Fig.3: Comparison between drug inhalation and exhalation.
Looking for a molecule that meets the requirement to be eliminated via the lung, we may search among monoterpenes, whose chemical and pharmacological characterizations are well known. The 1,8-cineole eucalyptol is the main monoterpene of the essential oil of eucalyptus. The EMA community herbal monograph on eucalyptus essential oil has established a dose regimen of 200 mg orally up to 5 times/day, and its safety has been adequately assessed. It has been reported to have a large spectrum of antimicrobial effect against several type of bacteria, viruses and fungi, which is assumed to be a nonspecific pharmacological effect given its phenolic chemical characteristics. A specific in vitro investigation has highlighted the antiviral properties of an aerosolized solution of eucalyptol on nebulized viruses (Usachevet al. , 2013), confirming the antiviral properties already described (Astani et al., 2010). Furthermore, its anti-inflammatory effect in the lung has been well characterized, and specific clinical trials of its traditional use have highlighted its efficacy and safety in asthmatic patients. All these pharmacological characteristics of this monoterpene could make it a candidate to test for the treatment of COVID-19, and its use as a prophylactic or when the viral load is particularly low is also hypothesized. A further advantage is given by the great flexibility of the molecule, which can be used both by inhalation and orally. Another point to consider is the great availability of different monoterpenes, of which 1,8 cineole can be considered a representative, with similar characteristics that can be taken into consideration in a more detailed scientific analysis and for subsequent use in therapy.
The use of naturally derived substances in this particular emergency situation is also reflected in recent clinical trials that focus on a possible role of traditional Chinese medicine (TCM) in support of standard therapy. Some Chinese guidelines have described the use of traditional herbal medicine for prophylactic purposes (Jin et al., 2020). Furthermore, the recent precious gift made by the People’s Republic of China to Italy as emergency support contained TCM products (Ansa, 2020).