The concrete milk-juice of Lactuca virosa, Linné"—(U. S. P.).
COMMON NAME: Lettuce-opium.
Description.—(For source, history, and collection of Lactucarium [in part], see Lactuca.) Lactucarium comes to us chiefly from Germany and Scotland, and is also produced in France, although little of the latter product reaches American markets. The Scotch, or English, variety is said to be of better quality than the German. It occurs in angular pieces of various sizes, is brown in color, and earthy in appearance. The German product occurs in brown quarter-sections of plano-convex, circular, or saucer-shaped cakes. French lactucarium comes in small, circular cakes, otherwise resembling the German drug.
The official product is thus described: "In sections of plano-convex, circular cakes, or in irregular, angular pieces, externally grayish-brown, or dull reddish-brown, internally whitish or yellowish, of a waxy luster; odor heavy, somewhat narcotic; taste bitter. It is partly soluble in alcohol and in ether. When triturated with water, it yields a turbid mixture, and, when boiled with water, it softens and yields a brownish-colored liquid which, after cooling, is not colored blue by iodine T.S."—(U. S. P.). Lactucarium does not absorb moisture from the atmosphere; is softened by heat, and at a high temperature burns with a large, white flame. Cold water takes up about a sixth of it, forming a deep-brown infusion; boiling water, proof-spirit, alcohol, and ether a much larger proportion. The addition of acetic acid to water or alcohol improves their solvent powers upon this article. It pulverizes with difficulty. It does not readily emulsionize with water, unless gum Arabic be present. By previous trituration with a small quantity of nitrous ether, it may be readily incorporated with water (Vogeler).
Chemical Composition.—Lactucarium contains neither morphine nor hyoscyamine, nor any other alkaloid (see Lactuca), but is found to consist of the bitter substances lactucin, lactuco-picrin, and lactucic acid, large amounts of caoutchouc and lactucerin (lactucon), a camphoraceous volatile oil (Thieme), sugar, gum, pectic acid, albumen, oxalic acid, mannit, potassium nitrate, etc.
Lactucin (C11H14O4, Kromayer, 1861), one of the bitter principles of lactucarium, may be obtained by extracting lactucarium, with cold alcohol of specific gravity 0.85. It is a colorless, odorless, fusible, neutral substance, crystallizing in rhombic plates, or in pearly-white scales. It dissolves in from 60 to 80 parts of water, is slightly soluble in ether, readily so in alcohol, and in acids. It reduces Fehling's solution, but yields no sugar upon hydrolysis. Lactucic acid (Ludwig, Archiv der Pharm., 1847) is light yellow, very bitter, soluble in water and alcohol, and does not readily crystallize. Alkalies turn its aqueous solution red. By some this acid is considered a prominent active constituent. The mother liquor of lactucin yielded (Kromayer, 1861) lactuco-picrin (C44H32O21). It is a brown, amorphous, bitter body, faintly acid in reaction, soluble in water and alcohol. It is probably an oxidation product of lactucin. Kromayer regards lactucic acid as the product of the oxidation of lactuco-picrin.
By far the most abundant substance in lactucarium is lactucerin (lactucon of Lenoir, 1846) (C19H30O, Flückiger and O. Schmidt, 1876), constituting half or more of its weight. It is obtained by extracting lactucarium with cold, then with boiling alcohol, which leaves caoutchouc undissolved; or by extracting lactucarium with a mixture of 1 part of chloroform and 3 parts of alcohol. It forms odorless, tasteless, colorless needles, soluble in alcohol, ether, benzin, benzol, chloroform, and volatile and fixed oils, but not soluble in water. Its exact chemical nature remains yet to be established (see O. Hesse and G. Kassner, Jahresb. der Pharm., 1886, p. 37; and 1887, p. 65; also Lieb. Annal., 1886 and 1888). Flückiger (Pharmacographia) calls attention to the fact that it is remarkably analogous to euphorbon (from euphorbium), cynanchol (C15H24O) (from Cynanchum acutum, Linné), echicerin (from Alstonia), and taraxacerin (from Taraxacum). Lactucarium is liable to be adulterated with bread crumbs, hence the pharmacopoeial test for starch above given.
THRIDACE is the inspissated, expressed juice obtained, in France, from Lactucarium gallicum s. parisiense, by collecting the stalks near the flowering period, depriving them of their leaves, and then subjecting them to pressure. It is not identical with lactucarium, as was at one time supposed.
Action, Medical Uses, and Dosage.—Lactucarium has never been thoroughly and satisfactorily investigated in relation to its therapeutical influences: indeed, various experimenters differ in their views on this point, some asserting it to be a stimulant and others a sedative. It is, when employed at all, usually given as a calmative and hypnotic, and as a substitute for opium, to which it is to be preferred in many instances, on account of its freedom, from unpleasant after-effects, as constipation, excitement of the brain, etc. However, it is not considered equal in power to opium. The most energetic lactucarium. is said to be obtained from L. virosa and L. altissima. Moderate doses of it act as a narcotic poison on the lower animals, and 10 or 20 grains swallowed by a dog will cause sleep, or the watery solution injected into a vein occasions sleep, coma, and death. It appears to be of use in insomnia, due to mental overwork. A syrup of lactucarium is of value in the cough of phthisis, and even garden lettuce appears to exert a good influence in this disease, tending to allay the broncho-pulmonary irritation. Dose of lactucarium in pill or powder, which is the most efficient mode of administration, from 5 to 20 grains; of the tincture, 30 to 60 drops; of the alcoholic extract, 1 to 5 grains.
King's American Dispensatory, 1898, was written by Harvey Wickes Felter, M.D., and John Uri Lloyd, Phr. M., Ph. D.