Syn. Lettuce-opium.

Origin

The name of lactucarium has been given to the concrete milky juice of Lactuca sativa, or common garden lettuce, and of other species of Lactuca, especially L. virosa and L. altissima, which are natives of Europe. it is procured from the stem; as, before this rises, the leaves, which constitute all of the plant now above the ground, contain little or none of the milky juice; though, as brought upon the table, they often have a narcotic smell, and induce drowsiness when freely eaten. it should be collected about the time when the flowers begin to blow; for, if procured later in the season, though the juice may be thicker, it contains, according to Mr. Duncan, of Edinburgh, less of the bitter matter on which its virtues probably depend. The mode of gathering it is to cut off the stem, or incise it longitudinally, and then either absorb the juice which exudes with a piece of sponge or a little cotton, and press it out into a vessel, or scrape it off with the finger or a knife. The juice concretes spontaneously into a solid substance, which is the lactucarium. Our shops are supplied with it from abroad.

Properties

As found in our shops, it is in small, irregular, light, and friable lumps, of a reddish-brown colour, a narcotic odour strongly recalling that of opium, and a bitter taste. it was this resemblance of its sensible properties to those of the medicine referred to, that gave origin to the name of lettuce-opium by which it has been occasionally designated.

Lactucarium is said also sometimes to be in the form of roundish compact masses, weighing several ounces; and, according to Dr. Christison, this is the condition in which it is collected from the garden lettuce; while the variety above described is obtained from the Lactuca virosa, or wild-lettuce. Another form, in which it is prepared on the Continent of Europe from L. altissima, is that of round flat cakes.

Active Principles

From the strong resemblance of the sensible properties of lactucarium to those of opium, it was at one time conjectured that morphia would be found among the ingredients; but this, upon investigation, has not proved to be the case. The odorous principle distils over with water; but, though it is probably a volatile oil, and may have narcotic properties, it has not been sufficiently investigated to justify any positive opinion on the subject. A bitter, crystallizable, neuter principle named lactucin is said to have been obtained from lactucarium; but its claims to be considered as the active constituent of the medicine have not yet been satisfactorily determined; and no practical advantage has hitherto accrued from its discovery. Lactucarium yields its virtues to water and alcohol.

Effects on the System

These have not been investigated with so much accuracy as to enable a well-grounded opinion to be formed in relation to the precise action of the medicine. That it has a composing and soporific effect cannot be reasonably doubted; but the point is yet undetermined, whether it is essentially stimulant or sedative; and we are equally in the dark as to its accessory properties. While Dr. J. R. Cox inferred, from his experiments, that it had the same stimulant properties as opium, Dr. François, who used an analogous preparation of lettuce, under the name of thridace in France, found it to diminish the frequency and force of the pulse, and the temperature of the body. if, as stated by Fisher, it should be found to have the property of directly diminishing sensibility, without ever exciting the circulation (Lond. Med. Gaz., XXV. 863); and if Buchner be correct in comparing the influence of lactucin over the pulse to that of digitalin, and in ascribing to it the properties of lowering the animal heat, dilating the pupil, and producing sleep and stupor; then we shall certainly be justified in placing lactucarium among the cerebral sedatives. So far as can be inferred from other published accounts, the general tendency of experience is in the same direction.

Therapeutic Application

The soporific property of the common lettuce was well known to the ancients, who believed it also to possess antaphrodisiac properties; and Dioscorides speaks of the juice obtained from the wild-lettuce at maturity, as having in a considerable degree the qualities of opium. But to Dr. J. R. Cox, of Philadelphia, belongs the credit of having first drawn attention to the inspissated juice of the common lettuce as a medicine. He made experiments with it towards the close of the last century, which were published in the fourth volume of the American Philosophical Transactions, and from which he inferred that it was identical with the opium procured from the poppy. (Am. Dispensatory, a.d. 1806, p. 408.) The elder Dr. Duncan, of Edinburgh, soon afterwards made similar investigations, and, in his treatise on pulmonary consumption, recommended lactucarium as a substitute for opium, the anodyne properties of which it possessed, without being followed by similar disagreeable consequences. Dr. François called attention to the same subject in France; and the consequence was the introduction of the medicine into use, and its adoption as a standard remedy in the officinal codes of Great Britain and the United States.

Though extremely uncertain in its action, from its variable strength, lactucarium may be employed for calming nervous disquietude, relieving pain, and producing sleep, in cases in which, in consequence of the existence of some contraindication, opium cannot be used. Thus, having little or no stimulant influence over the circulation, it may be used in inflammatory and febrile conditions in which the excitant action of opium might prove injurious. Not having, at least in an equal degree, the property of checking the secretions, it is better adapted to the early stages of catarrhal disease; and, perhaps, its most advantageous application is to the alleviation of cough. it is said, moreover, to be less apt than opium to cause headache, nausea or other disorder of digestion, and constipation; and may agree well with constitutions, which from idiosyncrasy may not be kindly affected by that narcotic.

It has been specially recommended to allay cough in phthisis, catarrh, and other pulmonary complaints; to compose nervous irritation and produce sleep in febrile diseases of all kinds, idiopathic, exanthematous, and symptomatic; to quiet palpitation of the heart; and to relieve pain in chronic rheumatism, colic, gastralgia, and excessive sensibility of the eyes. The dose of it is from five to fifteen or twenty grains; that of the alcoholic extract, from two to five grains. The Edinburgh College formerly directed a Tincture (Tinctura Lactucarii, Ed.), the dose of which was from thirty minims to two fluidrachms.

The Syrup of Lactucarium (Syrupus Lactucarii, U. S.) is at present the only officinal preparation. it is prepared from the lactucarium by first forming a tincture with diluted alcohol, then concentrating this by a careful evaporation, and finally mixing it with syrup. The dose is two or three fluidrachms. A syrup, prepared in France, according to a process originated by Aubergier, is occasionally imported. The dose of Aubergier's syrup, for the ordinary purposes for which the remedy is used, is a teaspoonful.