Sustained-release medications on the way

San Francisco-A new generation of drug delivery devices promises to make eye drops the drug delivery vehicle of the past.

“We all know the problems with persistence and lack of adherence,” said Ike Ahmed, MD, assistant professor at the University of Toronto. “We would all like to see better treatments, extended-release treatments that get us around persistence and adherence issues. And they are on the way.”

Multiple new drug delivery devices are in development and in testing that offer some version of extended-release or sustained-release dosing of familiar ocular drugs. Several companies have already marketed devices in Europe, though few have yet been cleared for marketing in the United States.

Ophthalmologists can expect a surge in demand as these devices are approved, Dr. Ahmed said. A recent study in Singapore found that patients with glaucoma not only preferred sustained-delivery devices to the familiar eye drops, they were willing to pay higher out-of-pocket costs for sustained delivery compared with drops.

“The clinical idea is to deliver the drug to the site of action,” he said. “For patients, the idea is to lose the bother and the mess and the pain of drops. And with sustained release, they don’t have to put up with common complications like red eye.”

Sustained-release devices are driven largely by ocular anatomy, he explained. Depending on the drug and the device design, therapy can be delivered directly and exclusively to almost any ocular tissue: intravitreal, suprachoroidal, subconjunctival, scleral, and more.

The range of devices grows almost by the month.

Drug-eluting contact lens devices deliver drug for 2 to 4 weeks. Some are designed to be work 24/7, others are to be worn for a few hours daily.

Drug-eluting punctal plugs are designed to deliver steady state drug dosing for 30 days and longer.

Topical elastomers are designed to float on the eye, usually beneath the eyelid, and can function as drug depots, drug-eluting devices, or both. Some elastomers deliver a single drug and others can deliver multiple drugs at different rates.

Other companies are developing injectable drug depots that are bioabsorbable over a controlled period. Some depots are made of viscous collagen; others are liquids that form visible spheres within the aqueous humor.

Most of the injected or implanted devices can be removed easily, sometimes by simple needle aspiration. At least one subconjunctival pump is being developed that can be refilled by injection to allow use for several years.

“In our current regulatory environment, we are probably 4 to 5 years away from approval for many of these devices,” Dr. Ahmed said. “But sustained release is clearly moving toward clinical use.”

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