Once-daily, extended-release formulations of antimuscarinic agents in the treatment of overactive bladder: a review.

Overactive bladder (OAB) is a chronic condition that often requires long-term treatment to maintain control of symptoms. A range of therapeutic options are available; however, antimuscarinic agents form the mainstay of treatment. Of these agents, tolterodine and oxybutynin are the most widely used. It is well documented that the immediate-release (IR) formulations of these agents have equivalent efficacy in relieving OAB symptoms. However, tolterodine demonstrates a more favorable tolerability profile, particularly in terms of the frequency and severity of dry mouth. Due to the development of novel drug delivery systems, extended-release (ER) formulations of both oxybutynin and tolterodine are now available, permitting once-daily dosing. The convenience of once-daily dosing of antimuscarinic agents would be expected to improve patient compliance and further relieve the symptoms of OAB. Clinical studies with the ER formulations of tolterodine and oxybutynin demonstrate potential clinical advantages over their respective IR forms in terms of either efficacy or tolerability or both, although the therapeutic index of tolterodine ER appears to show a greater advantage over its IR counterpart compared with oxybutynin ER and its IR form. Importantly, the two ER agents have not been compared directly in a head-to-head clinical study. Overall, available clinical data suggest that the newly developed ER formulation of tolterodine represents a significant therapeutic advancement in the treatment of OAB.