Generality
Under the term "expectorants" are grouped all those active ingredients and drugs, phytotherapic or synthetic, capable of promoting the removal of mucus and exudate from the trachea and bronchi.
Purging of mucosal stasis, induced by expectorants, frees the airways, improving the well-being of the patient suffering from bronchitis, colds or other catarrhal diseases of the respiratory tree.
Direct Expectorants
Balsamic, secretolytic, ciliary and mucolytic activity stimulators
Essential oils belong to the category of direct expectorants, which once absorbed orally are absorbed in the intestine and partially eliminated through the respiratory tree. Here, at the bronchial level, they stimulate the serous (tubulo-acinar) glands increasing the aqueous component of catarrhal secretions (they are therefore known as balsamic expectorants); at the same time and at the same level, these substances inhibit the activity of the muciparous goblet glands (they are therefore known as secretolytic expectorants). Overall, therefore, the result is a more fluid and easy to eliminate mucus, thanks also to the stimulation of essential oils on the ciliary activity. This last property is characteristic of the so-called expectorant stimulators of the motility of the secretion, which facilitate the transport of the mucus towards the pharynx, through the stimulation of the ciliary movement; the most famous representatives of this group are the B2-sympathomimetics and theophylline, partly also anticholinergics and benzylamines (Ambroxol type).
Among the secretolytic expectorants, besides the already mentioned essential oils (of eucalyptus, of niaouli, of mint, of lavender, of pine, balsam of Peru), also include the eminine, bromexine and ambroxol.
Another sub-category of direct expectorants is that of mucolytics, active ingredients capable of directly modifying the quality of bronchial mucus. The most famous representative of this category determines a reduction in the viscosity of the mucus, breaking the sulfide bridges that characterize its proteins; we are talking about N-Acetyl-Cysteine. Various proteinases and mercaptoethanesulfonate also act with a similar mechanism of action.
Indirect expectorants
Saponoside drugs
The indirect expectorants act at the gastric level, irritating the mucous membrane of the stomach; this insult results in an indirect stimulus to bronchial secretion, according to a physiological mechanism known as a gastropulmonary reflex. This category includes drugs with saponins, such as ivy, mullein, horehound, primrose, white nettle and licorice (which, on the whole, has a gastroprotective action); less used than in the past, due to the greater side effects, are the polygala, saponaria and ipecacuanana.
Precautions for use
Saponin drugs, by virtue of the above-mentioned mechanism of action, tend to cause nausea and gastrointestinal irritation, especially in the case of prolonged use. At dosages around 10 times higher than those used for expectorant purposes, these herbal remedies become emetic, so much so that they are used to cause vomiting and reduce the absorption of the toxic substance (see ipecacana).
As for the expectorants with essential oils, let us remember that the most effective and safe method of use is the oral one, by ingestion of standardized capsules in the active ingredients. It is not recommended for use in herbal teas for oral use, because the essential oil would float in the aqueous preparation irritating the mucous membrane of the oral cavity; particular care must also be taken in the use by inhalation. These natural expectorants, in concentrated solutions, are typically dispersed in the radiator trays or in the fumigation vaporizers, to the extent of very few drops per liter of water. However, excessive inhalation of vapors can cause allergic reactions, bronchospasm and asthma attacks, especially in the smallest and those predisposed; hence the advice to use hot water, but not hot.
