Punctal plug delivery system could improve adherence among patients with glaucoma

November 10, 2008

A novel drug delivery device using a punctal plug to provide pressure-lowering medication to patients with glaucoma could improve compliance and reduce the amount of medication required to maintain pressure control, said Richard A. Lewis, MD, a cataract surgeon and glaucoma specialist based in Sacramento, California.

A novel drug delivery device using a punctal plug to provide pressure-lowering medication to patients with glaucoma could improve compliance and reduce the amount of medication required to maintain pressure control, said Richard A. Lewis, MD, a cataract surgeon and glaucoma specialist based in Sacramento, California.

The Latanoprost Punctal Plug Delivery System consists of a latanoprost-eluting core inserted into a punctal plug. The core is filled with varying concentrations of latanoprost (Xalatan, Pfizer Ophthalmics) and applied to a punctal plug that is placed in an inserter and implanted in the puncta for delivery of medication.

In a pilot study conducted in Mexico, the core of medication was inserted in commercially available punctal plugs. The plugs were placed in 10 eyes of 5 patients with glaucoma, and testing was performed over a 3-month interval. The results showed that the device achieved excellent IOP reduction, a mean of approximately 30%, although retention difficulties occurred in 35% of eyes, Dr. Lewis said. There were no unexpected safety problems such as redness or lash growth, which might have occurred with latanoprost, and one case of canaliculitis.

The main concern in the open-label, uncontrolled pilot study was the suboptimal retention rate, Dr. Lewis said. A randomized, double-masked, parallel group, multicenter phase II study was then performed in the United States, enrolling 61 subjects with bilateral glaucoma. The pressure drop from baseline to week 12 was about 4 to 5.5 mm Hg. The dose delivered via the plug device was equivalent to about 14 eye drops over 12 weeks, significantly less than what would be given in a clinic setting, and this low dose may explain the relatively modest reduction in IOP, Dr. Lewis said. In this trial, investigators used custom plugs in several sizes, which improved the retention rate to over 75%.

Further work is necessary to optimize the concentration of latanoprost for maximum pressure reduction and to enhance retention rates, he continued.