Quantitation of pilocarpine delivery across isolated rabbit cornea by noncross-linked high viscosity polymer gel

The effect on pilocarpine flux across rabbit cornea in vitro by a noncross-linked polymeric gel vehicle was measured. A closed system transport chamber was used. Its design featured continuous flow of a tear analog but excluded variables of the internal eye. Results were compared to previously determined data in the same chamber system for cross-linked hydrogel buttons and for free pilocarpine fluid. Gel-mediated flux was equal to that with lens buttons to 90 minutes in the case of a 30 per cent gel (viscosity approximately 70,000 centipoises). Elution by the tear analog system limited flux duration of gels relative to lenses. Greater viscosity of 30 per cent gel relative to 25 per cent gel (approximately 15,000 centipoises) was associated with prolonged transcorneal drug flux. The congruence of flux slopes for 30 per cent gel and lens button vehicles despite the difference in available dose suggests saturable mediation of pilocarpine transport across the cornea, but a greater "flux efficiency" through 90 minutes for 30 per cent gel.