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Use of UV blocking contact lenses lowers degradation of drug
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Degradation of dexamethasone in drug eluting contact lenses was minimized by using vitamin E or a UV blocking contact lens, according to a study recently published in Optometry and Vision Science.
Hsu and colleagues loaded contact lenses with dexamethasone and investigated ways to stabilize the drug.
Researchers utilized two commercial silicone hydrogel lenses, narafilcon B and lotrafilcon B (1SaveOnLens) for the study. To load the contact lenses, they soaked them in 3 mL of 0.066 mg/mL dexamethasone (Sigma-Aldrich Chemicals) in phosphate-buffered saline (Mediatech) for 7 days. Researchers also loaded the lenses with vitamin E. They used a UVB-10 transilluminator (Ultra-Lum Inc.) in a constant-temperature, humidified chamber and then eluted the remaining drug in order to study degradation.
Results showed that 1% of dexamethasone degraded in class 1 UV blocking contact lenses after 20 hours, compared to 85% in non-UV blocking lenses. Additionally, researchers reported that the use of vitamin E reduced fractional degradation to 30%.
"There is a growing interest in drug-eluting devices for extended delivery of ophthalmic drugs," the authors wrote. "Several ophthalmic drugs such as dexamethasone are unstable and, thus, extended release may not be useful unless the encapsulation method also provides a stabilizing effect."
They concluded: "This study shows that the degradation rates of drug loaded in contact lenses are much lower than the rates in solution. Furthermore, the degree of UV blocking significantly impacts the degradation rates, with negligible degradation in a class 1 UV blocking lens. Even in a non-UV blocking lens, the degradation rates are significantly lower than those in solution, and further reduction in the degradation rates can be achieved by incorporating vitamin E into the lenses."
Researchers noted that vitamin E was beneficial for several purposes – release duration, degradation rate and eye protection.
They recommended that future studies be conducted under in vivo conditions to assess typical wear conditions. – by Chelsea Frajerman Pardes
Disclosure: The authors reported no relevant financial disclosures.
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