Lobelia, or Indian tobacco, consists of the flowering plant, Lobelia inflata, Linn. (N.O. Lobeliaceae), collected and dried. The plant is in annual herb, indigenous to, and cultivated in, the eastern United States. Lobelia, U.S.P., consists of the dried leaves and tops of L. inflata, collected after some of the capsules have become inflated. The stems, which are abundantly present, are angular and channelled, slightly winged, hairy and greenish in colour in the upper part, but glabrous and often purplish in the lower. The leaves are alternate, ovate, sessile, or shortly petiolate. They have an irregular, crenate-dentate margin, and bear bristly hairs, especially on the under surface. The flowers are not, as a rule, present in the drug, but the capsular fruits are frequently to be found. These are two-celled, and when ripe contain minute, oblong, reticulated seeds. Transverse sections of stem and leaves show laticiferous vessels in the bast. Odour, slightly irritating; taste, burning and acrid. The drug yields about 10 per cent. of ash.
Constituents.—The chief constituent of the drug is the liquid, or white amorphous, alkaloid lobeline, which darkens on keeping; it forms crystalline salts. Other constituents are a neutral, crystalline, inactive body called inflatin, and lobelic acid. Lobelacrin appears to be lobeline lobelate.
Action and Uses.—Lobelia is used for its action in depressing the vaso-motor centre and peripheral vagus, thus producing dilatation of the bronchioles by relaxing the bronchial muscles. Lobeline has an action very closely resembling that of nicotine. It first excites nerve a cells and then paralyses them. The stimulation is pronounced, though transient. Lobelia is given in spasmodic asthma, in the dyspnoea of chronic bronchitis, and in other affections of the air passages; it should not be employed if there is cardiac disease. Lobelia is also an expectorant in laryngeal and bronchial catarrh. Its action in spasmodic asthma is enhanced by combination with sodium iodide or bromide. Large doses are diuretic, cathartic, and emetic; they may cause collapse through medullary paralysis. It is a common ingredient of powders intended to be burnt for asthma (see Pulvis Lobeliae Compositus and Pulvis Stramonii Compositus). For internal use, the tincture and ethereal tincture are administered; some authorities recommend the use of large doses frequently repeated until nausea is produced. In case of poisoning by lobelia, alcohol and ammonia should be freely employed and the stomach evacuated.
Dose.—2 to 6 decigrams (3 to 10 grains).
- Fluidextractum Lobeliae, U.S.P.—FLUIDEXTRACT OF LOBELIA.
- Lobelia, in No. 50 powder, 100; acetic acid (36 per cent.) and water of each a sufficient quantity, to 100. The drug is exhausted by percolation with a menstruum consisting of acetic acid, 11; distilled water, 19. Average dose.—5 decimils (0.5 milliliters) (8 minims).
- Pulvis Lobeliae Compositus, B.P.C.—COMPOUND LOBELIA POWDER. Syn.—Asthma Powder.
- Lobelia, 25; stramonium leaves, 25; Potassium nitrate, 25; oil of anise, 0.1; tea leaves, to 100. Used for asthma, half a teaspoonful or more being burned, and the fumes inhaled several times daily, or as required. Pulvis Stramonii Compositus is a similar preparation.
- Tinctura Lobeliae, B.P., 1885.—TINCTURE OF LOBELIA.
- Lobelia, in No. 40 powder, 12.5; alcohol (60 per cent.), sufficient to produce 100. Add 10 of the alcohol to the drug to moisten it and complete the percolation process. Tincture of lobelia is used in a similar way to the ethereal tincture. Dose.—1/2 to 2 mils (10 to 30 minims).
- Tinctura Lobeliae, P.I.—TINCTURE OF LOBELIA, P.I.
- Strength, 10 per cent. Prepared by percolation with alcohol (70 per cent,).
- Tinctura Lobeliae, U.S.P.—TINCTURE OF LOBELIA.
- Lobelia, in No. 50 powder, 10; alcohol (49 per cent.), to 100. Average dose.—Expectorant, 1 mil (15 minims); emetic, 4 mils (1 fluid drachm).
- Tinctura Lobeliae, Aetherea, B.P.—ETHEREAL TINCTURE OF LOBELIA.
- Lobelia, in No. 40 powder, 20; spirit of ether, sufficient to produce 100. Add 10 of spirit of ether to the drug to moisten it, and complete the percolation process. This preparation is used chiefly as an antispasmodic and expectorant in asthma and bronchitis. Dose.—3 to 10 decimils (0.3 to 1.0 milliliters) (5 to 15 minims).
The British Pharmaceutical Codex, 1911, was published by direction of the Council of the Pharmaceutical Society of Great Britain.