Hedeoma consists of the dried leaves and flowering tops of American pennyroyal, Hedeoma pulegioides, Pers. (N.O. Labiatae), an annual plant which is common in the Eastern and Middle Western United States, where it is indigenous. The drug is official in the U.S.P. The leaves are opposite and occur on quadrangular branchlets, with numerous spreading hairs; they are short-petioled, oblong-ovate, 15 to 35 millimetres long, thin, obtuse, obscurely serrate, with glandular hairs beneath. Flowers in axillary fascicles, with tubular-ovoid, bilabiate and five-toothed calyx, and pale blue, spotted, bilabiate corolla, containing two sterile and two fertile, exserted stamens. The drug has a strong, somewhat mint-like odour, and an aromatic, pungent taste.
Constituents.—The active constituent of hedeoma is the volatile oil, which contains a liquid ketone identical with the pulegone found in the oil of Mentha Pulegium. (See Oleum Hedeomae.)
Action and Uses.—Hedeoma has gentle stimulant properties similar to those of other aromatic herbs, and is mildly expectorant and diaphoretic. It is used as an emmenagogue, acting reflexly on the uterus by mildly exciting the urinary tract during its excretion; and may also be given in flatulent colic, being administered in powder or as a warm infusion (1 in 20).
Dose.—4 to 8 grammes (60 to 120 grains).