Lobelia. The leaves and tops of Lobelia inflata Linné (Nat. Ord. Lobeliaceae), collected after a portion of the capsules have become inflated. Indian tobacco. Lobélie enflée, Fr.; Lobelia-kraut, Ger.

Acetum Lobeliae

Vinegar of lobelia. (Lobelia, 10 parts; diluted acetic acid to make 100 parts.) Dose, τη v—3 j. (Not official.)

Tinctura Lobeliae

Tincture of lobelia. (Lobelia, 200 grm.; diluted alcohol sufficient to make 1,000 c. c.) Dose, τη v— 3 j.

Extractum Lobeliae Fluidum

Fluid extract of lobelia. Dose, τη j— 3 ss.

Composition

The effects of lobelia are due to the presence in it of a peculiar alkaloid—lobeline. This principle is oily in consistence, has a pungent, rather acrid taste, a tobacco-like odor, and is strongly alkaline in reaction. It is slightly soluble in water, but more freely soluble in alcohol and ether. It combines with acids to form crystallizable salts, which are soluble in water and in alcohol. The active principle—lobeline—is combined in the plant with lobelic acid.

Antagonists and Incompatibles

The caustic alkalies decompose lobeline; hence these are incompatible. The depressing effects of lobelia on the circulation are counteracted by digitalis, belladonna, ergot, and other vaso-motor excitants, by alcohol, ether, ammonia, etc.; on the nervous system of animal life, by strychnine, picrotoxin, thebaine, etc.

Synergists

All of the motor depressants increase the effects of lobelia.

Physiological Actions

The taste of lobelia is pungent and acrid, and it persists for a long time in the fauces. The leaves chewed excite a very abundant flow of saliva, and soon cause a feeling of epigastrio depression and nausea, with giddiness and headache. The preparations of lobelia administered by the stomach produce, in considerable doses, a degree of nausea and depression which amounts to anguish. An abundant outpouring of gastric mucus takes place, and vomiting ensues, with great straining and distress. The action of the heart is enfeebled; headache and vertigo are experienced; a profuse sweat breaks out on the surface of the body; the intestinal canal is relaxed, and the discharge of urine is increased. When a lethal dose is taken, especially if vomiting do not occur, the effects are chiefly expended on the nervous system of animal life. Muscular weakness and trembling, shallow respiration, coldness of the surface, feeble circulation, insensibility, and sometimes convulsions, have occurred. Death ensues from paralysis of the muscles of respiration—the action of the heart continuing after respiration has ceased. The insensibility is doubtless produced in the same way as by tobacco, and the cerebral effects are not the result of a direct action of the poison.

According to the investigations of Ott, lobeline, in moderate doses, first "increases the blood-pressure by acting as an excitant on the peripheral vaso-motor nervous system." This primary effect is not of long duration, a fall in the blood-pressure soon occurs, the peripheral circulation is so embarrassed from weakened power of the heart, and obstructed pulmonary circulation, that oxygenation of the tissues is rapidly impaired, and a marked reduction of temperature takes place. Lobeline affects chiefly the motor nervous system, and especially the medulla oblongata and its respiratory center (nucleus of pneumo-gastric).

Therapy

Lobelia is much employed by the self-styled physio-medical practitioners as a "sanative agent." The great quantity of mucus discharged from the stomach under its emetic action is considered by them a proof of its power as an eliminating agent. As an emetic, lobelia is entirely too harsh and depressant to justify its use for this purpose. In habitual constipation, dependent on atony of the muscular layer of the bowel and deficient secretion of the mucous membrane, good results are sometimes obtained by small doses of the tincture—ten minims—administered at bedtime. Impaction of the caecum, when inflammation has not occurred, may be removed, and the bowels induced to act, by small doses, frequently repeated, of the tincture of lobelia (two drops every hour). This remedy can be used when purgatives would produce serious mischief. An infusion of lobelia as an enema has succeeded in relieving strangulated hernia, intussusception, and fecal impactions. This use of the agent is the same as for the corresponding administration of tobacco; it is much safer than tobacco, and can be made to produce as decided therapeutic effects.

Unquestionably the most important application of lobelia is to the treatment of the asthmatic paroxysm. It gives relief in a few minutes to violent attacks of spasmodic asthma, and it sometimes happens that the relief is permanent. Frequent repetition of this remedy in the same individual, however, lessens its effects, and it may finally cease to afford any relief. To be effective in asthma, a tea spoonful dose of the acetum or tincture must be administered every fifteen minutes until nausea is induced. Free expectoration and abundant gaseous eructations take place, and the breathing soon becomes easy and calm. The efficiency of lobelia is increased by the addition of iodide and bromide of ammonium. Rx Tinct. lobeliae, oz j; ammonii iodidi, 3 ij; ammonii bromidi, 3 iij; syrup, tolutan., oz ij. M. Sig.: A tea-spoonful every one, two, three, or four hours. The hydrobromate of lobeline is the most efficient preparation for treating the respiratory neuroses, and certain cardiac affections, such as pseudo-angina pectoris.

Whooping-cough, especially after the cessation of the catarrhal stage, has been treated successfully by lobelia, but we now possess other agents more effective and less disagreeable in action. Lobelia is, however, an excellent expectorant. It is adapted to cases in which the cough is dry, resonant, and spasmodic. It succeeds best in those who have attacks of cough with spasmodic difficulty of breathing, and who get up a little tough mucus after long and painful paroxysms of coughing. A lobelia-emetic will cut short an attack of spasmodic croup, but it is too harsh and dangerous a remedy to be employed for this purpose; but it is less dangerous than is generally supposed. In consequence of the fear which invests it, the doses given are often insufficient to effect the good results it may induce; and this is true of the various catarrhal conditions of the respiratory mucous membrane especially.

Authorities referred to:

Ott, Dr. J. Note on the Action of Lobelina on the Circulation. (Reprinted from the Boston Medical and Surgical Journal.)

Porcher, Dr. Francis Peyre. Resources of the Southern Fields and Forests, p. 438.