The validity of rabbits for investigations on ophthalmic vehicles: a comparison of four different vehicles containing tropicamide in humans and rabbits

Saettone, M.F.; Giannaccini, B.; Barattini, F.; Tellini, N.

Pharmaceutica Acta Helvetiae 57(2): 47-55

1982


ISSN/ISBN: 0031-6865
PMID: 7071067
Document Number: 5910
The mydriatic effect of tropicamide in four different vehicles, at concentrations ranging from 0.0025 to 0.2% wlv, was investigated in rabbits. The vehicles were 1. a buffered isotonic solution (AS); 2. a viscous solution containing hydroxypropylcellulose (VS); 3. a suspension -type paraffin ointment (OV); and 4. an aqueous gel (AG). The study was aimed at establishing correlations between rabbit data, and human data obtained with the same vehicles in a previous study. It was thus hoped to gain information on the validity of rabbits as experimental animals for investigations on ophthalmic vehicles. Rabbits proved to be much less sensitive than humans to moderate increases of the viscosity of the vehicle. The bioavailability of tropicamide from the ointment was also significantly lower than in humans, probably on account of the absence, in the rabbit's eye, of shear phenomena facilitating release. The aqueous gel was found to promote to a significant degree the bioavailability of tropicamide in rabbits, although the effect in humans was comparatively more pronounced. The results are discussed, and related to the different biologic parameters and structures, influencing transcorneal absorption in the two species.

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The validity of rabbits for investigations on ophthalmic vehicles: a comparison of four different vehicles containing tropicamide in humans and rabbits