Effects of Oral Mucolytics on Tear Film and Ocular Surface
Status:
Completed
Trial end date:
2011-10-01
Target enrollment:
Participant gender:
Summary
Ambroxol is a metabolite of bromhexine and possesses mucokinetic and secretolytic properties
that are also found in mucolytic agents.1 Ambroxol has been used for decades for the
treatment of respiratory disorders associated with excessive mucus, including chronic
inflammatory pulmonary conditions, bronchitis, and pneumonia.2,3 The drug changes the
biophysical properties of secretions by degrading the mucin polymers, deoxyribonucleic acid,
fibrin in airway secretions, and by generally decreasing viscosity.4 In addition, ambroxol
increases cyclic nucleotide (cAMP or cGMP),5 which can theoretically increase tear
secretion.6 Many systemic medications, such as antihistamines, antidepressants, diuretics,
acne drugs, and certain blood pressure medicines can cause or exacerbate a dry eye.7,8 On the
other hand, several topical medications, including mucolytics such as ambroxol and
bromhexine, may be used to treat tear-deficient dry eyes by promoting lacrimal gland
function.9 However, the effects of mucoactive agents on the tear film have not been
investigated systemically, and mucoactive agents may have a disturbing effect on the tear
film because they modify mucin.10,11 The tear film is composed of 3 unique layers, including
the outermost lipid layer, the middle aqueous layer, and the innermost mucus layer; this
structure enables it to perform many functions.12 The lipid layer acts as a barrier to
prevent tear film evaporation, and the aqueous layer supplies oxygen and important nutrients
to the cornea.13 The mucin layer, secreted mostly by conjunctival goblet cells, coats the
corneal surface rendering it hydrophilic, and anchors the tear film to the corneal surface.14
Deficiencies in the amount of tear production or alteration in tear composition can lead to
ocular surface disease.15 Although many studies have focused on aqueous-deficient dry eye
syndrome,16-18 the effect of mucin layer defects on the tear film has not been thoroughly
studied. Furthermore, very few reports have determined the effects of oral mucolytic agents
on the tear film and ocular surfaces, although a study has reported that filamentary
keratopathy was treated with debridement of filaments and application of topical mucolytic
agents such as acetylcysteine eyedrops. In the present study, we investigated the effects of
oral ambroxol on tear film and ocular surface.
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