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BLOG: Sustained drug delivery will benefit the ocular surface
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Delivering drugs slowly to the eye has many benefits, including increased compliance, doctor control of the type of drug used and avoidance of pressure spikes in the case of steroid delivery. The ocular surface, however, may benefit most from a sustained delivery approach.
In my practice, the eye drops we prescribe and the ones patients receive are very often different. Pharmacies, motivated by higher profit margins from generic drugs, often switch our patients to generic “alternatives” that are not always well tolerated on the eye. Preservatives and other inactive ingredients in generic drugs have been shown in a number of studies to deliver variable toxicity to the ocular surface. This is most notable in chronic glaucoma therapy, in which generic prostaglandins and their preservatives cause slow destruction of limbal stem cells. In the shorter-term therapy after cataract surgery, generic ocular surface toxicity can impair visual results for months after the procedure.
It’s amazing to me that with all the drug advances we’ve seen in our careers we still use eye drops to deliver medication to the eye. The pathway between prescribing and the actual delivery of drug is fraught with many pitfalls, and when any eye drop is placed on the eye, it comes at an overwhelmingly high concentration for a very brief time. We can only hope the penetration achieves desired levels. And that’s if the patient takes the drop at all.
Sustained-delivery devices, such as the Ocular Therapeutix punctal depot device and the Icon Bioscience steroid depot, have been used in clinical trials in our practice. For the most part, placing them is a non-event for patients, taking a very brief time, and the patients love that they do not have to use drops. After surgery, in general, the eyes look great, with the same control of inflammation you’d expect with topical therapy but none of the side effects.
With steroids, we want a high initial dose followed by a slow taper. Studies of prednisolone acetate suspension have shown that in many cases, even with vigorous bottle shaking, the amount of actual drug delivered in the first drops is one-eighth the concentration of that delivered toward the end of the bottle. This creates an increasing, rather than decreasing, dose of medication. Pressure spikes and toxicity can naturally result.
With glaucoma medication, slow delivery of a therapeutic dose benefits the eye far more than once- or twice-daily dosing, and clinical trials are beginning to show better diurnal pressure curves with sustained delivery.
As more of these technologies become approved we will have growing options for how we choose to deliver both steroid and glaucoma medications. We will feel more confident that the patient is actually receiving the drug we choose, and the cost to the system will likely decrease rather than increase, as we will see fewer long- and short-term complications that result from patient compliance and ocular surface toxicity.
With better tools we become better doctors, and I am excited to see these technologies become approved in the near future.
Disclosure: Hovanesian reports he is a consultant and clinical investigator for Ocular Therapeutix and Icon Bioscience.