Side Effects, Dosage

Marrubium vulgare-white horehound or horehound-is a member of the mint family. This wild herb is indigenous to Europe and Morocco. The woolly, hairy (hoary) leaves and white flowers have been used in herbal medicines.

Uses and Benefits

Horehound is used mainly as an expectorant and antitussive; it has been employed as therapy for coughs, bronchitis, respiratory infections, and sore throats, and used as a tonic. It has also been taken for cardiac arrhythmias and diabetes; as a bowel and uterine stimulant; for loss of appetite and flatulence; and externally for sores and wounds. Horehound is alleged to have antioxidant, anti-inflammatory, vasodilator, and diuretic properties.

Horehound may have been used as a bitter confection or food since ancient times. It was chosen as one of the bitter herbs (maror) of the Jewish Passover feast and is still used in confectionary, teas, ales, and other items as a bitter flavor.

Pharmacology

White horehound contains flavonoids (such as quercetin) and diterpenes, including the lactone premarrubiin which is a precursor of the bitter marrubiin. It also contains alcohols (e.g., marrubenol, marrubiol), mucilage, saponins, and the alkaloids betonicine and stachydine; a number of less important chemicals have also been identified. It is claimed that marrubinic acid works as an appetite stimulant and as a choleretic. Horehound, like other bitter substances, may function as a nonspecific expectorant by stimulating the gastro-pulmonary mucokinetic reflex’y, It has demonstrated hypoglycemic effects in rabbits; this may support its use as an antidiabetic medicine in Mexico.

Clinical Trials

There are no clinical trials that demonstrate the various alleged medical uses of horehound or its main constituent, marrubiin.

Adverse Effects

The herb appears well tolerated in usual doses. However, some individuals may experience difficulty with its bitter quality. Large doses cause nausea and vomiting, and have a laxative effect.

Side Effects and Interactions

No drug interactions are recognized.

Cautions

It has not been proved to be safe in pregnancy, but no restrictions are known during lactation.

Preparations & Doses

Horehound can be prepared in liquid extracts and teas, and is commonly found in tablet form, such as medicinal candies or throat pastilles. The usual therapeutic dose is 4.5 g/day of the herb, or 30-100 ml of the juice; dosing is recommended three times a day.The taste may need to be disguised to make it palatable.

Summary Evaluation

Horehound may have minor expectorant properties since, in with all bitter agents, it may stimulate the gastropulmonary expectorant reflex. However, it has not been evaluated dinically, and it cannot be recommended for serious or persistent spiratory disorders. Other alleged health benefits lack evidence. Nevertheless, this ancient herb remains popular for sore throats other minor conditions.

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