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Editors Selection IGR 8-4

Medical Treatment: Extended delivery by contact lens

Comment by Tina Wong on:

55170 In vivo performance of a drug-eluting contact lens to treat glaucoma for a month, Ciolino JB; Stefanescu CF; Ross AE et al., Biomaterials, 2014; 35: 432-439

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Ciolino et al. focus on the development and evaluation of a latanoprost- eluting contact lens (CL) for glaucoma treatment.

In the formulation development phase, the authors investigated the drug release from contact lens formulations of different PLGA compositions and varied thickness. They found that the release kinetics were dependent on thickness but independent of PLGA composition. The thicker films displayed a larger burst drug release. However, since the cumulative percentage release from the CLs is not reported, the total amount of drug loaded that has been released in 28 days is unknown.

Achieving one month release from the CL is a key novelty claimed by the authors. Hence it would be important for additional release studies to further verify this as it is not clear whether the drug release was carried out in 'infinite sink conditions'. This is an important consideration since if release equilibrium is not met, the data can be easily misinterpreted, resulting in inaccurate conclusions. In a recent paper, Tieppo et al. studied drug releasing CLs, and reported that apart from drug solubility, the release rate is sensitive to volume of drug release and drug concentration in bulk fluid.¹ The release reported by Ciolino et al. was performed in a release medium with approximately ten times the drug solubility. Hence, the authors need to evaluate the release in different volumes to ensure that the slow subsequent release is not due to over dilution and limited detection of drug in the medium.

The in-vivo performance of the latanoprost-eluting CLs was evaluated based on the latanoprost concentrations in the aqueous humor. Latanoprost-eluting contact lenses achieved comparable in-vivo performance (in terms of drug concentration) when compared to topical administration of latanoprost solutions.

Changing a CL every 28 days does not seem to be a very attractive alternative to eye drops for glaucoma patients

Although the authors concluded that their drug-eluting CL could be potentially used for glaucoma treatment, there was no mention of any possible disadvantages or limitations of this system. These include consideration of presence of ocular surface disease or dry eye that is common to chronically medicated glaucoma patients, thickness of the film rubbing on the corneal surface with potential discomfort of the thicker CL, opacity of the CL from the loaded drug, which may pose a problem during pupillary movement. CL as a drug delivery system may work better for short-term treatment indications, but changing a CL every 28 days does not seem to be a very attractive alternative to eye drops for our glaucoma patients.

Further studies are needed to evaluate the true value of this technology for treating glaucoma.

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