Quinina

Quinine

Quinine. An alkaloid obtained from the bark of various species of cinchona. A white, flaky, amorphous or crystalline powder, odorless, and having a very bitter taste. It is but slightly soluble in water—in 1,670 parts only. It is given in the form of various salts named below.

Quininae Sulphas

Quinine sulphate. Occurs in white, silky, light, and fine needle-shaped crystals. Soluble in 740 parts of water at 59° F. Dose, gr. j—Эj.

Quininae Bisulphas

Quinine bisulphate. Occurs in colorless, transparent or whitish orthorhombic crystals, or in small needles; odorless, and having a very bitter taste; soluble at 59° F. (15° C.) in ten parts of water and in thirty-two parts of alcohol. The aqueous solution has a strong acid reaction and a blue fluorescence. Dose, gr. v— 3 ss.

Quininae Hydrochloras

Quinine hydrochlorate. Occurs in white, silky, light, and fine needle-shaped crystals; odorless, and having a very bitter taste. It is soluble in thirty-four parts of water at 59° F. (15° C), and in three parts of alcohol. Dose, gr. j—Э j.

Quininae Hydrobromas

Quinine hydrobromate. Similar in physical qualities to the hydrochlorate, but is soluble in fifty-four parts of water at 59° F. (15° C). Dose, gr. j— Э j.

Quinincae Valerianas

Quinine valerianate. Occurs in white or nearly white, pearly, lustrous, triclinic crystals, having a slight odor of valerianic acid and a bitter taste. Soluble at 59° F. (15° C.) in one hundred parts of water and in live parts of alcohol. Dose, gr. j—Э j.

Composition

Cinchona is remarkable for the number and variety of the principles obtained from it, viz., five alkaloids, two simple acids, two tannic acids, and a resinoid substance. The most important alkaloid is quinine, which exists in all varieties of bark, but is most abundant in the yellow or calisaya bark. It occurs in combination with kinic and kino-tannic acids. Quinidine is an alkaloid isomeric with quinine, and may be used as a substitute for the latter in the same dose. It is less bitter than quinine, and its sulphate is more soluble in water. Cinchonine is found in greatest quantity in the pale barks. It unites with acids to form salts, of which the sulphate is most frequently used. Therapeutically considered, cinchonine has about half the strength of quinine. Cinchonidine is an alkaloid isomeric with cinchonine, as quinidine is with quinine. Aricine, which has close analogies with cinchonine, has been found in the Arica or Cuzco bark.

The alkaloids are combined in bark with the acids kinic and hino-vic, chiefly with the former. There are also two kinds of tannic acid, kino-tannic and kinovi-tamiic, and a resinoid substance, kinovin. None of these have thus far been applied to therapeutical purposes, except kinic acid, which has been utilized to form a kinate of quinine, under the belief that a combination of quinine in its natural state would be more efficient as a remedy than as combined with a mineral acid.

When the mother-liquor, left after the crystallization of the alkaloids, is evaporated, a black residue is obtained, which is called chino-idin. This contains amorphous quinine and cinchonine, and probably also quinidine and cinchonidine. It is found in cylindrical sticks, is very bitter to the taste, brittle when cold, but plastic when warm; is but slightly soluble in water. Dose, gr. v— 3 j.

With regard to the quantity of the alkaloids contained in the barks, respectively, it may be stated that the three varieties—pale, yellow, and red—differ only in the relative proportions of their constituents. The pale bark contains most cinchonine, the yellow most quinine, and the red an equal proportion of each.

Administration

The alkaloids of bark are intensely bitter. Quinine being insoluble in the saliva, is less objectionable than its salts. The sweet principle of licorice covers the taste of the cinchona alkaloids. A sufficient dose of quinine may easily be inclosed in a chocolate caramel. The sugar-coated pill, when freshly prepared and by a reputable maker, is a convenient and suitable form for administration; but by keeping it becomes hard and insoluble. The most active form is a solution, the quinine being dissolved by the aid of sufficient dilute acid.

Antagonists and Incompatibles

Substances containing tannic acid in a free state should not be administered with the infusum or decoctum cinchonae. The preparations of iodine (tincture and compound solution) are also incompatible, for they form insoluble compounds with the cinchona alkaloids. The alkalies, alkaline carbonates, and alkaline earths should not be administered with the solutions of the alkaloids, because the latter will be precipitated.

As an agent promoting constructive metamorphosis, cinchona and its alkaloids are therapeutically antagonized by mercury, the iodides, the salts of copper, zinc, and lead.

As Gubler has shown, morphine and quinine are antagonists in respect to their effects on the brain. As regards their action on the sympathetic system, on the heart, and on the temperature, quinine, and belladonna and its alkaloid, are antagonistic.

Synergists

All those agents which promote constructive metamorphosis, as the bitters, the ferruginous preparations, arsenic, and the acids, are synergistic to cinchona.