TITLE:
Analysis of pathomechanisms involved in side effects of menthol treatment in respiratory diseases
AUTHORS:
Silvia Gavliakova, Tomas Buday, V. Manjunath Shetthalli, Jana Plevkova
KEYWORDS:
Menthol; TRPM8; Airways; Treatment
JOURNAL NAME:
Open Journal of Molecular and Integrative Physiology,
Vol.3 No.1,
February
19,
2013
ABSTRACT: Menthol
is frequently used in over the counter medications for common colds and
coughs. It was formerly considered to be under the class of herbal medicine,
but identification of menthol receptor (TRPM8) moved it from the class of
herbal medicine to the molecular pharmacology. It has been documented that
menthol reduces dyspnoea and nasal obstruction via stimulation of nasal cold or
flow receptors. It has also antitussive and antiirritative effect. Menthol can
also induce adverse reactions such as airway irritation, dyspnoea, chest
tightness and potentially respiratory failure, mainly in children. The
mechanisms responsible for adverse reactions of menthol are not known
completely. The adverse reactions of menthol could be due to its effects on
TRPA1 channel, relevant to airway irritation. Higher concentrations of menthol
stimulate TRPA1 channel causing airway irritation. It also increases mucus production
and at the same time reduces cilliary activity leading to mucus stagnation.
As the adverse effects were reported mainly at the night it is supposed that
suppressed cough reflex during sleep potentiated by menthol induced cough
suppression might be responsible for lack of airway mucus clearing and
obliteration of small airways. Adverse effects could also be due to
consequences of reflexes induced by the menthol action on trigeminal afferents,
like apnoea or bronchoconstriction. Menthol is effective in relieving
respiratory symptoms, but cough and cold medications should be used with
caution. Recommendations are low concentrations of menthol used locally
(intranasal) and not combined with camphor or cineole, as they may have
additive effects and should be avoided in children under 2 years. Further data
are necessary to completely elucidate potential risks of over the counter
menthol medication in children but based on the meta analysis of documented
case reports, menthol can be used safely if its contraindications for use are
followed as with any other over the counter medications.