In vitro Studies for Vicks Inhaler’s Duration of Action
To test the sustained release of aromatics in VapoRub, analytical in vitro studies3 were conducted and showed the presence of VapoRub’s aromatic over an 8 hour period. Using GC-MS, aromatics (menthol, eucalyptol and camphor) were detected in the headspace above VapoRub immediately after application to the glass tile. The levels of aromatics in the headspace above VapoRub gradually decrease after initial application, from a level of 65% after 30 minutes to 13% at 8 hours. For the control solution, after 30 minutes, only 7% remained and after 1 hour, the aromatics were no longer detectable. This data indicates VapoRub’s petrolatum base enables the sustained release of aromatics over time. A description of the odor character was also recorded by trained olfactive assessors. The olfactive assessment showed good agreement with the GC-MS data that the odour for VapoRub was detectable and considered ‘typical’ over the 8 hour time period.
In addition, a series of pre-weighed polyethylene dishes were filled VapoRub samples, leveled with a spatula and weighed. The samples were placed in a circulating air oven maintained at 35oC. Individual samples of each formula tested were withdrawn from the oven after 1, 2, 3, 4, 6 & 8 hours exposure. After removal from the oven, the samples were immediately re-weighed before being taken for analysis of the principal aromatics (camphor, menthol and eucalyptus oil). At 8 hours, more than 96% by weight of the aromatic entity remained on the tested surface (menthol=98%, Camphor=95.8%, Eucalyptus=93.8%, Total=96.1%).
VapoRub has sustained release of aromatics over an 8 hour period, over a typical sleep period. After 8 hours, a typical VapoRub odour is maintained, without loss of overall character. These data suggest that the active ingredients in VapoRub would be available to be inhaled for the treatment of nasal congestion over an 8 hour period.
Vicks Inhaler’s mechanism of action
Nasal congestion (or “stuffy nose”) is an important symptom/ sign during common cold. Contrary to the common belief that excess mucus is the primary cause of a stuffy nose, it is in fact the inflammation of the nasal lining that leads to nasal congestion4. Upper respiratory tract infections and allergic rhinitis are associated with a significant degree of mucosal inflammation, which induces vasodilatation, increased nasal blood flow, and increased vascular permeability. The resulting engorgement of venous sinusoids and swelling of the turbinates results in a physical reduction in the size of the nasal passages that restricts airflow and is experienced by the patient as nasal congestion5. Witek JT et al6 in an epidemiologic study of 226 common colds found that nasal congestion was the most frequently reported symptom and that nasal congestion was the most bothersome symptom during days 2-5.
VapoRub contains a combination of the active ingredients camphor, L-menthol and eucalyptus oil. It is presented as a petroleum-based ointment (petrolatum) to be applied topically to the chest, back and neck. When rubbed on the skin, VapoRub’s actives are evaporated by the body temperature and inspired into the airways. The therapeutic effects are exerted by interaction of the vaporized essential oils with the receptors located in the airways.
Camphor, L-menthol and eucalyptus oil have been assessed as treatment options for nasal congestion, with early investigation being reported in animal models7. Burrow A et al8 demonstrated the subjective effects of the individual active ingredients in Vicks VapoRub in human subjects. Menthol, eucalyptus and camphor all induced feelings of nasal cooling and increased airflow in both healthy volunteers and patients suffering from common cold.
In conclusion, both clinical data and in vitro results show that Vicks Inhalers can provide “Up to 8 hours relief”.