Drug delivery to the posterior segment of the eye III: the effect of parallel elimination pathway on the vitreous drug level after subconjunctival injection.

The aim of the current study was to study the effect of a parallel elimination pathway on the vitreous drug level after simple injection and application of a zero-order release system by computer simulation. It was found that this pathway gives rise to an early peak time regardless of the physicochemical properties of the applied drug. In addition, the parallel elimination pathway is the major determinant of the vitreous drug level after simple subconjunctival injection. For a zero-order release system, release rate is not the only determinant of pharmacokinetics due to the parallel elimination pathway and k13 also plays a significant role in determining steady-state drug levels. The findings of the current study is necessary for the proper design of a drug delivery system for vitreal drug delivery through subconjunctival injection.