Lobelia inflata is an annual or biennial plant common in roadsides and neglected fields throughout the Eastern United States and Canada, usually a foot or more in height, with a fibrous root, and a solitary erect, angular, very hairy stem, much branched about midway, but rising considerably above the summits of the highest branches. The leaves are scattered, or alternate, petiolate, the upper sessile, ovate, or oblong, about two inches (5 cm.) long, irregularly toothed, pubescent, pale green. The flowers are numerous, small, disposed in leafy terminal, axillary racemes. The calyx is five-toothed and much inflated in fruit. The corolla, which is of a delicate blue, has a labiate border, with the upper lip divided into two, the lower into three segments. The united anthers are curved, and enclose the stigma. The fruit is an oval, striated, inflated capsule, crowned with the persistent calyx, and containing, in two cells, numerous very small, oblong, reticulated brown seeds. Most of the commercial supplies of the drug come from Massachusetts, Michigan and New York.

All parts of it are medicinal, but, according to Eberle, the root and inflated capsules are most powerful. The plant should be collected in August or September, when the capsules are numerous, and should be carefully dried. The German Pharmacopoeia directs that Lobelia should be gathered at the end of the flowering period. A number of the foreign Pharmacopeias do not permit the inclusion of the fruit. The drug of commerce oft times is collected late in the season after most of the leaves have fallen and the plant has gone to seed. At times the commercial drug consists of the entire herb, and again may consist chiefly of the thick and inert stems. It may be kept whole or in powder. As found in commerce, it is often in oblong compressed cakes, prepared by the Shakers or the herb dealers. It has been suggested that in cultivating Lobelia inflata the seeds should be planted in the autumn. (Ann. Rep. U. S. Dept. Agric., 1905, p. 147.)

Dried lobelia has a slightly irritating color, and when chewed, though at first without much taste, soon produces a burning acrid impression upon the posterior parts of the tongue and palate, very closely resembling that occasioned by tobacco, and attended in like manner with a flow of saliva and a nauseating effect.

Description and Physical Properties.
Unground Lobelia. � Leaves alternate, sessile or narrowing into a short petiole, usually more or less broken; when entire, blades ovate or oblong from 2 to 9 cm. in length, obtusely toothed or irregularly serrate-denticulate, each, tooth with a yellow-brown, gland-like apex; pale green and with scattered bristly hairs; stem cylindrical, coarsely and irregularly furrowed, yellowish-green, occasionally purplish and with numerous spreading hairs; flowers pale blue, in a long, loose raceme with short pedicels, calyx tubes ovoid, with 5 subulate teeth, corollas tubular, from 3 to 4 mm. in length, 5-parted, the upper 2-lobed portion cleft nearly to the base; stamens with anthers united above into a curved tube enclosing the bifid stigma; capsule ovoid or ellipsoidal, from 5 to 8 mm. in length, light brown, wholly inferior and enclosing numerous brownish, oblong and coarsely reticulate seeds; odor slight and irritating; taste strongly acrid.

Powdered Lobelia. � Dark green; fragments of seed-coat composed of more or less polygonal cells with thick, yellowish walls; occasional non-glandular hairs, elongated-conical, from 0.30 to 1.11 mm. in length; fragments of stem with tracheae showing annular or spiral thickenings or simple pores associated with narrow wood-fibers, the walls of the latter being rather thin, more or less lignified and porous; fragments of epidermis of leaf with elliptical stomata, up to 0.035 mm. in length, and usually with 3 or 4 neighboring cells; pollen grains nearly spherical, from 0.020 to 0.030 mm. in diameter." U. S.

Stems angular, channeled, and furnished with narrow wings; often of a purplish tint; bearing one-celled hairs and the scars of alternate leaves. Leaves irregularly toothed and hairy. Capsules inflated, two-celled, containing when ripe, minute, oblong, reticulated, brown seeds. In transverse section of the stem, laticiferous vessels in the bast. Somewhat irritating odor; taste at first not marked, but subsequently burning and acrid. Ash not more than 12 per cent." Br.

 Pereira found a peculiar acid which he named lobelia acid; besides gum, resin, chlorophyll, fixed oil, lignin, salts of lime and potassium, with ferric oxide. Enders' lobelacrin, according to Lewis (P. J, 1878, viii), is a mixture of lobeline lobelate, with lobelic acid. Lloyd has isolated a crystalline neutral principle (Ph. Bund., 1887, 32) which melts at 225 C., to which he gave the name inflatin. It does not appear to have any therapeutic value. According to Procter the seeds contain a much higher percentage of lobeline than the rest of the plant; from the whole plant he obtained a yield of one-fifth of one per cent. The alkaloid appears to be a rather unstable body, being decomposed by boiling temperature as well as by the caustic alkalies. Vanderkleed and E'we (Proc. P. P. A., 1916, p. 276) propose a method for assaying this drug and its preparations.

Uses. � Lobelia is said to have been used as a medicine by the aborigines of America, but was first brought into general professional notice by Cutler, of Massachusetts. The leaves or capsules, chewed for a short time, occasion giddiness, headache, general tremors, and ultimately nausea and vomiting. When swallowed in the full dose, the medicine produces speedy and severe vomiting, attended with continued and distressing nausea, copious sweating, and great general relaxation. When toxic doses are taken, these symptoms are very severe, and have added to them burning pain in the fauces or esophagus, progressive failure of voluntary motion, rapid, feeble pulse, fall of temperature, and finally collapse with stupor or coma; in some cases convulsions precede death. Death has often resulted from its empirical use. Its poisonous effects are most likely to occur when, as sometimes happens, it is not rejected by vomiting.

In large quantities lobelia has a paralyzing effect on the peripheral motor nerves like that of curare, but this action plays little role in its therapeutic usefulness. Edmunds (A. J. Phys., 1904, xi, p. 80) finds that the chief effect is upon the sympathetic ganglia like nicotine, first stimulating and secondarily depressing.

During the primary stage of stimulation there is increased flow of saliva, dilation of the pupil, constriction of the blood vessels, slowing of the pulse, and other evidences of sympathetic excitation. The slowing of the pulse at first more than counterbalances the vascular constriction, and the blood pressure is usually lowered; later, however, the pulse becomes very rapid and the blood pressure high.

The vomiting appears to be due to an action upon the emetic center. In the secondary stage of poisoning the pupil is contracted, salivary secretion cheeked, respirations slow, and the blood pressure falls. Wieland and Mayer (A. E. P. P., 1922, xcii, 195) state that pure lobeline does not excite either the emetic center nor the sympathetic ganglia, nor does it have any marked action on the vagus; they find its chief action is as a respiratory stimulant. These results are, in a measure, confirmed by the work of Behrens and Pulewka (B. K. W., 1924, iii, 1677) who report a beneficial action on the respiration in poisoning by carbon monoxide. According to Muto and Iwakawa (A. E. P. P., 1910, Ixii), lobeline is a primary stimulant to the respiratory center, the failure in respiration which occurs after toxic doses being due to its paralytic effect on the phrenic nerve. According to Dixon and Brodie (J. P., 1903, xxix), it causes a relaxation of the bronchial muscles which may, however, be preceded by a short stage of constriction.

As an emetic lobelia should never be employed. Its most important use in medicine is as a nauseating expectorant in bronchitis, especially when associated with bronchial spasm. Large doses will sometimes cause complete cessation of the asthmatic paroxysms, but it is more commonly employed between the paroxysms for its combined expectorant and antispasmodic influence.

By the eclectics lobelia is used in a host of convulsive and inflammatory disorders, including epilepsy, tetanus, diphtheria, and tonsillitis.

The tincture affords the most eligible mode of administration; in asthmatic cases it may be given in doses of fifteen minims (0.9 cc.) every hour until an effect is produced. Numes (T G., 1889) asserts that he has used lobeline in a number of cases of asthma with most excellent results in doses of from three-fourths of a grain to six grains a day; but it can scarcely be doubted that he had a very impure alkaloid, and that such doses of a pure sample would be highly dangerous. There is on the market a preparation stated to be alpha-lobeline which is recommended as a respiratory stimulant in doses of one-twentieth to one-sixth of a grain (0.003-0.01 Gm.).