Oxybutynin topical and transdermal formulations: an update

Oxybutynin, an antimuscarinic agent, is well established for the treatment of overactive bladder (OAB) and is the gold standard for the treatment of severe neurogenic bladder. Although oral oxybutynin is effective in relieving the urinary symptoms of OAB, medication adherence is low at least in part because of substantial anticholinergic adverse effects. The poor anticholinergic tolerability has been attributed to high circulating levels of N-desethyloxybutynin (DEO), a pharmacologically active product of presystemic metabolism of oral oxybutynin in the liver and gastrointestinal tract. Transdermal formulations of oxybutynin avoid first-pass metabolism and thereby produce lower DEO plasma concentrations. Oxybutynin chloride topical gel (OTG) (Gelnique(R), Watson Pharmaceuticals, Corona, CA, USA), a new gel-based transdermal formulation of oxybutynin, was approved by the U.S. Food and Drug Administration in January 2009. Results of a placebo-controlled U.S. phase III study demonstrated that OTG is efficacious in relieving symptoms of OAB and is associated with a low incidence of anticholinergic adverse events. Patients may find that OTG, with its excellent efficacy, convenient once-daily application and outstanding tolerability profile, is a valuable alternative to oral antimuscarinic agents for the treatment of OAB.