Origin. - The dried tuberous root of Exogonium purga (Wend.) Bentham, yielding not less than 8 per cent. of total resin, but not more than 1.5 per cent. of resin soluble in ether. Jalap is a twining herbaceous perennial, growing in damp and shady woods on the eastern slope of the Mexican Andes. It has been introduced into India and Jamaica.

Description and Properties. - Napiform, pyriform, or oblong, varying in size, the large roots incised, more or less wrinkled, dark brown, with lighter-colored spots and short transverse ridges; hard, compact, internally pale-grayish brown, with numerous concentric circles composed of small resin-cells; fracture resinous, not fibrous; odor slight, but peculiar, smoky, and sweetish; taste sweetish and acrid.

Jalap contains two glycosides, jalapin and convolvulin, which are the active principles of the drug.

Dose. - 5-30 grains (0.32-2.0 Gm.) [15 grains (1 Gm.), U. S. P.].

Official Preparations

Pulvis Jalapae Compositus - Pulveris Jalapae Compositi - Compound Jalap Powder (35 percent., with potassium bitartrate). - Dose, 15-60 grains (1.0-4.0 Gm.) [30 grains (2 Gm.), U. S. P.].

Resina Jalapae - Resinae Jalapae - Resin of Jalap. - Description and Properties. - Yellowish-brown or brown masses or fragments, breaking with a resinous, glossy fracture, translucent at the edges, or a yellowish-gray or yellowish-brown powder, having a slight peculiar odor, and a somewhat acrid taste. Permanent in the air. Soluble in alcohol in all proportions.

Dose. - 2-5 grains (0.13-0.3 Gm.) [2 grains (0.125 Gm.), U. S. P.].

Extract of jalap is one of the ingredients of Pilulae Catharticae Compositae and Pilulae Catharticae Vegetabiles.

Physiological Action and Therapeutics. - The purgative action of jalap is developed in the duodenum, where it comes in contact with the bile. The secretion from the intestinal glands is greatly augmented, as well as the vascularity and peristalsis of the intestines. The biliary flow is but little affected.

Purgation is produced by jalap in three or four hours, the evacuations being profuse and watery and attended with griping pain.

Jalap - or, preferably, the compound jalap powder - is a reliable hydragogue cathartic for the removal of dropsical effusions, being especially appropriate for nephritic patients.

Small doses of jalap are serviceable in constipation due to deficient intestinal secretion.

The drug is frequently associated with anthelmintic medicines as a vermifuge.