Biodegradable intrascleral implant for sustained intraocular delivery of betamethasone phosphate.
OBJECTIVE
To evaluate the feasibility of using a biodegradable intrascleral implant for intraocular sustained delivery of betamethasone phosphate (BP).


METHODS
The intrascleral implant (0.5 mm thick and 4 mm in diameter) was made of poly(DL-lactide) containing 25% betamethasone phosphate. The in vitro release of BP from the implant was evaluated by high-performance liquid chromatography (HPLC). The implants were placed into a scleral pocket in the rabbit's eye. The concentrations of BP in the aqueous humor, vitreous, and retina-choroid were measured by HPLC. The toxicity and biocompatibility of the implant were evaluated by slit lamp examination, electroretinography, and light microscopy.


RESULTS
In vitro studies demonstrated that the implants released BP in a biphasic pattern for at least 8 weeks. The BP concentrations in the vitreous and the retina-choroid remained within the concentration range capable of suppressing inflammatory responses for more than 8 weeks. The BP concentration was greater in the retina-choroid than in the vitreous. In the aqueous humor, BP was below the detection limit during the observation period. No significant toxicity to the retina was observed. Also, the implant showed good biocompatibility in the eye.


CONCLUSIONS
These results suggest that the intrascleral implant would be a promising system for delivery of steroid to the posterior segment of the eye.
Okabe
Junko
J
Department of Ophthalmology, Nagoya City University Medical School, Nagoya, Japan.
Kimura
Hideya
H
Kunou
Noriyuki
N
Okabe
Komei
K
Kato
Aki
A
Ogura
Yuichiro
Y
D020341:Absorbable Implants; D000818:Animals; D001082:Aqueous Humor / Q000378:metabolism; D001623:Betamethasone / Q000008:administration & dosage* / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D002829:Choroid / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D003692:Delayed-Action Preparations; D016503:Drug Delivery Systems; D004343:Drug Implants; D004596:Electroretinography; D005240:Feasibility Studies; D005938:Glucocorticoids / Q000008:administration & dosage* / Q000493:pharmacokinetics; D011091:Polyesters; D011817:Rabbits; D012160:Retina / Q000378:metabolism; D012590:Sclera / Q000187:drug effects*; D014822:Vitreous Body / Q000378:metabolism
D003692:Delayed-Action Preparations; D004343:Drug Implants; D005938:Glucocorticoids; D011091:Polyesters; C033616:poly(lactide); C028994:betamethasone sodium phosphate; D001623:Betamethasone