Optimizing Release from Reservoir Microcapsules
Hoang, David; Liu, David; Chen, Jennifer; Siu, Vince
Cytomegalovrius (CMV) retinitis is a common symptom of vision loss found in 20-30% of all acquired immunodeficiency syndrome (AIDS) sufferers. While there are no drugs that can cure permanent retinal damage by CMV, the drug ganciclovir has demonstrated efficacy against human cytomegalovirus infections and has been considered a first-line therapy in the treatment of sight-threatening cytomegalovirus infection in immune-compromised patients. The FDA-approved Vitrasert? implant, which is inserted at a localized region of the eye, is the current method of delivering ganciclovir intraocularly to patients with CMV. The Vitrasert? is a disc-like reservoir microcapsule that encapsulates ganciclovir in a polymer-based system. Maintaining a constant level of drug in the infected eye region is an important requirement in the design of this implant. The more constant the rate of drug release from the microcapsule, the more effective the drug will be. The objective of our model is to measure the diffusion of the ganciclovir release from the Vitrasert? into the surrounding tissue and to ensure toxic levels of the drug is not sustained. To accomplish this objective, the implant is simplified via axis-symmetry from a 3-D cylinder into a 2-D rectangle with homogeneous material properties, while the skin is reduced to a quarter-circle around our capsule. With our model, we are able to optimize the characteristics of the microcapsule to facilitate near constant drug release, which would be beneficial for many pharmaceuticals working with drug release from reservoir microcapsules.
cytomegalovirus retinitis; ganciclovir; Vitrasert?; microcapsule; constant release rate