S. Muchtar et al., EX-VIVO PERMEATION STUDY OF INDOMETHACIN FROM A SUBMICRON EMULSION THROUGH ALBINO RABBIT CORNEA, Journal of controlled release, 44(1), 1997, pp. 55-64
Indomethacin was incorporated in an original emulsion formulation stab
ilized by a combination of phospholipids and an amphoteric surfactant,
lauroamphodiacetate. The solubility of indomethacin in the various em
ulsion phases was pH-dependent. The pH of the emulsion was adjusted to
3.8 in order to promote localization of the drug in the oil phase and
prevent drug ionization. Ionization would increase drug aqueous solub
ility and result in indomethacin precipitation. Optimal manufacturing
conditions were identified yielding an emulsion with a mean droplet si
ze of 110 +/- 20 nm and a zeta potential value of -50 mV. The emulsion
was found to be chemically and physically stable for more than 5 mont
hs at 4 degrees C. The results of the ocular tolerance study in rabbit
eye indicated that hourly administration of the emulsion vehicle was
well tolerated without any toxic or inflammatory response to the ocula
r surface during the 5 days of the study. Scanning electron microscopy
revealed a normal corneal surface resembling that of the animals trea
ted with physiological saline. The penetration rate of indomethacin th
rough excised rabbit eye cornea from the emulsion and from a marketed
product (Indocollyre(R)) were determined and compared using a novel mo
unted corneal diffusion assembly. It was shown that the apparent corne
al permeability coefficient of indomethacin incorporated in the emulsi
on was 3.8 times greater than that of indomethacin in the marketed aqu
eous solution. The increase in corneal drug permeation could be attrib
uted to various causes that are discussed in the manuscript.