Research indicates efficacy of contact lenses as delivery option for anti-allergy drug

Most lenses studied matched or exceeded the usual dose administered via eye drops.

Issue: October 2012

Uptake and release of ketotifen fumarate from daily wear contact lenses may be a feasible option for patients suffering from allergic conjunctivitis, according to a study.

Fourteen different commercially available contact lenses were investigated to determine the uptake and delivery of ketotifen fumarate (KF): five frequent-replacement silicone hydrogels (lotrafilcon B, balafilcon A, comfilcon A, glayfilcon A and senofilcon A), three conventional hydrogels (etafilcon A, polymacon and alphafilcon A), four daily disposables (nelfilcon A, omafilcon A, etafilcon A and ocufilcon B) and two silicone hydrogel daily disposables (narafilcon A and filcon II 3). The lenses were soaked for 24 hours in 6 mL of 0.025% KF loading solution. After the 24-hour period, the lenses were placed in vials of borate buffered saline, and drug release was monitored for 24 hours.

The majority of lenses were able to match or exceed the total amount of KF commonly administered to the eye using twice-daily dosing eye drop formulations (0.025%).

“If one were to use the simple ‘soaking’ technique with commercially available unmodified lenses, like we did to load ketotifen, one would most likely have to use the lens in a daily wear/daily disposable type of modality,” Alex Hui, OD, the study’s coauthor, said in an interview with Primary Care Optometry News. “If extended release and overnight wear are of interest, silicone hydrogel materials would be the clear cut choice to allow sufficient oxygen transmission and prevent any hypoxic complications.”

Etafilcon A, ocufilcon B and balafilcon A showed the greatest uptake and release after 24 hours. All possess ionic polymers and contain a relatively large percentage of water, “suggesting a role in the ionic charge of the material in ketotifen uptake and release,” the authors wrote.

All of the drug-loaded contact lenses displayed a steep release of KF within the first hour or two but then no longer release a significant amount of the drug thereafter, reaching a release plateau from 1 to 3 hours.

“The absolute amount of drug loaded or reloaded is not the main issue; rather it is more about finding ways to increase the release time of the drug,” Hui said. “People have already started to address this issue with such techniques as molecular imprinting and diffusion barriers, and it is likely that a combination of these techniques will be used in the future modification of these materials to tailor release times.”

Hui said that practicing optometrists should start thinking of contact lenses as a potential future drug delivery system for the eye because eye drops have many drawbacks as a delivery system, including poor residency time on the ocular surface, limited drug penetration and poor patient compliance. – by Cheryl DiPietro 

References:

Soluri A, Hui A, Jones L. Delivery of ketotifen fumarate by commercial contact lens materials. Optom Vis Sci. 2012;89(8):1140-1149.

For more information:

Alex Hui, OD, can be reached at the University of Waterloo, 200 University Avenue West, Waterloo, ON, N2L 3G1, Canada; alex.hui@uwaterloo.ca.
Disclosure: The study authors have no relevant financial disclosures.