Formulation study of intravesical oxybutynin instillation solution with enhanced retention in bladder.

A formulation study of intravesical oxybutynin (OB) preparations was carried out in order to improve the effectiveness in intravesical instillation therapy for spastic neurogenetic bladder. Sodium hyaluronate (HYA) was introduced to enhance the muco-adhesiveness of the instillation preparation, and the physicochemical properties of the OB formulation were evaluated in comparison with a conventional formulation containing hydroxypropylcellulose (HPC). The viscous properties and in vitro adhesiveness increased with the amount of the polymeric additives, and retention properties of OB in rabbit bladder were comparable after addition of 0.4% HYA and 1.0% HPC. HYA was able to enhance the intravesical retention properties of OB instillation solution to a lesser degree than HPC, it seemed to be a useful additive in the OB instillation due to its safety and mucosal-protective effect.