Looking Toward the Future with AzaSite: Results
from 2 Non-clinical Studies
Many of our patients suffer from bacterial conjunctivitis. We
use topical antibiotics to reduce the time of infection, to prevent
re-infection, and to stop the spread of infection to others. There
are a variety of treatment options available, but wouldn't it
be nice to give our patients an opportunity to choose a topical
antibiotic with a convenient dosing regimen and a broad spectrum
of anti-bacterial activity? One of the newest options, AzaSite™
(azithromycin 1% ophthalmic solution), may provide these advantages.
Studies have shown that AzaSite has the ability to penetrate ocular
surfaces (eg, conjunctiva, cornea, eyelids) and target the site
of infection directly, resulting in high tissue concentrations
of azithromycin and a long duration of action.
Pharmacokinetic (PK) studies were conducted in 2007 to evaluate
the distribution of azithromycin in the ocular tissue of pigmented
rabbits after a single-dose comparison of AzaSite and an aqueous
formulation of azithromycin as well as after the multiple-dose
approved regimen of AzaSite (1 drop BID for 2 days, then 1 drop
QD for 5 days). Tissue samples obtained for concentration measures
included: tears, aqueous humor, cornea, conjunctiva, and blood
in both studies; eyelid samples were only obtained in the multiple
dose study. Although both AzaSite and the aqueous formulation
of azithromycin resulted in high exposure of the drug in ocular
tissues, AzaSite was quickly distributed across tissues and demonstrated
a slower clearance rate than the aqueous formulation following
single-dose administration. Increased exposure was observed in
the conjunctiva, cornea, and eyelids, with levels persisting 7
days after the last dose in the multiple-dose administration study.
Cmax values for the ocular tissues were well above those reported
for moxifloxacin, ofloxacin, and gatifloxacin in a rabbit study
published in 2005.
High concentration levels of azithromycin delivered directly
to the key ocular surface tissues and persisting well after the
last dose of the topical antibiotic AzaSite - what does this mean
for our patients? There is an effective, convenient, reduced-dosing
treatment option for bacterial eye infections that actually continues
to the infection site after the therapeutic dosing regimen has
been stopped.
References
1. Data on File. Inspire Pharmaceuticals, Inc., 2007.
2. Inspire Pharmaceuticals, Inc. AzaSite Prescribing Information.
2007.
3. Robertson SM et al. Ocular Pharmacokinetics of Moxifloxacin
after Topical Treatment of Animals and Humans. Survey of Ophthalmology.
Nov 2005; 50(suppl 1):S32-S45.