This eye-drop formulation can increase the effectiveness of ocular cystinosis treatments by delaying the oxidation rate of cysteamine to increase the shelf life of eye-drop products. Cystinosis is a rare genetic disorder that causes crystalline deposits to accumulate in the cornea, negatively affecting vision. If left untreated, cystinosis can lead to stunted growth, renal failure and blindness. Applying cysteamine eye drops flushes harmful compounds out of eye cells to treat the disease. However, cysteamine drops oxidize when exposed to air, making the drops ineffective a short time after opening the dropper for use. Freezing available cysteamine drop treatments prior to use or sealing them with low-oxygen-permeable materials, such as bromobutyl or aluminum, extends their shelf life. However, neither protects the formulation from air that enters the bottle when administering the drops, making the treatment maximally effective for only about a week after opening.
Researchers at the University of Florida have developed a formulation to slow the degradation rate of cysteamine. Integrating an oxygen-resistant polymer to the formulation combined with floating a hydrophobic antioxidant layer on its surface increases the shelf life of available cysteamine drop treatments to nearly a month after opening.
Formulation to increase the shelf life of available cysteamine treatments for ocular cystinosis
A hydrophobic oil added to cysteamine prevents oxidation of the cysteamine's thiol group. The oil impedes the rate of completion for the redox reaction between oxygen molecules and the compound's active ingredient, which slows the oxidation process. An inorganic polymer present in the eye drop bottle works in conjunction with this protective barrier, increasing the solution's viscosity. The polymer also prolongs contact with the cornea once the formulation enters the eye, increasing bioavailability of non-degraded cysteamine.