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a medicinal substance that facilitates the expulsion of sputum by intensifying secretion in the bronchial glands or by liquefying the secretion. An expectorant can also work by stimulating contraction of the bronchial musculature.
The mode of action of an expectorant on the musculature and mucosa of the bronchi can be direct or reflexive. Direct-acting expectorants include terpin hydrate, potassium and sodium iodides, the essential oils of eucalyptus and anise, and turpentine. The active principles in essential oils—terpenes and aromatic hydrocarbons—stimulate the bronchial glands. These oils, which also have antiseptic and deodorant properties, can be ingested or inhaled. Sodium bicarbonate and ammonium chloride are mild expectorants that alter the viscosity of bronchialgland secretions by dissolving mucin. A more effective agent is the proteolytic enzyme trypsin, which decreases the viscosity of sputum by depolymerizing the constituent protein molecules.
Expectorants whose mode of action is reflexive are prepared from the medical plants Cephaelis ipecacuanha, Cephaelis acuminata, Thermopsis, and Polygala senega. The alkaloids and saponins in these plants stimulate the receptors of the gastric mucosa and reflexively intensify peristalsis of the smooth musculature of the bronchi as well as secretion from the bronchial glands.
Expectorants are used to treat bronchitis and other inflammatory diseases of the respiratory tract that are accompanied by a cough with a viscous sputum that is difficult to expel.
REFERENCESVotchal, B. E. Ocherki klinicheskoi farmakologii, 2nd ed. Moscow, 1965.
Zakusov, V. V. Farmakologii, 2nd ed. Moscow, 1966.
Mashkovskii, M. D. Lekarstvennye sredstva, 7th ed. Moscow, 1972. Parts 1–2.
V. V. CHURIUKANOV