Polymethacrylate microparticles gel for topical drug delivery.

Evaluating the potentials of particulate delivery systems in topical drug delivery. Polymethacrylate microparticles (MPs) incorporating verapamil hydrochloride (VRP) as a model hydrophilic drug with potential topical clinical uses, using Eudragit RS100 and Eudragit L100 were prepared for the formulation of a composite topical gel. The effect of initial drug loading, polymer composition, particularly the proportion of Eudragit L100 as an interacting polymer component and the HLB of the dispersing agent on MPs characteristics was investigated. A test MPs formulation was incorporated in gel and evaluated for drug release and human skin permeation. MPs showed high % incorporation efficiency and % yield. Composition of the hybrid polymer matrix was a main determinant of MPs characteristics, particularly drug release. Factors known to influence drug release such as MPs size and high drug solubility were outweighed by strong VRP-Eudragit L100 interaction. The developed MPs gel showed controlled VRP release and reduced skin retention compared to a free drug gel. Topical drug delivery and skin retention could be modulated using particulate delivery systems. From a practical standpoint, the VRP gel developed may offer advantage in a range of dermatological conditions, in response to the growing off-label topical use of VRP.