Origin

Jalap is the root or tuber of Ipomaea Jalapa {Ipomaea Purga, Hayne; Exogonium Purga, Balfour), a climbing plant, with long, slender, twisting stems, cordate-hastate leaves, and beautiful blue or purplish funnel-shaped flowers. This plant is a native of Mexico, growing at an elevation of a mile or more above the sea, in the neighbourhood of the town of Xalapa or Jalapa, from which the medicine derived its name. The root or tuber, after being dug up, is dried whole, or sliced, or deeply incised to aid in the drying, and is then sent in bags to Vera Cruz, whence it is exported.

Properties

The drug as brought to us consists of the dried tubers, either whole, or in longitudinal or transverse slices, and often incised in different directions. They vary, in magnitude, from that of a large chestnut to nearly the size of the fist. They are irregularly pear-shaped, roundish, ovate, or somewhat spindle-shaped, much wrinkled, heavy, compact, hard, and brittle, with a fracture which, in the perfectly sound root, is somewhat shining and resinous in appearance The colour of the outer surface is dark-brown or gray, that of the fractured surface diversified with alternating veins of a dark and shining, and of a yellowish-gray and amylaceous aspect; the former being denser and harder than the latter. The more there is of the darker-coloured portion, the stronger may the root be deemed in purgative power. The powder is yellowish-gray. Jalap has a heavy and sweetish odour; and the powder, when inhaled into the nostrils and throat, is highly irritant, and provokes sneezing and coughing. The taste is sweetish, disagreeable, and decidedly acrid. it yields its purgative properties entirely to alcohol. Water extracts these very imperfectly, if at all, but dissolves certain mucilaginous or extractive matters, which appear to have a qualifying influence over the cathartic action of the jalap, and have been said to be somewhat diuretic. Diluted alcohol is the best solvent.

Chief Constituents. The prominent ingredients of jalap, besides ligneous fibre, are on the one hand resinous matter soluble only in alcohol, and on the other starch, gummy extractive, and saccharine matters which are dissolved by water. The purgative property resides in the former. As the resin is an officinal preparation, the mode of preparing it, and its peculiar properties will be detailed when the different forms in which jalap is administered are considered.

Jalap in tubers is sometimes attacked by worms, which, however, confine themselves to the amylaceous portion, leaving the dark resinous part unconsumed; so that, instead of being weakened, the purgative power of the root is relatively increased. Light, whitish, amylaceous, or woody pieces are inferior, and should be rejected in pulverization. The drug is often adulterated; and, in employing the powder, as obtained indiscriminately in the drug market, I have frequently found it to fail of producing any decided effect, in the ordinary medicinal doses.

Medical Effects and Uses

Jalap was known in Europe near the beginning of the seventeenth century. it is locally irritant; and, when confined in the alimentary canal in dogs, as by tying the oesophagus, two drachms of it are said to have proved fatal, probably by provoking gastric inflammation. in the human subject, in full doses, it operates briskly as a cathartic, producing copious watery discharges, and sometimes causing nausea and griping by its irritant influence on the mucous membrane. it takes rank, therefore, with the hydragogues; but, though somewhat acrid, it is scarcely sufficiently irritant to merit a place among the drastic purges. in excessive doses it may produce hypercatharsis, and thus possibly endanger life in feeble persons; but I have met with no instance of death from it on record. in the ordinary medicinal doses, it is perfectly safe, and may be given even to children without hesitation when indicated. it has no heating effect on the system, and no direct tendency to excite the circulation. it probably operates mainly by a direct influence on the alimentary canal; but it is said to purge when applied to a wound, and would seem, therefore, to be capable of acting through the circulation.

Jalap may be administered in any case, where a cathartic of brisk and rather quick action is required; and may, therefore, be given in febrile and inflammatory diseases, with a sthenic state of system; and its hydragogue property particularly adapts it to dropsical affections, in which the. purgative treatment may be preferred. it is, however, seldom administered alone; being generally employed to increase the action of other cathartics, given with some special view.

It is very often combined with calomel, in the treatment of cases requiring the stimulant influence of the latter remedy upon the liver; as in the commencement of bilious and yellow fevers, hepatic inflammation, and the congestion of the portal circulation, so apt to occur in hot seasons and tropical latitudes. The powerful revulsive influence of this combination upon the abdominal viscera renders it also peculiarly useful in strong vascular determination to the brain, as in existing or threatened apoplexy, meningitis, and acute mania.

Another frequent combination of jalap is with cream of tartar, the refrigerant influence of which unites with the powerful hydragogue action of the former, to render the mixture efficacious in dropsies, particularly those of a febrile or inflammatory character. The same combination is very useful in rheumatic and scrofulous inflammation of the larger joints, attended with some fever. The late Dr. Physick used to employ it with great effect, in connection with rest, and a restricted diet of mush and milk, in the treatment of inflammation of the hip and knee joints in children. He gave a full dose, two or three times a week, and noticed that, instead of becoming emaciated, children not unfrequently grew fat under the treatment, as the local disease diminished.

Administration

The dose of jalap is from fifteen to thirty grains. Twenty grains is a full medium dose, if the medicine is of good quality. To a child three or four years old from four to eight grains may be given. For children younger than this the medicine is rarely required.

A favourite combination of Dr. Rush was ten grains of calomel and ten of jalap. Five grains of the former and fifteen of the latter may often be given advantageously.

When combined with cream of tartar, from ten to twenty grains may be administered with one or two drachms of the salt. in the officinal Compound Powder of Jalap (Pulvis Jalapae Compositus, U. S.) one part of jalap is mixed with two of bitartrate of potassa, and the dose of the mixture is from thirty grains to a drachm. in the British preparation of the same name, five parts of jalap are mixed with nine of acid tartrate of potassa (cream of tartar) and one part of ginger; so that the proportion of jalap to the whole mass is the same as in our own. in both, the proportion of bitartrate of potassa is too small to have any very perceptible effect.

The powder of jalap may be given, mixed with syrup or molasses. its large bulk renders it desirable to obtain the virtues of the medicine in a concentrated state. Hence different extracts have been prepared, and are much used. According to the late Dr. Duncan, the aqueous extract of jalap purges moderately with little griping, and increases the flow of urine. That obtained from the root previously exhausted by alcohol, does not purge, but acts as a diuretic. The alcoholic extract purges actively, and often gripes severely. The inference is that, to obtain the virtues of jalap in an extract, the best measure is to employ both menstrua. This plan has been adopted in the U. S. Pharmacopoeia.

Extract of Jalap (Extractum Jalaps, U. S., Br.) is prepared by first exhausting jalap with alcohol, and subsequently with cold water, evaporating the tincture and infusion separately to the consistence of honey, then mixing them, and evaporating to dryness. A reddish-brown extract is thus procured, having all the medical properties of jalap, and producing the same effects in a dose somewhat more than half that of the powder, say about twelve or fifteen grains. it is, however, much more used in combination than separately, and is one of the ingredients in the compound cathartic pills.

The Resin of Jalap (Resina Jalaps, U. S., Br.; Extractum sive Resina Jalaps, Ed.; Alcoholic Extract of Jalap) is prepared by treating jalap with alcohol, concentrating the tincture, then pouring it into water, and separating the precipitate formed, which is to be thoroughly washed with water and dried. The result of the British process is essentially the same. The U. S. resin, as thus obtained, though sufficiently pure for practical purposes, is somewhat coloured. if it be desired to procure it colourless, the jalap should be mixed with animal charcoal, and then percolated with alcohol; and the tincture thus obtained should be precipitated with water. The resulting product is perfectly white, and operates actively. But the resin of jalap is apt to act harshly, and to produce griping pains; and it is considered best to modify it by admixture with some demulcent substance, as sugar or almond emulsion. it is probable that the mucilaginous and extractive matters in jalap serve a useful purpose, by qualifying the harshness of the resinous ingredient, through their intimate admixture. The U. S. and British extract is, I think, on this account preferable; and if it be the fact, as has been supposed, that the matter soluble only in water acts as a diuretic, this is another ground for the preference of it, especially in dropsical diseases. The dose of the resin of jalap is from two to five grains.

Tincture of Jalap (Tinctura Jalaps, U. S., Br.) is officinal with both the British and American authorities. The dose is one or two fluidrachms, which may be added to cathartic infusions or mixtures, to give them increased activity, or render them somewhat more stimulant to the stomach.