Oxybutynin and oxybutynin chloride are used in the treatment of overactive bladder for the relief of symptoms associated with voiding (e.g., urge urinary incontinence, urgency, frequency, urinary leakage, dysuria).
Oxybutynin chloride (as extended-release tablets) also is used for the relief of symptoms of detrusor overactivity associated with a neurologic condition (e.g., spina bifida) in pediatric patients 6 years of age and older.
According to the International Continence Society (ICS), overactive bladder disorder is characterized by involuntary destrusor contractions that may occur spontaneously or may be provoked (by rapid filling, alterations of posture, coughing, walking, jumping). An overactive bladder of neurogenic origin usually has been referred to as an unstable disorder. The hyperflexic overactive bladder disorder usually involves a neurologic disorder.
The diagnosis of neurogenic bladder should be confirmed by cystometry and other appropriate diagnostic procedures before therapy with oxybutynin is initiated. In addition, the patient's response to therapy should be periodically evaluated by cystometry. Appropriate antibacterial therapy should be administered whenever urinary tract infection is present. In limited clinical studies, oxybutynin was more effective than placebo in relieving urinary symptoms associated with neurogenic bladder; however, the drug was not superior to a standard antimuscarinic agent such as propantheline bromide. In one uncontrolled study, oxybutynin was reported to relieve mild to moderate urinary tract discomfort resulting from prostatectomy, radiation therapy, or infection.
Results of one clinical study in patients with overactive bladder indicate that therapy with extended-release oxybutynin chloride tablets (15 mg daily) was substantially more effective than placebo in decreasing the number of urge incontinence episodes. Two randomized, double-blind clinical studies have been conducted to evaluate the comparative efficacy and safety of extended-release oxybutynin tablets and conventional oxybutynin tablets; dosage of both formulations was individualized to balance efficacy and tolerability. When decreases in the number of episodes of urge incontinence were compared, one study indicated that the formulations were comparable; although comparable efficacy was not demonstrated according to predetermined criteria in the second study, there was no substantial difference between the formulations. Efficacy of extended-release oxybutynin tablets was maintained after 12 weeks of therapy in one study.
Therapy with the oxybutynin transdermal system was more effective than placebo in reducing symptoms of overactive bladder. In 2 randomized, double-blind, controlled studies in patients with urge urinary incontinence, treatment with the oxybutynin transdermal system (delivering 3.9 mg of oxybutynin daily) for at least 12 weeks substantially reduced the number of weekly incontinence episodes and increased urinary void volumes compared with placebo. In 1 of the 2 studies, treatment with oxybutynin also substantially reduced the daily micturition frequency compared with placebo.
In one randomized, double-blind, placebo-controlled study of 12 weeks' duration evaluating the comparative efficacy and safety of oxybutynin chloride (5 mg 3 times daily) and tolterodine tartrate (2 mg twice daily) in patients with overactive bladder, efficacy of the 2 drugs appeared to be similar in reducing urinary symptoms of the disorder. Administration of oxybutynin, tolterodine tartrate, or placebo was associated with decreased number of micturitions per 24 hours in 19.5, 21, or 10.5% of patients, respectively, while the mean number of episodes of incontinence decreased by 71, 47, or 19%, respectively. In addition, increases in the volume of urine voided per micturition were similar in patients receiving oxybutynin (mean increase of 31%) and tolterodine (mean increase of 27%) compared with a 7% increase in patients receiving placebo. It appears that tolterodine was better tolerated than oxybutynin; tolterodine was associated with a lower incidence of dry mouth than oxybutinin.
(See Cautions.)Analysis of pooled data from other comparative studies of 12 weeks' duration using the same dosages of oxybutynin and tolterodine tartrate also indicate that efficacy of tolterodine is similar to that of oxybutynin in decreasing the mean number of micturitions per 24 hours and the mean number of episodes of incontinence; although both drugs increased the mean volume voided per micturition, such increases were greater with oxybutynin than with tolterodine. Some clinicians, however, consider tolterodine to be less effective but better tolerated than older agents (e.g., oxybutynin) in the management of overactive bladder.
The efficacy of oral oxybutynin chloride (as conventional tablets, oral solution, or extended-release tablets) for the relief of symptoms of detrusor overactivity associated with a neurologic condition (e.g., spina bifida) in pediatric patients was evaluated in pediatric patients 5-15 years of age in a 24-week, open-label trial. All patients had symptoms of detrusor overactivity in association with a neurologic condition (e.g., spina bifida), used clean intermittent catheterization, and already were users of oxybutynin chloride (at total daily dosages of 10 or 15 mg) at the time of the study. During the study, patients received total daily dosages of oxybutynin chloride ranging from 5-15 mg as conventional tablets, 5-30 mg as oral solution, or 5-20 mg as extended-release tablets. In these patients, oxybutynin chloride therapy was associated with increased mean urine volume per catheterization, increased mean urine volume after morning awakening, and an increase in the mean percentage of catheterizations without a leaking episode. Improvements in bladder function were consistent across all 3 formulations.
Oxybutynin has been used in children for the treatment of primary nocturnal enuresis. In one study in children with a history of nocturnal (but not daytime) enuresis and normal bladders, there was no significant difference in the frequency of nocturnal enuresis when the children were receiving oxybutynin compared to when they were receiving placebo.
Oxybutynin has been used as an antispasmodic in the symptomatic treatment of various GI disorders without conclusive evidence of efficacy.