Modeling Ophthalmic Drug Delivery by Soaked Contact Lenses

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• 作者：Chi-Chung Li and Anuj Chauhan
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2006
• 出版时间：May 10, 2006
• 年：2006
• 卷：45
• 期：10
• 页码：3718 - 3734
• 全文大小：440K
• 年卷期：v.45,no.10(May 10, 2006)
• ISSN：1520-5045

文摘

Approximately 90% of all ophthalmic drug formulations are now applied as eye drops. While eye drops areconvenient and well-accepted by patients, ~95% of the drug contained in the drops is lost due to absorptionthrough the conjunctiva or through the tear drainage. Ophthalmic drug delivery via contact lenses is moreeffective because it increases the residence time of the drug in the eye and leads to a larger fractional intakeof drug by the cornea. In this paper, we model the drug release from the contact lens into the pre- andpostlens tear films and the subsequent uptake by the cornea. The motion of the contact lens, which is drivenby the eyelid motion during a blink, enhances the mass transfer in the postlens tear film (POLTF). We useregular perturbation methods to obtain the Taylor dispersion coefficient for mass transfer in the POLTF. Thediffusion of drug in the gel is assumed to obey Fick's law, and the diffusion in the gel and the mass transferin the POLTF are combined to yield an integro-differential equation that is solved numerically by finitedifference. Two extreme cases are considered in this paper. The first case corresponds to a rapid breakup ofthe prelens tear film (PLTF) that prevents drug loss from the anterior lens surface into the PLTF. The secondcase corresponds to a situation in which the prelens tear film exists at all times and, furthermore, the mixingand the tear drainage in the blink ensure that the concentration in this film is zero at all times. These twocases correspond to the minimum and the maximum loss to the prelens tear film and, thus, represent thehighest and the lowest estimations for the fraction of the entrapped drug that diffuses into the cornea. Resultsshow that the dispersion coefficient of the drug in the postlens tear film is unaffected by the release of thedrug from the gel. Furthermore, simulation results show that drug delivery from a contact lens is more efficientthan drug delivery by drops. The fraction of drug that enters the cornea varies from ~70 to 95% for the firstcase (no flux to the PLTF) and from 20 to 35% for the second case (zero concentration in the PLTF). Themodel predicts that delivery of pilocarpine by soaked contact lenses is ~35 times more efficient than deliveryby drops, and this result matches clinical observations.