Oxybutynin (OXY) is the most common drug to treat overactive bladder (OAB) syndrome. Transdermal administration is a more ideal route replacing oral administration to resolve problems of low bioavailability and severe side effects. However, commercial transdermal products of OXY frequently cause skin irritation and low permeation efficiency arising discontinued medication. Here, oxybutynin nanosuspension (OXY-NS) and its gel preparation (OXY-NG) were constructed to resolve these issues. In vitro permeation test and in vivo pharmacokinetics study confirmed that OXY-NG significantly enhanced the transdermal permeation of OXY, about 4-fold and 3-fold higher than oxybutynin coarse suspension (OXY-CG), respectively, and in vitro retention test certified that OXY-NG increased OXY concentration especially in viable epidermis (VE) and Dermis (about 3 times that of OXY-CG), consequently improving the bioavailability. Skin irritation assay demonstrated that OXY-NG would not trigger skin adverse effects. In addition, selectively blocking hair follicles test evidenced that hair follicles pathway played an important role in OXY-NS transdermal delivery. In general, by virtue of excellent drug loading, low toxicity and ease of scale-up, OXY-NG is a promising strategy to ameliorate skin permeation of insoluble OXY for better transdermal treatment for OAB, hence increasing its bioavailability, reducing adverse effects, and achieving good patient compliance.
Keywords: Overactive bladder; nanosuspension; nanosuspension gel; oxybutynin; transdermal administration.