Lobelia inflata is indigenous to the flora of Canada, Kamchatka, and the northeastern United States. It has a long history of medicinal use as a respiratory stimulant, antiasthmatic, antispasmodic, expectorant, and emetic therapy. Well-known to Native Americans, this acrid-tasting plant is also called Indian tobacco. It was also highly touted by the Thomsonians, a group of nineteenth-century health care practitioners sarcastically labeled "lobelia doctors." Herbalists have traditionally combined lobelia with other medicinal plants such as cayenne pepper, lungwort, Ma Huang, or licorice. American Indians historically smoked lobelia as a treatment for asthma. More recently, individuals have smoked dried lobelia herb as a recreational euphoriant drug.

At one time, lobelia was approved by the FDA for use as a major ingredient in antismoking, herbal preparations. Lobelia reportedly alleviated symptoms of nicotine withdrawal during smoking cessation. However, the rationale for doing this was eventually called into question since lobelia possesses many of the same pharmacological properties of nicotine. The crude drug is now considered unsafe both as an antismoking agent and as a treatment for asthma and bronchitis. Many authorities in plant drug research claim that the risk of potential toxicity from the alkaloids present in lobelia outweigh its benefits.

Pharmacological support for the effectiveness of lobelia as a therapeutic agent (other than as a sedative) and euphoriant is weak. Although lobelia has a favorable stimulatory action on the respiratory center, it is metabolized too quickly to be considered an efficacious respiratory analeptic (restorative).

Lobelia is a visually attractive, annual or sometimes biennial herb that grows to a height of 50 cm. It erect, hairy stem is angular, branching at the top, and characteristically green with a tinge of violet. The pale green or yellowish leaves are narrow, lance-shaped, and short-stemmed. They are alternate or oblong, with hairy veins and irregularly toothed margins. The leaves have an acrid taste and a slightly irritating odor. The sparse, small, two-lipped flowers are pale violet-blue outside and pale yellow inside. The flowers grow in a terminal spike on long pedicles in the leaf axils.

Herb (aerial parts), leaves, tops, seeds.

Piperidine-type alkaloids (0.48%): lobeline, lobelanine, lobelanidine, norlobelanine, lelobanidine, norlelobanidine, norlobelanidine, lobinine; bitter glycoside (lobelacrin), chelidonic acid, fats, gum, resin, volatile oil.

Available for oral intake as dried herb and liquid preparations, including tinctures; and for topical use in ointments, lotions, suppositories, and plasters.

Traditional uses: Taken internally for angina pain, bronchitic asthma, chronic bronchitis, particularly spasmodic asthma with secondary bronchitis, and symptoms of smoking withdrawal; applied externally for myositis and rheumatic nodules.

Conditions: Asthma, spasmodic asthma with secondary bronchitis, chronic bronchitis, spastic colon, spastic muscle conditions, pneumonia.

Clinical applications: Respiratory stimulant, spasmolytic, expectorant. 

The pharmacological effects of lobelia are attributed primarily to piperidine-type alkaloid constituents, particularly lobeline. Although lobeline is less potent than nicotine, its actions on the peripheral and central nervous (CNS) systems are similar to those of nicotine. According to other research, however, the principle pharmacological activity of lobeline is not nicotinic agonism. Rather, lobeline may affect CNS activity by altering the dopamine chemistry of the brain. Lobeline has been shown to be more potent than d-amphetamine in blocking dopamine uptake into synaptic vesicles.

In normal doses, lobeline functions as a CNS stimulant that dilates the bronchioles, thereby increasing respiration. However, the initial bronchial dilation is often followed by an adverse effect of respiratory depression, particularly during overdosing.

Lobeline induces reflex stimulation of the respiratory center by acting on the chemoreceptors of the glomus caroticus. This medicinal plant presumably exerts its antiasthma activity by stimulating the adrenal glands to release epinephrine, which in turn binds to beta-2 receptors. The net effect of this physiological property is relaxation of the airways. Lobelia also affects gastrointestinal function by stimulating the vomiting center in the reticular formation of the medulla oblongata at the base of the brain.

In an in vivo experiment, a crude methanolic leaf extract of Lobelia inflata produced antidepressant effects in mice. The active constituent responsible for this activity was identified as beta-amyrin palmitate. In another study, the in vivo actions of beta-amyrin palmitate on central nervous system activity were compared with those of two antidepressant drugs, mianserin and imipramine. Beta-amyrin palmitate (administered at 5, 10 and 20 mg kg/1) produced a dose-related decrease in locomotor activity of mice and had an antagonistic effect on methamphetamine-induced locomotor stimulation.

In addition, beta-amyrin palmitate at these same doses exhibited potentiating action on chemically-induced narcosis in test animals. Beta-amyrin palmitate was milder than mianserin but more potent than imipramine in eliciting the potentiating effect. These findings offer pharmacological evidence for the sedative properties of lobelia. However, since oral preparations of lobeline are metabolized so rapidly that their effects are only transitory, topical applications may be more efficacious.

• Dried herb (infusion or decoction): ¼ to ½ tsp. herb in 8 oz. water, preferably mixed with other herbs; steep 30 to 40 minutes. Take 2 oz. qid. (This method is not preferred because of lobelia's acrid taste.) 
• Liquid extract (1:1 in 50% alcohol): 0.2 to 0.6 ml tid 
• Tincture of lobelia: 0.6 to 2.0 ml 
• Vinegar tincture of lobelia (1:5 in dilute acetic acid): 1 to 4 ml tid 

Some practitioners recommend starting dosage at 7 to 8 drops, adding a drop with every dose. If the patient experiences nausea, cut back the dosage.

Note: Therapy should begin with the use of lower level dosages and increased appropriately depending upon individual patient response.

Both lobelia and its main active principle, lobeline, can produce undesirable symptoms of nausea, vomiting, diarrhea, coughing, dizziness, disturbed hearing and vision, mental confusion, and weakness. All these symptoms resemble toxic reactions to nicotine.

Overdosage of lobelia may cause adverse side effects of shivering, profuse sweating, tachycardia, convulsion, hypothermia, hypotension, coma, and, in extreme cases, death due to respiratory failure. Ingestion of 0.6 to 1 g of lobelia leaves is reportedly toxic.

Note: In cases of acute toxicity from lobelia, atropine (2 mg) should be administered subcutaneously as an antidote.

Lobelia should not be consumed in excessive amounts because of the toxicity of its potent alkaloid compounds. As in the case of nicotine, lobelia and lobeline are contraindicated during pregnancy and lactation.

No clinically significant interactions between lobelia and conventional medications are known to have been reported in the literature to date.

Lobelia has not been designated as an approved herb, or an unapproved herb, by the German Commission E. In the United Kingdom, lobelia (in doses of up to 65 mg per single dose) is on the General Sale List, Schedule 1, Table A. Higher oral doses of up to 200 mg per dose (600 mg per day) and external preparations containing quantities of not more than 10% lobelia are reserved for pharmacy use only in the United Kingdom. Herbal practitioners are exempt from this regulation.

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