Lobelia-Lobelia.-The dried flowering herb of Lobelia inflata. Imported from North America.

Characters.-Stem angular; leaves alternate, ovate, toothed, somewhat hairy beneath; capsule ovoid, inflated, ten-ribbed; herb acrid. Usually in compressed rectangular parcels.

Composition.-Lobelia contains an active principle, lobelina, an oily, liquid, and volatile alkaloid, with a pungent taste, and an odour like tobacco. It forms salts with acids. Lobelic acid is united with the lobelina.

Incompatibles.-The caustic alkalies, which decompose lobelina.

Preparations.

1. Tinctura Lobeliae

Tinctura Lobeliae. 1 in 8 Proof Spirit. Dose, 10 to 30 min.

2. Tinctura Lobeliae Aetherea

Tinctura Lobeliae Aetherea. 1 to 8 Spirit of Ether. Dose,

10 to 30 min.

Action And Uses. 1. Immediate Local Action And Uses

Lobelia is a gastro-intestinal stimulant; in large doses an irritant, causing vomiting, pain, purging, and the ordinary symptoms of depression. It is not to be used as an emetic, but is sometimes useful in obstinate constipation.

2. Action On The Blood, And Specific Action And Uses

The active principles of lobelia appear to enter the blood and tissues, where severe specific effects are produced by free doses, including general depression, muscular tremors and weakness, giddiness, headache, failure of the heart and breathing, and cold perspiration: a condition resembling collapse. The exact mode of the action of the drug is not known, but it appears to depress the convolutions secondarily only; to lower the activity of the motor centres in the cord, and cause muscular relaxation: to depress the respiratory centre, and relax the bronchial muscles; and to diminish the force of the heart and the tension of the vessels, after brief increase of the latter. Lobelia kills through the respiratory centre, like its ally, tobacco, and not through the heart.

Lobelia is a favourite remedy with some practitioners for the paroxysm of asthma, for which it should be given at the commencement in doses of 1 drachm of the Tincture, repeated every fifteen minutes till nausea is produced. In 10 min. doses it is a useful addition to expectorant mixtures for bronchitis with spasm and very scanty tough sputum.

3. Remote Local Action And Uses

Lobelina is probably excreted by the kidneys and skin, and acts as a diuretic and diaphoretic. Except indirectly, these effects are not taken advantage of in medicine.