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November 1,
1997
SAN JOSE - An intraocular
drug delivery system (DDS) containing dexamethasone may be an effective,
efficient and patient-friendly way to suppress inflammation following
cataract surgery. The system is designed to gradually release dexamethasone
directly into the anterior segment.
Therapeutic efficacy
may be improved by eliminating the problems of compliance and corneal
penetration, according to David F. Chang, MD, a cataract surgeon in private
practice in Los Altos, Calif., and associate clinical professor of ophthalmology
at the University of California, San Francisco. Dr. Chang was one of four
clinical investigators for the Food and Drug Administration phase 2 clinical
trials of the device which recently have been completed.
He said traditional
perioperative drug delivery methods - eye drops, subconjunctival injection,
collagen shields and placement in the infusion bottle - all fail to maintain
a high level of drug within the eye for a long enough period of time.
Drawbacks to using postop eye drops, he continued, include the need for
patient education and compliance.
"The ideal perioperative
drug delivery system would achieve a high and sustained intraocular drug
level, would be compatible with topical anesthesia and immediate vision
and would eliminate patient involvement by making postop drops unnecessary,"
Dr. Chang said.
The dexamethasone
DDS was developed by Oculex Pharmaceuticals, Inc., of Sunnyvale, Calif.,
and is to be marketed by Storz Ophthalmics, of St. Louis. The implant
consists of a tiny, free-floating biodegradable polymer, which is delivered
into the anterior chamber (AC) with forceps at the end of surgery. "Oculex
is able to bind a variety of drugs to biodegradable polymers that can
be formulated to dissolve and release the drug over a programmed period
of time. This delivery period can range from several days up to a year,"
Dr. Chang said.
Therapeutic advantages
As formulated currently
for cataract surgery, Surodex contains 60 µg of dexamethasone, which is
gradually released within the anterior segment over a 1-week period. This
is approximately the same amount of dexamethasone as a single drop of
Decadron (Merck & Co.).
"Conventional q.i.d.
topical regimens deliver about a 250 µg daily dose of dexamethasone topically,"
Dr. Chang said. "However, rabbit studies have shown that by bypassing
the cornea, the 60 µg intraocular delivery system can achieve higher continuous
levels of dexamethasone within the eye than is possible with eye drops
alone. "
In the FDA phase 1
clinical trial, six patients were followed for 3 months following insertion
of dexamethasone DDS after cataract surgery. No complications or side
effects were observed. Five of the six patients had no cell or flare at
1 week postop, and the sixth was clinically quiet by the second week.
"A separate randomized double blind study from Singapore showed the product
to be clinically superior to dexamethasone drops at suppressing post-cataract
inflammation, as judged by AC flare," he said. [see "Sustained release
drug system may be more effective than topical," Ocular Surgery News,
June 1, 1997]
Patient and physician advantages
"It was fairly easy
to recruit patients for the phase 2 study because of the potential that
they wouldn't have to use drops," Dr. Chang said. "We often underestimate
how difficult this responsibility is for some patients, most of whom consider
taking drops to be more difficult than pills."
"With an intraocular
delivery system, we may be able to avoid all of the problems of patient
compliance with eye drops," he said. "Patients must fill and refill their
prescriptions, keep their bottles sterile, remember which medication to
use when, adequately shake suspensions and get each drop into the cul-de-sac
with enough contact time to penetrate the cornea. Some patients require
another person to assist them.
"Meanwhile, we and
our staffs spend significant time postop on prescriptions and patient
questions and education regarding medications. Indeed, one function of
postop visits is to assess anti-inflammatory drug compliance and response.
"This is a win-win
concept. If this drug delivery method proves to be therapeutically superior
and minimizes the need for patient drug compliance and education, it will
be a system that is more patient-friendly, more physician-friendly and
more cost effective to the health care delivery system," he said.
For
Your Information:
- David F. Chang,
MD, associate clinical professor of ophthalmology at the University
of California, San Francisco, can be reached at his private practice
specializing in cataract surgery, 762 Altos Oaks Dr., Ste. 1, Los
Altos, CA 94024. Dr. Chang has no direct financial interest in the
products mentioned in this article, nor is he a paid consultant for
any companies mentioned.
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