Botanical name: 

The leaves and tops of Marrubium vulgare, Linné (Nat. Ord. Labiatae). Europe; naturalized in America. Dose, 5 to 60 grains.
Common Names: Horehound, Hoarhound.

Principal Constituent.—A bitter principle marrubiin (C30H43O6)
Preparations.—1. Specific Medicine Marrubium. Dose, 1 to 60 drops.
2. Syrupus Marrubii Compositus, Compound Syrup of Hoarhound. Dose, 1 to 4 fluidrachms.
Specific Indications.—Chronic irritation of the bronchial membrane with cough and catarrh.

Action and Therapy.—Hoarhound is a stimulating expectorant and tonic, and is adapted to both acute and chronic irritation of the larynx and bronchial tract, and gives added power to respiration. In small doses it is a gastric tonic of considerable value, but given too freely it will act as an emetic and cathartic. A hot infusion is diaphoretic; a cold infusion, diuretic. Hoarhound, usually in the form of a syrup, is useful in hoarseness, coughs, and colds that do not clear up rapidly, chronic bronchial catarrh, and humid asthma. The specific medicine may be used in atonic dyspepsia, especially when associated with bronchial debility. The compound syrup is an agreeable and efficient expectorant for chronic cough. Hoarhound candy is a popular remedy for irritation of the throat with cough.

The Eclectic Materia Medica, Pharmacology and Therapeutics, 1922, was written by Harvey Wickes Felter, M.D.