Oxybutynin Extended Release and Tolterodine Immediate Release
Oxybutynin Extended Release and Tolterodine Immediate Release
Objective: To evaluate the cost-effectiveness of a new extended-release (XL) formulation of oxybutynin relative to tolterodine immediate release (IR), currently the most prescribed treatment for overactive bladder in the UK.
Methods: A state-transition model was developed to compare outcomes over 1 year. Effectiveness and treatment persistence data were derived from the OBJECT (Overactive Bladder: Judging Effective Control and Treatment) study, a 3-month clinical trial comparing oxybutynin XL 10 mg/day with tolterodine IR 4 mg/day. The daily costs of oxybutynin XL and tolterodine IR were £0.82 and £1.04, respectively. These data and information from the literature were used to project outcomes beyond the trial time. Severity-specific incontinence cost profiles were developed for the UK (2002 costings).
Results: After 1 year, 3.1 more patients per 100 treated attained complete continence with oxybutynin XL compared with tolterodine IR, and 5.6% more had less than seven incontinent episodes per week. Over 1 year, patients receiving oxybutynin XL had almost 17 additional incontinence-free days and 95 fewer incontinent episodes. Estimated costs were £86 lower per patient with oxybutynin XL. If drugs are priced equally, savings decrease to £21 per patient. Oxybutynin XL maintains its advantage over wide ranges of inputs, and outcomes are similar if analyses are limited to 3 months.
Conclusion: Base-case analyses suggest that oxybutynin XL provides better effectiveness than tolterodine IR and reduces costs. Results indicate that oxybutynin XL is the dominant therapeutic option under a wide range of alternative inputs and assumptions.
Overactive bladder is a prevalent and distressing condition resulting in symptoms of urinary frequency (more than eight micturitions per 24 hours) and urge or reflex incontinence that occurs singly or in any combination. This chronic condition is defined urodynamically as detrusor overactivity, and characterised by involuntary bladder contractions during the filling phase of the micturition cycle, resulting in decreased bladder capacity.
Based on a survey of 16 776 adults >40 years of age, it has been estimated that the prevalence of overactive bladder in six European countries ranges from 12% (Italy and France) to 22% (Spain). This same survey also reported a higher prevalence with increasing age and in women compared with men. In a more recent study, the prevalence of incontinence among adults in the UK was reported to be 11% for women and 5% for men.
The impact of this condition on quality of life can be substantial. Unfortunately, incontinence also seems to be undertreated. A recent survey among community-dwelling seniors in the UK reported that only 4045% of incontinent seniors used health services for their condition.
While studies of the cost of overactive bladder are few, it has been estimated that in 1998 incontinence cost the National Health Service (NHS) in England £353 595 000. In the US, the cost of incontinence was reported to reach $US3565 per affected person or $US26 billion in total. Clearly, the economic impact of this condition is significant.
The most common conservative treatment for overactive bladder is drug therapy. Most patients with this condition have been prescribed antimuscarinic agents, such as immediate-release (IR) oxybutynin, because it is widely believed that bladder contraction is mediated by the stimulation of muscarinic receptors. Oxybutynin extended release (XL) is a new formulation that provides constant delivery of the drug over a 24-hour period. This formulation has been designed to release the drug primarily in the lower gastrointestinal tract to minimise first-pass metabolism and, consequently, to reduce adverse events. IR oxybutynin is released in the upper gastrointestinal tract where it is rapidly metabolised by the cytochrome p450 system to desethyloxybutynin, which may be responsible for its poor tolerability in some patients.
While IR oxybutynin is currently the treatment of choice for overactive bladder, tolterodine IR is also available to patients in whom IR oxybutynin is ineffective or not well tolerated. In OBJECT (Overactive Bladder: Judging Effective Control and Treatment), a recent clinical trial of oxybutynin XL versus tolterodine IR, oxybutynin XL was significantly more effective at reducing urge incontinence episodes, total incontinence episodes, and micturition frequency while demonstrating an equivalent tolerability profile. These results suggest that oxybutynin XL would be a welcome addition to the pharmacological treatments available to patients with overactive bladder who cannot tolerate conventional treatment.
Given these results of the OBJECT study, a pharmacoeconomic model was developed comparing the two treatments, oxybutynin XL and tolterodine IR, using actual drug costs. Outcomes are estimated for a UK population of community-dwelling adults with urge or mixed urinary incontinence.
Objective: To evaluate the cost-effectiveness of a new extended-release (XL) formulation of oxybutynin relative to tolterodine immediate release (IR), currently the most prescribed treatment for overactive bladder in the UK.
Methods: A state-transition model was developed to compare outcomes over 1 year. Effectiveness and treatment persistence data were derived from the OBJECT (Overactive Bladder: Judging Effective Control and Treatment) study, a 3-month clinical trial comparing oxybutynin XL 10 mg/day with tolterodine IR 4 mg/day. The daily costs of oxybutynin XL and tolterodine IR were £0.82 and £1.04, respectively. These data and information from the literature were used to project outcomes beyond the trial time. Severity-specific incontinence cost profiles were developed for the UK (2002 costings).
Results: After 1 year, 3.1 more patients per 100 treated attained complete continence with oxybutynin XL compared with tolterodine IR, and 5.6% more had less than seven incontinent episodes per week. Over 1 year, patients receiving oxybutynin XL had almost 17 additional incontinence-free days and 95 fewer incontinent episodes. Estimated costs were £86 lower per patient with oxybutynin XL. If drugs are priced equally, savings decrease to £21 per patient. Oxybutynin XL maintains its advantage over wide ranges of inputs, and outcomes are similar if analyses are limited to 3 months.
Conclusion: Base-case analyses suggest that oxybutynin XL provides better effectiveness than tolterodine IR and reduces costs. Results indicate that oxybutynin XL is the dominant therapeutic option under a wide range of alternative inputs and assumptions.
Overactive bladder is a prevalent and distressing condition resulting in symptoms of urinary frequency (more than eight micturitions per 24 hours) and urge or reflex incontinence that occurs singly or in any combination. This chronic condition is defined urodynamically as detrusor overactivity, and characterised by involuntary bladder contractions during the filling phase of the micturition cycle, resulting in decreased bladder capacity.
Based on a survey of 16 776 adults >40 years of age, it has been estimated that the prevalence of overactive bladder in six European countries ranges from 12% (Italy and France) to 22% (Spain). This same survey also reported a higher prevalence with increasing age and in women compared with men. In a more recent study, the prevalence of incontinence among adults in the UK was reported to be 11% for women and 5% for men.
The impact of this condition on quality of life can be substantial. Unfortunately, incontinence also seems to be undertreated. A recent survey among community-dwelling seniors in the UK reported that only 4045% of incontinent seniors used health services for their condition.
While studies of the cost of overactive bladder are few, it has been estimated that in 1998 incontinence cost the National Health Service (NHS) in England £353 595 000. In the US, the cost of incontinence was reported to reach $US3565 per affected person or $US26 billion in total. Clearly, the economic impact of this condition is significant.
The most common conservative treatment for overactive bladder is drug therapy. Most patients with this condition have been prescribed antimuscarinic agents, such as immediate-release (IR) oxybutynin, because it is widely believed that bladder contraction is mediated by the stimulation of muscarinic receptors. Oxybutynin extended release (XL) is a new formulation that provides constant delivery of the drug over a 24-hour period. This formulation has been designed to release the drug primarily in the lower gastrointestinal tract to minimise first-pass metabolism and, consequently, to reduce adverse events. IR oxybutynin is released in the upper gastrointestinal tract where it is rapidly metabolised by the cytochrome p450 system to desethyloxybutynin, which may be responsible for its poor tolerability in some patients.
While IR oxybutynin is currently the treatment of choice for overactive bladder, tolterodine IR is also available to patients in whom IR oxybutynin is ineffective or not well tolerated. In OBJECT (Overactive Bladder: Judging Effective Control and Treatment), a recent clinical trial of oxybutynin XL versus tolterodine IR, oxybutynin XL was significantly more effective at reducing urge incontinence episodes, total incontinence episodes, and micturition frequency while demonstrating an equivalent tolerability profile. These results suggest that oxybutynin XL would be a welcome addition to the pharmacological treatments available to patients with overactive bladder who cannot tolerate conventional treatment.
Given these results of the OBJECT study, a pharmacoeconomic model was developed comparing the two treatments, oxybutynin XL and tolterodine IR, using actual drug costs. Outcomes are estimated for a UK population of community-dwelling adults with urge or mixed urinary incontinence.
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