The OROS-based
oxybutynin extended-release (ER) formulation (Lyrinel XL;
Ditropan XL) represents a new form of oral delivery for
oxybutynin, a
muscarinic receptor antagonist used in the treatment of
overactive bladder (OAB). The release of
oxybutynin from
oxybutynin ER occurs in a sustained manner, resulting in a smoother plasma concentration-time profile and a lower maximum plasma concentration than those seen with
oxybutynin immediate-release (IR). The ER formulation has been developed with the aim of improving the tolerability of
oxybutynin therapy and facilitating once-daily administration. Moreover,
oxybutynin ER offers greater flexibility in dosage (5-30 mg/day) than the other available treatment options. At dosages of 5-30 mg once daily,
oxybutynin ER produced significant decreases from baseline in weekly
urinary urge incontinence in patients with OAB. In addition, there were significant decreases in weekly total incontinence episodes and micturition frequency. In two randomised, double-blind studies in patients with OAB, the improvement in all the symptoms with once-daily
oxybutynin ER 5-30 mg/day was similar to that produced by
oxybutynin IR 5-20 mg/day given one to four times daily. Once-daily
oxybutynin ER 10 mg was superior to
tolterodine IR 4 mg/day given as two daily doses and as effective as once-daily
tolterodine ER 4 mg/day in decreasing
urinary incontinence; the decreases in micturition frequency with
oxybutynin ER were significantly greater than those seen with either of
tolterodine formulations.
Oxybutynin ER was well tolerated in all the trials, with adverse events usually being mild to moderate and transient. In direct comparisons, the overall tolerability profile of
oxybutynin ER was better than that of
oxybutynin IR.
Oxybutynin ER was similar to
tolterodine (IR and ER) with respect to the incidence of clinically important dry mouth. A large 12-month tolerability study demonstrated no significant risks associated with the long-term use of
oxybutynin ER. A few noncomparative studies have shown promising results with
oxybutynin ER in the treatment of adult and paediatric patients with
neurogenic bladder dysfunction secondary to neuronal injury. Long- and short-term studies have reported significant improvements in health-related quality of life with
oxybutynin ER
therapy. In addition, pharmacoeconomic studies have suggested that
oxybutynin ER is more cost effective than
oxybutynin IR and at least as cost effective as
tolterodine IR. In conclusion,
oxybutynin ER shows excellent efficacy in the treatment of symptoms associated with OAB in adults and the elderly with a good tolerability profile over a prolonged period of use (12 months). The ER formulation of
oxybutynin provides a smooth plasma concentration profile over the 24-hour dosage interval, facilitating once-daily administration. Hence, given its overall efficacy/tolerability profile and dosage flexibility,
oxybutynin ER provides an excellent treatment option in the first-line
pharmacotherapy of OAB.