Topical administration of ambroxol eye drops augments tear secretion in rabbits

Purpose: To investigate if topical administration of ambroxol promotes tear secretion and to compare with Diquas ophthalmic eye drop. Methods: Two consecutive studies were conducted using sixteen (32 eyes) New Zealand White rabbits. The first study compared the efficacy of ambroxol hydrochloride (0.05%, 0.2%, and 1.0%) on tear and mucin secretion when administered twice daily. Tear secretion was assessed by Schirmer test I and mucin production by conjunctival impression cytology and PAS stain. The second study compared 0.2% ambroxol hydrochloride with Diquas. A human goblet cell line and human conjunctival tissue were used to test the effect of ambroxol hydrochloride on the expression of aquaporin 5 (AQP5) and MUC5AC, using reverse transcriptase-quantitative polymerase chain reaction and immunoblotting. Results: All three concentrations of ambroxol hydrochloride demonstrated significant efficacy on tear stimulation within 2 weeks of treatment and total mucin component appeared increased. When administered topically twice daily, 0.2% ambroxol hydrochloride was more effective in augmenting tear secretion than Diquas. With 24 h of treatment, 5 μM of ambroxol hydrochloride upregulated AQP5 and MU5AC mRNA and MUC5AC protein in a goblet cell line. When tested on preserved human conjunctiva tissue, a trend of increased production of MUC5AC protein was seen (P = 0.26). Conclusion: Ambroxol is effective in augmenting tear secretion at the ocular surface in rabbits. With actions desirable of a candidate dry eye drug, further investigation of ambroxol and related compounds is warranted to explore their value toward clinical application. [Figure not available: see fulltext.]