by the union of tropic acid with scopoline, a compound similar to tropine.

Properties. - Small, colorless, odorless, rhombic crystals or crystalline powder, having a bitter taste. Soluble in 5.7 parts of water and 32.5 parts of alcohol. It should be kept in well-stoppered vials protected from light.

Dose."Average dose: 0.0005 Gm.'=o.5 milligramme (1/128 grain)." U. S. P. Euphthalmin is a recently introduced mydriatic, having a physiological action.

very similar to homatropine; it is a mandelic acid derivative of beta-eucaine.

Antagonists and Incompatibles. - Muscarine antagonizes the action of belladonna in nearly every particular, and physostigmine, pilocarpus, and aconite counteract many of its effects. Opium antagonizes its action on the cerebrum, pupil, heart, respiration, arterial tension, and kidneys.

Atropine is incompatible with caustic alkalies, tannin, and vegetable infusions containing tannin, an insoluble tannate of the alkaloid being formed.

Synergists. - The mydriatic drugs mentioned aid the action of belladonna.

Physiological Action. - The action of belladonna is dependent upon the amount of atropine it contains.

Externally and Locally. - When locally applied atropine is analgesic, antispasmodic, antisecretory, and mydriatic. When thus used, in combination with absorbable substances - such as alcohol, camphor, animal fats, glycerin, etc. - it diminishes the sensibility of the sensory nerves, and when absorbed from raw surfaces of the skin or from the subcutaneous tissue it is capable of producing systemic effects.

Internally. - Digestive Symptom. - Even small doses produce dryness of the mouth, owing to the greatly diminished secretion of saliva and mucus. The salivary secretion is lessened through paralysis of the peripheral endings of the secretory fibers only of the chorda tympani nerve in the submaxillary gland.

The drug diminishes the secretions from the stomach, liver, pancreas, and intestines possibly in a similar manner. The sweat is diminished through paralysis of the peripheral nerve-endings in the sudoriparous glands. The secretion of milk is reduced by paralysis of the peripheral terminations of the secretory nerves in the mammary glands. The secretion from the bronchial mucous membranes is lessened through the depressing influence of the drug upon the nerve-endings. The secretions of the kidneys are not as profoundly altered as are other glandular products.

Atropine is absorbed readily. It breaks up into tropin and tropic acid and has a marked action on the nervous structures.

Unstriped Muscles. - The peristaltic movements of the intestines are generally decreased by atropine. Very large doses are known at times to cause violent peristalsis and thus are thought to be of value in intussusception.

Circulatory System. - Medicinal doses of atropine or belladonna at first retard the pulse, due, it is thought, to a stimulation of the vagus centers, thus inhibiting the action, but it is quickly accelerated and rendered firmer with increased arterial pressure. The primary transitory action is due to a slight stimulation of the vagi roots, the subsequent quickening of the pulse resulting from paralysis of the peripheral ends of the pneumogastric nerve distributed in the cardiac muscle. The inhibition being thus removed, the heart responds to the influence of the accelerator nerves. The center for these nerves in the medulla is also stimulated by the drug, increasing still further the rapidity of the heart's action. The cardiac muscle itself, being stimulated, renders the contractions of the heart more forcible.

Arterial tension is increased not only by the greater rapidity and force of the heart, but also by the contraction of the arterioles arising from stimulation of the vasomotor center. Very large or poisonous doses lower arterial pressure. This effect is produced by exhaustion of the vasomotor center from over-stimulation, resulting in dilatation of the cutaneous arterioles, which lowers arterial tension and flushes the skin. Overwhelming doses may weaken the cardiac muscle itself from over-stimulation, weakening the heart's contraction, as well as paralyzing the terminal nerve-filaments in the muscles of the vessel-walls, and even the muscular fibers.

Nervous System. - A full medicinal dose of belladonna stimulates the brain, while large doses - and, in susceptible persons, medicinal ones - may produce hallucinations and delirium, accompanied by spectral illusions. The delirium may be mild, joyful, and talkative, or it may assume a violent type. It may, moreover, persist for a long time, after which the patient sinks to sleep, induced either by exhaustion from the delirium or a secondary depressing action of the drug. The motor area is also stimulated.

The spinal cord shares in the stimulation caused by belladonna. The reflexes are at first slightly exaggerated, being afterward diminished. Very often under poisonous doses there is complete motor paralysis, the loss of power occurring first in the lower extremities.

The sensory nerves are depressed, especially when the drug is locally applied, the influence being exerted on their terminal filaments.

Respiratory System. - Medicinal doses quicken and deepen the respirations, owing to stimulation of the respiratory center.

Poisonous doses over-stimulate, and consequently exhaust or paralyze, the respiratory center, the result being slow and shallow breathing and death from asphyxia.

Absorption and Elimination. - Atropine is rapidly absorbed and eliminated, chiefly by the kidneys, but also to some extent by the bowels. It is thought that part of the drug is oxidized by the liver.

Temperature. - Large doses slightly increase bodily heat, probably by increasing the circulation and respiration, consequently augmenting combustion. Ott maintains that belladonna stimulates the heat-center. In cases of severe poisoning from the drug the temperature rapidly falls.

Eye. - Belladonna dilates the pupil, whether locally applied or taken internally. The manner in which atropine dilates the pupil has not yet been satisfactorily explained, the prevailing opinion being that the action is due to a paralysis of the peripheral ends of the oculomotor nerves. The dilatation may be rendered greater by stimulation of the cervical sympathetic, but the fully dilated pupil is irresponsive to light and accommodation.

Atropine increases intraocular tension, rendering it a dangerous drug in glaucomatous conditions.

Untoward Action. - Very frequently there appears, especially in children, an erythematous or scarlatinal eruption, oftener noticeable on the face and neck, but sometimes affecting the entire surface of the body. Redness and pain in the throat may also be present, but no fever, with itching of the skin or desquamation.

Occasionally instillation of atropine into the eye produces profuse lacrimation, edema of the eyelids, and blepharo-conjunctival irritation.

When taken internally in medicinal doses it sometimes occasions in certain persons vertigo, turgescence of the face, hallucinations, erethistic debility, and impaired assimilation.

Homatropine has caused dizziness, uncertainty of gait, fatigue, difficulty in deglutition, and loquacious delirium.

Poisoning. - The poisonous actions of belladonna may be summarized as follows:

The skin is dry and hot; the conjunctivae are congested, with, possibly, edema of the eyelids, and pupils widely dilated; the heart action becomes rapid after ten to fifteen minutes; the face is swollen, while the whole body may be covered with an erythematous rash, and there is a sensation of heat and pain in the throat and difficulty in swallowing. These symptoms usually develop in from fifteen to twenty minutes.

Rapid respirations, muscular weakness, and incoordination of movements appear; the patient becomes dizzy or mildly or violently delirious, continually talking, shouting, or laughing. While there is a constant desire to micturate, there is an inability to pass any urine. At this stage the respirations are slow and shallow. Finally, convulsions may occur, and the patient sink into a comatose condition and die from asphyxia and cardiac exhaustion.

A lethal dose of atropine has been for an adult 0.15 gm. (2.5 grs.) and for a three-year-old child 0.01 gm. (1/6 gr.). The mortality is not high, being stated by Kionka to be about 11.6 per cent. This was the figure of Feddersen in his dissertation study (Berlin) of 103 reported cases from 1880 to 1882. It is of interest to note that a fatal case is reported from the application of a plaster containing 0.18 gm. of atropine to 8 gm. fat (3 gr.). In fatal cases death takes place in from six to eight hours, sometimes as late as eighteen to twenty hours.

Treatment of Poisoning. - Wash out the stomach with solutions of tannic acid, pursuing the treatment with the cautious administration of physostigmine, morphine, or small doses of pilocarpine. Should cardiac failure be pronounced or the patient lapse into a state of stupor, stimulants and the subcutaneous injection of caffeine are indicated, the patient being aroused meanwhile and kept awake, if possible, respiration being maintained by the use of strychnine and by artificial means when necessary. Should the temperature fall below normal, external heat must be applied. It is usually advisable to empty the bladder by means of a catheter.