The pharmacokinetics of intravesical and oral oxybutynin chloride

Treating Lower Urinary Tract Symptoms in Older Adults: Intravesical Options

This article provides an overview of the diagnosis and the treatment of lower urinary tract symptoms in older adults complicated by the neurodegenerative changes in the micturition reflex and further confounded by age-related decline in hepatic and renal clearance raising the propensity of adverse drug reactions. The first-line drug treatment for lower urinary tract symptoms, orally administered antimuscarinics, fails to reach the equilibrium dissociation constant of muscarinic receptors even at their maximum plasma concentration and tends to evoke a half-maximal response at a muscarinic receptor occupancy of just 0.206% in the bladder with a minimal difference from exocrine glands, which raises the adverse drug reaction risk. On the contrary, intravesical antimuscarinics are instilled at concentrations 1000-fold higher than the oral maximum plasma concentration and the equilibrium dissociation constant erects a downhill concentration gradient that drives passive diffusion and achieves a mucosal concentration around ten-fold lower than the instilled concentration for a long-lasting occupation of muscarinic receptors in mucosa and sensory nerves. A high local concentration of antimuscarinics in the bladder triggers alternative mechanisms of action and is supposed to engage retrograde transport to nerve cell bodies for neuroplastic changes that underlie a long-lasting therapeutic effect, while an intrinsically lower systemic uptake of the intravesical route lowers the muscarinic receptor occupancy of exocrine glands to lower the adverse drug reaction relative to the oral route. Thus, the traditional pharmacokinetics and pharmacodynamics of oral treatment are upended by intravesical antimuscarinics to generate a dramatic improvement (~ 76%) noted in a meta-analysis of studies enrolling children with neurogenic lower urinary tract symptoms on the primary endpoint of maximum cystometric bladder capacity as well as the secondary endpoints of filling compliance and uninhibited detrusor contractions. The therapeutic success of intravesical multidose oxybutynin solution or oxybutynin entrapped in the polymer for sustained release in the pediatric population bodes well for patients with lower urinary tract symptoms at the other extreme of the age spectrum. Though generally used to predict oral drug absorption, Lipinski's rule of five can also explain the ten-fold lower systemic uptake from the bladder of positively charged trospium over oxybutynin, a tertiary amine. Chemodenervation by an intradetrusor injection of onabotulinumtoxinA is merited for patients with idiopathic overactive bladder discontinuing oral treatment because of a lack of efficacy. However, age-related peripheral neurodegeneration potentiates the adverse drug reaction risk of urinary retention that motivates the quest of liquid instillation, delivering larger fraction of onabotulinumtoxinA to the mucosa as opposed to muscle by an intradetrusor injection can also probe the neurogenic and myogenic predominance of idiopathic overactive bladder. Overall, the treatment paradigm of lower urinary tract symptoms in older adults should be tailored to individual's overall health status and the risk tolerance for adverse drug reactions.

Dosing Variability and Clinical Outcomes of Oxybutynin: A Pediatric Cohort of Patients With Neurogenic Bladder

Background

Despite the therapeutic advancements of the last several decades, neurogenic bladder remains a significant source of morbidity for patients with a spinal pathology. Oxybutynin is a mainstay of treatment in pediatric populations despite significant side effects and highly variable bioavailability.

Objectives

To characterize the use of oxybutynin in a cohort of pediatric patients with neurogenic bladder.

Methods

Retrospective data were collected of dosing, drug interactions, and urodynamics parameters in the 100 consecutive patients in a spinal differences clinic who had an appointment between October 7, 2015, and December 30, 2015. In addition to descriptive statistics, a linear regression model of oxybutynin dose versus age and sex was developed to examine the impact of age on dosing variability.

Results

One hundred patients (52% female) with a median age of 6.8 years were included. The median daily dose of oxybutynin was 0.36 mg/kg (interquartile range, 0.28-0.54 mg/kg). Of the 48 patients with a recent urodynamics study, 13 had a detrusor leak point pressure (DLPP) greater than the typical cutoff of 40 cm H₂O, indicating a need for management escalation. However, of these 13 patients, 38% were already on or exceeding oxybutynin's maximum recommended dose.

Conclusion

The wide dosing variability and high DLPPs despite maximal dosing indicate a need for further investigation of oxybutynin's bioavailability in this population compared to its side effects and clinical outcomes. If variability in response to the medication is due to differences in bioavailability, then a precision-dosing model based on patient genomics could be developed for oxybutynin.

Intravesical sustained release system of lidocaine and oxybutynin results from in vitro and animal study

PURPOSE

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a chronic debilitating condition of unknown etiology. Intravesical lidocaine demonstrated pain relief in patients with IC/BPS. Intravesical oxybutynin has shown therapeutic efficacy in patients with urinary bladder disorders. However, loss of drug with urination requiring multiple administrations and immediate dilution of drug concentration by residual urine in the bladder mitigated intravesical use of both drugs in clinical practice. The aim of this study was to evaluate the efficacy and safety of fixed-dose combination of lidocaine and oxybutynin, forming in the urine a sustained delivery system named TRG-042.

MATERIAL AND METHODS

In-vitro, we have quantitatively tested the concentration of lidocaine and oxybutynin released from TRG-042 in artificial urine. Following the successful in-vitro study weekly formulation of TRG-042 was instilled intravesically to six pigs. All pigs were followed with cystoscopy to assess the gradual degradation of the delivery system and to evaluate bladder response over 7 days. Daily blood samples were tested for drug quantization.

RESULTS

In-vitro studies have demonstrated oxybutynin and lidocaine sustained release over 1-week period coupled with full degradation of the matrix. None of the animals demonstrated any side effects following instillation. Cystoscopy examination observed gradual disintegration of TRG-042 over 1-week with no adverse reaction to the mucosa. Plasma concentrations of oxybutynin and lidocaine were uniformly stable over the 1-week period [1.46 ± 0.176 ng/ml and 4.29 ± 2.48 ng/ml respectively(mean ± SEM)] with almost undetectable concentration of N-desethyloxybutynin (NDO)[0.032 ± 0.068 ng/ml].

CONCLUSIONS

The in-vitro and animal data demonstrated that TRG-042 can safely be used for intravesical sustained release of lidocaine and oxybutynin in the treatment of BPS/IC.

Comprehensive overview of the available pharmacotherapy for the treatment of non-neurogenic overactive bladder in children

INTRODUCTION

Overactive bladder (OAB) is a chronic condition highly prevalent in children and causing bothersome symptoms. It is often associated with deterioration of quality of life and can be devastating for patients and their families. Prompt initiation of conservative measures should be the backbone of treatment. When conservative management fails, pharmacological options must be considered.

AREAS COVERED

Although antimuscarinics are considered the mainstay of pharmacological treatment for OAB, only two agents are currently approved for the pediatric population. Oxybutynin and propiverine are discussed in this review, as well as other non-approved antimuscarinic agents and β3-agonists with related literature to substantiate their use in children. Dual therapy along with medication adherence and persistence is also discussed.

EXPERT OPINION

The treatment of OAB in children is demanding and one must rely on a structured, stepwise approach to achieve success. Discussing conservative measures and prescribing medication is not enough. Clinicians should actively involve children and their families in the treatment, set realistic expectations, and closely monitor side effects and medication adherence to ensure maximal efficacy.

A Population Pharmacokinetic Model of (R)- and (S-) Oxybutynin and Its Active Metabolites After Oral and Intravesical Administration to Healthy Volunteers

Oxybutynin is a racemic anticholinergic drug used for the symptomatic treatment of detrusor overactivity. The formation of active metabolites related to tolerability problems depends on the route of administration. The objective of this evaluation was to develop a pharmacokinetic model for oral/intravesical administration as the basis for simulations with different dosages. Data from a published changeover clinical study with 18 healthy adults receiving a single oral dose of 5 mg immediate-release oxybutynin and single and multiple intravesical doses of 10 mg oxybutynin solution was evaluated. Enantioselective plasma concentrations of oxybutynin and N-desethyloxybutynin (NDO) were used to establish a population pharmacokinetic model using nonlinear mixed-effects modeling with NONMEM 7.4.1. For both enantiomers, the data were described well by a 2-compartment model for oxybutynin with an additional compartment for NDO. Oxybutynin absorption was modeled by transit compartments for oral and first-order absorption for intravesical application. Bioavailability of the more active (R)-enantiomer was 7% for oral and 10%-22% for intravesical administration. In simulations, intravesical doses of 5 to 15 mg (R)-oxybutynin administered 2 to 3 times daily decreased peak-trough fluctuations of NDO to 8% compared with 24% after oral administration. The NDO/oxybutynin ratio was reduced from 17 after oral administration to unity. Chronic intravesical versus oral administration of (R)-oxybutynin generates distinctly lower and less variable concentrations of (R)-NDO. Pharmacokinetic simulations suggest that exposure for 12.5 mg (R)-oxybutynin administered twice daily might not compromise efficacy and tolerability compared with exposure for standard thrice-daily administrations. This assumption needs to be assessed in clinical studies.

A randomized, crossover trial comparing the efficacy and safety of fesoterodine and extended-release oxybutynin in children with overactive bladder with 12-month extension on fesoterodine: The FOXY study

INTRODUCTION

We sought to assess and compare safety and efficacy of fesoterodine and oxybutynin extended-release in the treatment of pediatric overactive bladder (OAB).

METHODS

We conducted a non-inferiority, randomized, double-blind, crossover trial comparing fesoterodine 4-8 mg and oxybutynin 10-20 mg once daily (QD) in children with OAB aged 5-14 years (2015-2018). Every child received the first medication for eight weeks, followed by crossover to the second antimuscarinic after a three-days washout. Dose up-titration was possible at mid-course. Patients could enter a fesoterodine 12-month extension. Endpoints were assessed through changes on voiding diaries, Patient's Perception of Bladder Condition score (PPBC), adverse events, vital signs, electrocardiogram, post-void residual, urinalysis, and blood tests. The Wilcoxon rank sum and Wilcoxon signed rank tests were used for statistical analysis.

RESULTS

A total of 62 patients were randomized (two early dropouts). Expected class effects (dry mouth/constipation) were present but no significant difference was observed. There was a 10.1 beats/minute increase in heart rate with fesoterodine (p<0.01) (oxybutynin-1.9 beats/min; p=non-significant [ns]). No life-threatening or serious adverse events occurred. Efficacy was similar for both drugs. Bladder capacity improved over the 16 months of the study; baseline capacity of 125 mL (44.5% expected bladder capacity for age [%EBC]) to 171 mL (53.9 %EBC) at the end of the extension phase. No clinical or statistical difference was shown between efficacy measures for fesoterodine or oxybutynin.

CONCLUSIONS

The use of fesoterodine or oxybutynin appear safe and effective for the treatment of OAB in children. Based on our study, long-term treatment to achieve the ultimate goal of urinary continence is needed in this population.

Overactive bladder in children

Overactive bladder (OAB) is a highly prevalent disorder in the pediatric population. This condition is especially troublesome for pediatric patients and their families when associated with incontinence, since it negatively affects self-esteem and impairs children's development. From the patient's perspective, urgency and urge incontinence can have a significant impact, negatively affecting their quality of life. For a therapy to have true benefit, changes must not only be statistically significant, but must also be perceived as meaningful by the patient. A stepwise approach is favoured to treat this pathology, starting with behavioural therapy, followed by medical management, and eventually more invasive procedures. Antimuscarinic agents are the mainstay of medical treatment for OAB. Oxybutynin is the most commonly used antimuscarinic in the pediatric population. However, some patients have a suboptimal response to antimuscarinics and many experience bothersome side effects, which have been documented with all antimuscarinics to a significantly higher degree than placebo. Although there have been reports about the use of tolterodine, fesoterodine, trospium, propiverine, and solifenacin in children, to date, only oxybutynin has been officially approved for pediatric use by medical authorities in North America. This review will address alternative treatment options for pediatric patients presenting with OAB, from conservative measures to more invasive therapies.

Histopathologic and Urodynamic Effects of the Anticholinergic Drugs Oxybutynin, Tolterodine, and Trospium on the Bladder

OBJECTIVES

This study aimed to evaluate the effects of intravesical instillation of the anticholinergic drugs oxybutynin, tolterodine, and trospium on bladder capacity and histopathological changes in the bladder mucosa.

METHODS

The study included 20 male New Zealand white rabbits that were randomly allocated to four groups of five. In the oxybutynin, tolterodine, and trospium groups, the drugs used were 1 mg/kg of crushed tablet mixed with 5 mL of saline, instilled intravesically once per day for 4 weeks. The control group was administered only 5 mL of saline once per day for 4 weeks. Urodynamic measurement of the bladder was made before and after treatment. At the end of the treatment the animals were killed and the bladders were evaluated histopathologically.

RESULTS

There were no significant differences between pre- and post-treatment bladder capacity in any of the groups (P > 0.05). Histopathological evaluation showed that the mucosal epithelium was intact and there was minor inflammation in the control group and oxybutynin group (P > 0.05), whereas there was destruction of the mucosal epithelium and findings of diffuse inflammation in the tolterodine (P = 0.014) and trospium (P = 0.014) groups.

CONCLUSION

Intravesical oxybutynin treatment was observed to be safe; however, a single daily dose of oxybutynin may not be sufficient to increase bladder capacity. Intravesical use of trospium and tolterodine at high doses caused epithelial destruction and diffuse inflammation in the bladder mucosa. The irritation associated with epithelial destruction and inflammation prevented an increase in bladder capacity.

Efficacy, safety, and tolerability of intravesically administered 0.1% oxybutynin hydrochloride solution in adult patients with neurogenic bladder: A randomized, prospective, controlled multi-center trial

AIMS

To verify the efficacy, safety and tolerability of intravesical administration of 0.1% oxybutynin hydrochloride compared to its oral administration for treatment of neurogenic detrusor overactivity (NDO) in a randomized, prospective, controlled, open-label, multi-center trial in 35 adult patients.

METHODS

NDO was confirmed within the previous 24 months by urodynamic studies (UDS). Group 1 (n = 18) received 10 ml 0.1% oxybutynin hydrochloride intravesically three times per day and group 2 (n = 17) 5 mg oxybutynin hydrochloride orally three times per day for a period of 28 days. Primary efficacy criterion was the change in the maximum bladder capacity between the beginning of the study and after 4 weeks as assessed by UDS. Adverse drug reactions (ADR) were collected and an evaluation of anticholinergic effects was conducted.

RESULTS

The increase in maximum bladder capacity was 117 ml with intravesical application (P = 0.0002) versus 18 ml with the oral application (P = 0.51). The difference was statistically significant (P = 0.0086). ADR were reported by 10 (55.6%) of patients with intravesical administration, and by 14 (82.4%) of patients with oral administration. Significant differences in favor of the intravesical application were observed in ADR affecting vision (1/10 vs. 9/14), gastrointestinal tract (8/10 vs. 14/14), nervous system (2/10 vs. 8/14), and skin and subcutis (1/10 vs. 6/14). No serious adverse drug reactions were reported.

CONCLUSIONS

This study demonstrates the efficacy and safety of intravesical 0.1% oxybutynin hydrochloride in the treatment of NDO with respect to the increase in maximum bladder capacity. Neurourol. Urodynam. 35:582-588, 2016. © 2015 Wiley Periodicals, Inc.

Pharmacokinetics and Pharmacodynamics of Once-Daily Controlled-Release Oxybutynin and Immediate-Release Oxybutynin

Oxybutynin is used to treat patients with urinary urgency, frequency, and urge incontinence. In this 2-way, multiple-dose, crossover study, the pharmacokinetics and pharmacodynamics of once-daily controlled-release oxybutynin were compared with immediate-release oxybutynin. Eighteen healthy male volunteers received one 15-mg controlled-release oxybutynin tablet once daily for 5 days or one 5-mg immediate-release oxybutynin tablet every 8 hours for 5 days. The washout period between treatments was > or =7 days. The mean steady-state AUC for oxybutynin following controlled-release oxybutynin treatment was higher (73.0 ng.h/mL) than following immediate-release oxybutynin treatment (53.6 ng.h/mL) (P = .0001). The mean C(max) was lower for controlled-release oxybutynin (5.7 ng/mL) than for immediate-release oxybutynin (7.5 ng/mL) (P = .0051), with a smaller fluctuation in oxybutynin plasma concentration for controlled-release oxybutynin (135.6%) than for immediate-release oxybutynin (319.3%) (P = .0001). Mean stimulated saliva output was greater for controlled-release oxybutynin, and mean dry mouth severity was less than immediate-release oxybutynin.

The evolution of transdermal therapy for overactive bladder

Oxybutynin chloride has been effectively used for treating overactive bladder syndrome for more than three decades. The evolution of different delivery systems led first to intravesical administration, anal suppositories, and then to the commercial development of an extended-release oral formulation of oxybutynin chloride to improve its tolerability while maintaining efficacy. These modes of delivery were associated with decreased antimuscarinic side effects and N-desethyloxybutynin serum levels by avoiding first-pass metabolism in the upper gut and liver. The development of transdermal delivery has carried this evolution even further, with serum levels of desethyloxybutynin < or = oxybutynin and dry mouth rates of 7%, with little constipation. The new development of a transdermal oxybutynin gel has decreased these application site reactions to low levels while maintaining good efficacy.

Efficacy and safety of transdermal and oral oxybutynin in children with neurogenic detrusor overactivity

PURPOSE

We evaluated the efficacy and safety of transdermal and oral oxybutynin in children with neurogenic detrusor overactivity.

MATERIALS AND METHODS

Children with neurogenic detrusor overactivity 6 to 15 years old and previously receiving oxybutynin were assigned randomly at a 3:1 ratio to treatment with transdermal or oral oxybutynin. Initial dosages (transdermal 1.3, 2.9 or 3.9 mg daily; oral 5, 10 or 15 mg daily), based on pre-study dosages, were adjusted after 2 weeks and then maintained for 12 weeks. The primary efficacy end point was change from baseline to last observation in average urine volume collected by clean intermittent catheterization.

RESULTS

A total of 57 patients were randomized to receive transdermal (41) or oral (16) oxybutynin. Safety data were available for 55 patients and efficacy data were available for 52. Mean +/- SD urine volume increased from 95 +/- 64 ml to 125 +/- 74 ml (p <0.001) with transdermal oxybutynin and from 114 +/- 75 ml to 166 +/- 92 ml (p = 0.002) with oral oxybutynin. Transdermal oxybutynin resulted in significant improvement in all measured urodynamic parameters. Similar trends and a significant increase in maximal cystometric bladder capacity were observed in the smaller oral oxybutynin group. There were 12 treatment related adverse events noted with transdermal oxybutynin (mild skin reaction) and 1 with oral oxybutynin (vasodilatation). The ratio of N-desethyloxybutynin-to-oxybutynin plasma concentrations was substantially lower with transdermal (1.4) than with oral (6.7) oxybutynin.

CONCLUSIONS

Transdermal oxybutynin was a well tolerated and effective alternative to oral oxybutynin in treating neurogenic detrusor overactivity in children who previously tolerated oxybutynin.

Intravesical oxybutynin for children with poorly compliant neurogenic bladder: a systematic review

PURPOSE

Children with neurogenic bladder and poor bladder compliance are usually treated with bladder catheterization and oral anticholinergic medication. They may become nonresponders to the drug or present with severe side effects. We evaluated the effectiveness and tolerability of intravesical oxybutynin in children with poorly compliant neurogenic bladder.

MATERIALS AND METHODS

We conducted a search of MEDLINE, EMBASE, CINAHL, SciELO, dissertations/theses in ProQuest, LILACS, the Cochrane Library, protocol registries and the gray literature. Two reviewers independently assessed study quality and extracted data.

RESULTS

Eight studies (2 prospective, 6 retrospective) assessed the effectiveness and side effects of intravesical oxybutynin in children with neurogenic bladder. A total of 297 children started treatment, of whom 22% (66 patients) discontinued therapy, with 9% (28) quitting due to systemic side effects. Mean change in bladder compliance (primary outcome) was reported in only 2 studies (+7.4 and +7.5 ml/cm H(2)O). The pooled mean change in pressure at maximum bladder capacity was -16.4 cm H(2)O (95% CI -22.8 to -10.0). Incontinence improved significantly in most studies, with "dry and improved" rates ranging from 61% to 83%. The funnel plot of pressure at maximum bladder capacity suggested no publication bias.

CONCLUSIONS

Adjunctive intravesical oxybutynin therapy increased mean maximum bladder capacity and decreased bladder pressure in children with neurogenic bladder. However, identified studies offered a low level of evidence, with most being poorly reported retrospective case series with potential biases. Although the incidence of side effects was lower with the intravesical route, side effects are still possible and should be discussed with patients and families. The evidence available is insufficient to recommend this therapy. Research of more sound study design such as a randomized controlled trial should be conducted to assess the efficacy and side effects of intravesical oxybutynin in children.

Treatment with modified intravesical oxybutynin chloride for neurogenic bladder in children

OBJECTIVE

We have previously reported that intravesical oxybutynin chloride with hydroxypropylcellulose (modified intravesical oxybutynin) is an effective therapeutic agent for patients with detrusor overactivity. In this study, we report on the efficacy, safety and side effects of modified intravesical oxybutynin administration in children with neurogenic bladder.

PATIENTS

Modified intravesical oxybutynin (1.25mg/5 mL, twice a day) was administered to four children (three males and one female) with neurogenic bladder (detrusor overactivity and/or low compliance bladder), who were previously unresponsive to or experienced intolerable side effects from oral medications. A cystometrogram was obtained before, 1 week after, and 1 year after the first intravesical instillation of modified oxybutynin. We also carefully observed anticholinergic side effects, occurrence of urinary tract infection and degree of incontinence during this treatment.

RESULTS

After 1 week, both cystometric bladder capacity and compliance were improved in all patients, and detrusor overactivity was undetectable in three of four patients. At 1 year, there was further improvement in bladder compliance in three patients, and detrusor overactivity was not observed in two patients. Significant improvement in the degree of incontinence was achieved. No systemic anticholinergic side effects were observed in any of the patients. One patient with vesicoureteral reflux discontinued the therapy after 2 months due to upper urinary tract infections.

CONCLUSION

Modified intravesical oxybutynin is an effective and relatively safe therapeutic option for children with neurogenic bladders.

The effects of tolterodine on bladder-filling sensations and perception thresholds to intravesical electrical stimulation: method and initial results

OBJECTIVES

To study the effects of the antimuscarinic agent tolterodine on the perception thresholds to intravesical electrical stimulation (IES) and the effects of the drug on subjective bladder sensation during normal filling cystometry in healthy female volunteers.

SUBJECTS AND METHODS

In seven healthy women IES was applied at 2.5 Hz (pulse width 10 ms, protocol 1), 2.5 Hz (pulse width 0.2 ms, protocol 2), and 250 Hz (pulse width 0.2 ms, protocol 3). Sensory perception thresholds were obtained using electric currents in 0.5 mA steps. Afterwards the bladder was filled and the first bladder-filling sensation, first desire to void, strong desire to void and urge to void were recorded. The bladder was then emptied, the volume measured and subjects were checked for residual urine by ultrasonography. The subjects then received 4 mg of tolterodine and the entire protocol was repeated 2 h afterward. The perception thresholds for IES and bladder sensation levels obtained at baseline were compared statistically with the corresponding values after tolterodine.

RESULTS

Tolterodine significantly increased perception thresholds to IES for all three protocols (P = 0.027, 0.018 and 0.018, respectively). The drug had no effect on the filling levels for the corresponding bladder sensation.

CONCLUSION

Oral tolterodine significantly increased the perception threshold to IES in healthy women; there was no effect on subjective bladder sensations during cystometry.

The durability of intravesical oxybutynin solutions over time

PURPOSE

Intravesical oxybutynin is prescribed for patients who do not tolerate the side effects of oral intake. Standard oral tablets are broken up, dissolved and instilled. For convenience some families create a large volume of solutions to use for weeks. We investigated the stability of oxybutynin concentration in these solutions and the effect of varying solvents and solutes.

MATERIALS AND METHODS

Solutions of oxybutynin were created with a starting concentration of 125 mug/ml. We varied the method of pill preparation (crushed vs passive dissolution), type of solvent (tap water vs normal saline) and the presence of the commonly instilled antibiotic, gentamicin sulfate (0.48 mg/ml). Solutions were aged for 1 to 4 weeks. Concentrations of oxybutynin were measured by gas chromatography.

RESULTS

Tap water as a solvent had the greatest decrease in concentration, declining below 50% by week 2 and reaching 25% by week 4. The mean concentration of the other solutions decreased less, maintaining 80% of the starting concentration at week 4. The use of normal saline as a solvent and the addition of gentamicin sulfate helped slow the decrease. Crushing vs passive dissolution showed no effect.

CONCLUSIONS

Homemade oxybutynin solutions degrade with time. Tap water solvent alone should be avoided. Solutions and additives that lower pH and are more acidic help oxybutynin solubility and stability. Storing oxybutynin solutions for later intravesical use appears feasible up to 4 weeks. The clinical effect of the 20% degradation remains to be demonstrated.

Transdermal drug delivery treatment for overactive bladder

Overactive bladder is commonly treated with oral anticholinergic drugs such as oxybutynin chloride. Although oral anticholinergic agents have been effective in controlling urinary urgency and incontinence, adverse events, particularly dry mouth, often cause patients to discontinue oral therapy and to endure incontinence. Oxybutynin can be delivered transcutaneously, maintaining the efficacy of oral oxybutynin while significantly minimizing side effects (e.g., dry mouth) that may complicate therapy. By avoiding hepatic and gastrointestinal metabolism of oxybutynin, less N-desethyloxybutynin (N-DEO) is produced and this compound is deemed to be responsible for anticholinergic side effects such as dry mouth. This novel oxybutynin formulation offers patients with OAB and urge urinary incontinence a well-tolerated option for managing the symptoms of overactive bladder.

Intravesikale Therapie des Overactive-bladder-Syndroms

Overactive bladder and urgency incontinence are common conditions generally treated with oral anticholinergic medication. Despite the development of new antimuscarinic substances, many patients are refractory to or cannot tolerate the oral therapy due to severe side effects. Intravesical instillation therapy can provide an alternative method to manage detrusor overactivity. Intravesical instillation of anticholinergics such as oxybutynin and trospium chloride can achieve cholinergic blockade without producing systemic side effects. Botulinum toxin type A injections into the detrusor have been shown to increase bladder capacity and to decrease detrusor overactivity for 6 or more months. Intravesical local anesthetics such as lidocaine and bupivacaine block the conduction of unmyelinated C fibers which results in an increase of functional bladder capacity. Intravesical capsaicin and resiniferatoxin also affect the afferent C fiber innervation of the bladder, leading to a decrease in detrusor overactivity and also an increased bladder capacity. The use of intravesical anticholinergics and of local anesthetic medications, both known for their short-term efficacy, is limited due to the necessity of daily intermittent catheterization. In conclusion, intravesical therapies can provide an alternative treatment for the management of overactive bladder.

Management of overactive bladder and urge urinary incontinence in the elderly patient

The symptoms of overactive bladder (OAB) and urge urinary incontinence may occur at any age but are particularly common among the elderly. These symptoms are associated with significant morbidity and often have a profound impact on patient quality of life. Urinary incontinence is an important contributor to the complications and economic cost of OAB for both community-dwelling and institutionalized elderly individuals. Many patients with OAB do not seek treatment because of embarrassment, fear of surgery, or the misperceptions that the problem is untreatable or is a normal and inevitable consequence of aging. Nonpharmacologic therapies improve bladder control by modifying lifestyle and behavior to prevent urine loss. This requires patient and caregiver motivation and can be time consuming. Improved results may be obtained by combining these strategies with pharmacotherapy or by means of pharmacotherapy alone. The most commonly used pharmacologic agents are the muscarinic receptor antagonists. These include oxybutynin, tolterodine, and three agents that have recently been approved for use in the United States: trospium, darifenacin, and solifenacin. In general, these therapies are well tolerated and safe; however, the selection of an optimal agent merits careful consideration. For elderly patients, important considerations include tolerability, absence of drug interactions, and the availability of a range of dosages to tailor treatment to individual patients. Primary care practitioners and geriatricians can have a key role in successful diagnosis and treatment of OAB. It is important for these physicians to realize that satisfactory outcomes may be achieved within the scope of a busy outpatient practice.

Intravesikale Therapie der überaktiven Blase

INTRODUCTION

Despite recent advances in the field of anticholinergic drugs, lack of efficiency and side effects are still the main reasons for discontinuation of treatment. The introduction of botulinum A toxin was a milestone in the treatment of detrusor overactivity. The treatment, however, is invasive, the duration of the treatment effects is limited, and long-term results are not yet available. The following addresses therapeutic alternatives to local treatment of overactive bladder.

MATERIALS AND METHODS

A total of 52 patients received intravesical oxybutynin. In 16 patients, capsaicin was instilled in the bladder and 28 patients were treated with EMDA.

RESULTS

Intravesical oxybutynin was successful in 86%; the success rate of capsaicin instillation was 47%. EMDA was successful in 78%. Two transient ischemic attacks following EMDA were observed as significant side effects.

CONCLUSION

Besides botulinum A toxin, several effective treatment options are available for patients with detrusor overactivity refractory to oral anticholinergic treatment. Therefore, in each individual patient, possible risks and complications of the different treatment options should be considered thoroughly to find the optimal method in each case.

Urodynamic effects of propiverine hydrochloride in children with neurogenic detrusor overactivity: a prospective analysis

OBJECTIVES

To evaluate prospectively the efficacy and tolerability of propiverine for treating neurogenic detrusor overactivity (NDO) in children.

PATIENTS AND METHODS

Twenty children (mean age 8.9 years; median 5.6) with NDO due to an upper motor neurone lesion were enrolled (17 had myelomeningocele). In the urodynamic examination, reflex volume (RV), maximum detrusor pressure (MDP), maximum cystometric bladder capacity (MCBC) and bladder compliance (BC) before and after a twice-daily propiverine hydrochloride regimen were determined. The urodynamic follow-up was after 3-6 months. Incontinence was assessed by an incontinence score.

RESULTS

The mean (sem) RV increased from 103.8 (21.3) to 174.5 (33.7) mL (P < 0.005), MDP decreased from 52.5 (7.9) to 40.1 (6.2) cmH(2)O (P < 0.05), MCBC increased from 166 (28.8) to 231.9 (34.8) mL (P < 0.005), and BC improved from 11.2 (2.8) to 30.6 (9.7) mL/cmH(2)O (P < 0.01), with propiverine treatment. The incontinence score (scale 0-3) improved from 2.4 (0.2) to 1.6 (0.3) (P < 0.05). Propiverine was well tolerated, although some children were given higher doses than recommended.

CONCLUSIONS

Propiverine hydrochloride is effective and well tolerated in the treatment of children with NDO. Because of its dual mode of action, it is well tolerated even in children who need higher doses. Propiverine hydrochloride is a preferable alternative to oxybutynin, the anticholinergic most frequently used in children with NDO to date.

Intravesical Therapy for Overactive Bladder

Overactive bladder and urgency incontinence are common conditions generally treated with oral anticholinergic therapy. Despite the development of new antimuscarinic agents, many patients do not tolerate or fail to respond to oral therapy. Intravesical instillation therapy can provide an alternative method of managing bladder overactivity. Intravesical instillation of anticholinergics such as oxybutynin and atropine can achieve cholinergic blockade without producing systemic side effects. Botulinum A toxin injected directly into the detrusor has been shown in preliminary studies to increase bladder capacity and decrease uncontrolled bladder contractility for up to 6 months. Intravesical local anesthetics such as lidocaine and bupivacaine block the conduction of unmyelinated C fibers and when administered into the bladder, lead to an increase in functional bladder capacity. Intravesical capsaicin and resiniferatoxin also affect afferent innervation by blocking C-fiber afferents, leading to decreased bladder contractility and increased bladder capacity. Intravesical instillation therapy can provide an alternative treatment for the management of overactive bladder.

Newer pharmacologic options in management of overactive bladder syndrome

PURPOSE OF REVIEW

Urinary incontinence is an under-reported epidemic that currently affects an estimated 13 million people in the United States, of whom about 11 million are women, according to the National Institute of Diabetes and Digestive and Kidney Diseases (Publication No. 02-4132). Because many patients are unaware of curative options and perceive it to be an inevitable outcome of advancing age, they fail to report their symptoms and increase their risk of developing associated co-morbid disease. Failure to diagnose and treat this condition increases financial burdens on individuals, their families and health care organizations.

RECENT FINDINGS

Pharmacologic therapy of urge incontinence previously had limited treatment success because efficacious drugs were poorly tolerated, resulting in low patient compliance. Tolerance and effectiveness continue to be improved due to innovative new drugs and alternative delivery systems.

SUMMARY

The goal of this review is to update the clinician on the efficacy and the tolerability of established and investigational pharmacologic modalities of therapy.

Update on the role of anticholinergic drug therapy in the management of overactive bladder

OBJECTIVE

To review the published literature and describe the pathophysiology and management of overactive bladder (OAB), with emphasis on the comparative efficacy and adverse event profiles of anticholinergic agents approved for the management of OAB symptoms and evaluation of their place in therapy.

DATA SOURCES

A MEDLINE search of English language literature that addresses the pathophysiology and management of OAB symptoms. The references in identified articles were evaluated for additional relevant articles. Drug Topics' Red Book was referenced for cost comparisons, and package inserts were used for specific drug and dosing information.

STUDY SELECTION

Human studies that presented efficacy and safety data with respect to anticholinergic medications in the treatment of OAB were selected.

DATA EXTRACTION

Studies were abstracted to identify key characteristics with respect to efficacy and safety in OAB, in particular anticholinergic side effects, with the greatest weight given to studies that compared two or more anticholinergic medications.

DATA SYNTHESIS

Epidemiologic studies have shown that the unpredictable and bothersome symptoms associated with OAB occur in approximately 16% of the worldwide adult population. Conservative management of OAB should include a combination of pharmacologic and nonpharmacologic interventions that have been found to improve outcomes when used in appropriately selected patients. Although long recognized as the most effective pharmacotherapy for OAB, anticholinergic agents have been associated with poor tolerability attributable to anticholinergic adverse events. New medications, formulations, and drug delivery systems have been developed with the goal of achieving effective treatment with improved tolerability.

CONCLUSIONS

Among these agents, extended-release and transdermal formulations have improved tolerability while retaining at least comparable efficacy. More research is needed regarding other routes of administration and new drug entities that specifically target the pathologic mechanisms involved in OAB.

Influence of estradiol pretreatment on antimuscarinic action of oxybutynin in rat detrusor muscle

OBJECTIVES

To investigate the antimuscarinic effect of oxybutynin in the rat detrusor muscle after estrogen pretreatment because, to our knowledge, no study has been done on the interaction of estrogen with antimuscarinic drugs. Estrogen has been shown to affect muscarinic receptors in the detrusor muscle of animals. In addition, oxybutynin has been shown to block muscarinic receptors in the bladder.

METHODS

Estradiol benzoate (150 microg/kg) or saline was given subcutaneously to virgin female Wistar albino rats (n = 6, each group) for 10 consecutive days. On the 11th day, isolated detrusor muscle strips were taken, and acetylcholine (ACh)-induced contractions were evaluated in the absence or presence of oxybutynin (10 and 100 nM).

RESULTS

ACh induced concentration-dependent contractions in the detrusor muscle. In the estradiol-pretreated group, the maximum of the ACh-induced contractions was diminished compared with that in the control group (P < 0.05). Oxybutynin (10 and 100 nM) inhibited ACh-induced contractions competitively (pK(B) 8.85). In the estradiol-pretreated group, the concentration-response curve to ACh was shifted further to the right in the presence of oxybutynin (100 nM).

CONCLUSIONS

We have demonstrated for the first time that oxybutynin further inhibits ACh-induced and muscarinic receptor-mediated contractions in rat detrusor muscle after pretreatment with estrogen.

Urodynamic effects and safety of modified intravesical oxybutynin chloride in patients with neurogenic detrusor overactivity: 3 years experience

BACKGROUND

Intravesical oxybutynin chloride with hydroxypropylcellulose (HPC) (modified intravesical oxybutynin) has been reported to be effective for treatment of overactive bladder. We reported the short-term effects of modified intravesical oxybutynin previously. In the present article, we detail the results of a 3-year follow-up study of patients from our previous analysis and report the efficacy and side-effects of modified intravesical oxybutynin.

METHODS

Modified intravesical oxybutynin (5 mg/10 mL, twice a day) was applied for more than 3 years to six neurogenic overactive detrusor patients (three men and three women, average age 53.3 years) who were not satisfied with oral anticholinergic agents or the other therapy. A cystometogram (CMG) was performed before, 1 week after and 3 years after the start of modified intravesical oxybutynin treatment. We evaluated the patient's satisfaction of this treatment after 4 weeks and again after 3 years. We compared the patients' answers before and after the therapy (excellent, good, fair, unchanged and worse). We also monitored systemic and topical side-effects in these patients during this period.

RESULTS

CMG studies showed that two of six patients no longer exhibited uninhibited contraction 1 week after the treatment and that the cystocapacity of patients before, 1 week after and 3 years after the initial modified intravesical oxybutynin was 129.7 +/- 19.4, 283.5 +/- 40.4 and 286.8 +/- 38.1 mL, respectively. For the evaluation of patients' satisfaction with this treatment, four patients considered the therapy excellent and one patient described it as good after both 4 weeks and after 3 years. Two patients dropped out of the study; one developed left ureteral cancer (2.25 years) and the other developed ileus (1.5 years). Dry mouth and acute cystitis were observed in both patients.

CONCLUSION

Modified intravesical oxybutynin is an effective and relatively safe option of therapy for overactive bladder patients. However, this therapy requires careful observation for emergent side-effects.

DEMONSTRATION OF BLADDER SELECTIVE MUSCARINIC RECEPTOR BINDING BY INTRAVESICAL OXYBUTYNIN TO TREAT OVERACTIVE BLADDER

PURPOSE

The current study was done to elucidate the in vivo mechanism of action of intravesical instillation of oxybutynin to treat overactive bladder.

MATERIALS AND METHODS

In rats receiving oral and intravesical oxybutynin we measured muscarinic receptors in the bladder and other tissues by radioligand binding assay using [3H]NMS ([N-methyl-3H] scopolamine methyl chloride) with the simultaneous measurement of plasma concentrations of oxybutynin and its active metabolite N-desethyl-oxybutynin. Pilocarpine induced salivary secretion was also measured.

RESULTS

Following oral administration of oxybutynin there was a significant increase in the apparent dissociation constant (Kd) for specific [3H]NMS binding in the bladder, submaxillary gland, heart and colon of rats at 1 and 3 hours with a consistent decrease in the maximal number of binding sites (Bmax) in the submaxillary gland. Furthermore, a marked and prolonged decrease in pilocarpine induced salivary secretion in rats was observed by oral oxybutynin. In contrast, intravesical instillation of oxybutynin produced a significant increase in Kd for specific [3H]NMS binding in the bladder of rats at 0.5 to 4 hours later and also in the submaxillary gland only at 0.5 hours later. The enhancement in Kd was much larger and longer lasting in the bladder than in the submaxillary gland. Moreover, intravesical oxybutynin had little muscarinic receptor binding activity in the heart and colon, and little significant suppression of pilocarpine induced salivation in rats. The plasma concentrations of oxybutynin and N-desethyl-oxybutynin were much higher in rats receiving oxybutynin orally than intravesically.

CONCLUSIONS

Intravesical oxybutynin in rats may cause selective binding of bladder muscarinic receptors via a direct local effect, while oral oxybutynin may exert predominant binding of salivary gland receptors.

Intravesical therapy options for neurogenic detrusor overactivity

STUDY DESIGN

Review article.

SETTING

Neuro-Urology, Spinal Cord Injury Center, Balgrist University Hospital, Zurich, Switzerland.

OBJECTIVES

This review considers intravesical treatment options of neurogenic detrusor overactivity and discusses the underlying mechanism of action, clinical safety and efficacy, and the future trends.

METHODS

The available literature was reviewed using medline services.

RESULTS

Oral anticholinergic drugs are widely used to treat detrusor overactivity, but they are ineffective in some patients or cause systemic side effects such as blurred vision or dry mouth. As an alternative, topical therapy strategies have been suggested to achieve a profound inhibition of the overactive detrusor and to avoid high systemic drug levels. Currently available intravesical treatment options either act on the afferent arc of the reflex such as local anaesthetics or vanilloids or on the efferent cholinergic transmission to the detrusor muscle such as intravesical oxybutynin or botulinum toxin. Although an established and effective therapy, intravesical oxybutynin is not widely used. Evidence for clinical significance of intravesical atropine and local anaesthetic is missing. Intravesical capsaicin has been shown to improve clinical and urodynamic parameters, but cause pain in some patients. The intravesical instillation of resiniferatoxin and the injection of botulinum-A toxin into the detrusor muscle are promising new options; however, randomised placebo-controlled studies to prove their safety and efficacy are still missing.

CONCLUSION

Intravesical treatment strategies in patients with neurogenic detrusor overactivity may provide alternatives to established therapies such as oral anticholinergics. The selectivity of the intravesical treatment and the reduction or even the absence of side effects are major advantages of this topical approach.

Clinical pharmacokinetics of drugs used to treat urge incontinence

Urge incontinence (also known as overactive bladder) is a common form of urinary incontinence, occurring alone or as a component of mixed urinary incontinence, frequently together with stress incontinence. Because of the pathophysiology of urge incontinence, anticholinergic/antispasmodic agents form the cornerstone of therapy. Unfortunately, the pharmacological activity of these agents is not limited to the urinary tract, leading to systemic adverse effects that often promote nonadherence. Although the pharmacokinetics of flavoxate, propantheline, scopolamine, imipramine/desipramine, trospium chloride and propiverine are also reviewed here, only for oxybutynin and tolterodine are there adequate efficacy/tolerability data to support their use in urge incontinence. Oxybutynin is poorly absorbed orally (2-11% for the immediate-release tablet formulation). Controlled-release oral formulations significantly prolong the time to peak plasma concentration and reduce the degree of fluctuation around the average concentration. Significant absorption occurs after intravesical (bladder) and transdermal administration, although concentrations of the active N-desethyl metabolite are lower after transdermal compared with oral administration, possibly improving tolerability. Food has been found to significantly affect the absorption of one of the controlled-release formulations of oxybutynin, enhancing the rate of drug release. Oxybutynin is extensively metabolised, principally via N-demethylation mediated by the cytochrome P450 (CYP) 3A isozyme. The pharmacokinetics of tolterodine are dependent in large part on the pharmacogenomics of the CYP2D6 and 3A4 isozymes. In an unselected population, oral bioavailability of tolterodine ranges from 10% to 74% (mean 33%) whereas in CYP2D6 extensive metabolisers and poor metabolisers mean bioavailabilities are 26% and 91%, respectively. Tolterodine is metabolised via CYP2D6 to the active metabolite 5-hydroxymethyl-tolterodine and via CYP3A to N-dealkylated metabolites. Urinary excretion of parent compound plays a minor role in drug disposition. Drug effect is based upon the unbound concentration of the so-called 'active moiety' (sum of tolterodine + 5-hydroxymethyl-tolterodine). Terminal disposition half-lives of tolterodine and 5-hydroxymethyl-tolterodine (in CYP2D6 extensive metabolisers) are 2-3 and 3-4 hours, respectively. Coadministration of antacid essentially converts the extended-release formulation into an immediate-release formulation. Knowledge of the pharmacokinetics of these agents may improve the treatment of urge incontinence by allowing the identification of individuals at high risk for toxicity with 'usual' dosages. In addition, the use of alternative formulations (controlled-release oral, transdermal) may also facilitate adherence, not only by reducing the frequency of drug administration but also by enhancing tolerability by altering the proportions of parent compound and active metabolite in the blood.

Pharmacokinetics, metabolism, and saliva output during transdermal and extended-release oral oxybutynin administration in healthy subjects

OBJECTIVE

To compare the pharmacokinetics and adverse effect dynamics of 2 modified-release oxybutynin treatments.

SUBJECTS AND METHODS

Between October 15 and November 6, 2001, 13 healthy subjects (7 men and 6 women) participated in a randomized, 2-way crossover study of transdermal (Oxytrol, 3.9 mg/d) and extended-release oral (Ditropan XL, 10 mg) oxybutynin. Multiple blood and saliva samples were collected. Pharmacokinetic parameters and total salivary output were assessed. Statistical analyses included 95% confidence intervals, paired t test, analysis of variance, and linear regression.

RESULTS

Steady-state plasma concentrations were achieved after the first transdermal application and after the second extended-release oral dose. Mean +/- SD 24-hour oxybutynin areas under the concentration-time curve were comparable during transdermal and oral extended-release treatments, 10.8 +/- 24 vs 9.2 +/- 33 ng x h(-1) x mL(-1), respectively. However, the ratio of area under the curve (N-desethyloxybutynin/oxybutynin) after transdermal administration (1.2 +/- 03) was significantly lower (P < .001) than after extended-release oral administration (4.1 +/- 0.9). Mean plasma concentrations were less variable during transdermal compared with extended-release oral administration. Mean +/- SD saliva output was greater during transdermal than extended-release oral treatment (15.7 +/- 93 vs 12.2 +/- 6.8 g, respectively; P = .02). Lower N-desethyloxybutynin during transdermal application was associated with greater saliva output (r = -059, P = .04). No clinically important treatment-related adverse effects were observed.

CONCLUSIONS

Transdermal oxybutynin administration results in greater systemic availability and minimizes metabolism to N-desethyloxybutynin compared with extended-release oral administration. Lower N-desethyloxybutynin plasma concentration and greater saliva output during transdermal treatment correspond to the reported low incidence of dry mouth in patients with overactive bladder.

Effectiveness of vaginally administered oxybutynin on rabbit bladder function

OBJECTIVES

To demonstrate the effectiveness of vaginally delivered oxybutynin on bladder function. Oxybutynin has been used for treatment of urge urinary incontinence for more than 20 years.

METHODS

Thirty female New Zealand White rabbits were used for this experiment. Each rabbit was anesthetized, and the carotid artery was cannulated for blood pressure monitoring. The bladder dome was catheterized for both monitoring of bladder pressure and cystometry. After initial cystometry, acetylcholine (ACh) was injected into the vesical artery at 15-minute intervals for 4 hours. Cystometry was performed at the 2-hour mark and at the end of each experiment (4 hours). After the third ACh administration, vaginal or oral oxybutynin was given and the effect on the response to ACh, blood pressure, and cystometry was observed.

RESULTS

The high dose of oxybutynin completely inhibited the response to ACh and significantly inhibited the micturition reflex. A 45% inhibition of micturition pressure occurred at the intermediate dose. Little effect on compliance after the low dose and a significant increase in compliance after the mid-dose occurred. Both the low and intermediate doses of oxybutynin reduced the response to ACh to approximately 50% of control. No blood pressure effects of vaginal oxybutynin were noted for any concentration. Oral oxybutynin showed very similar effects to that of the intermediate vaginal dose.

CONCLUSIONS

Vaginally delivered oxybutynin was effective in decreasing bladder compliance and inhibiting intra-arterial ACh-stimulated bladder contractions with little or no effect on the vascular effect of ACh.

Intravesical oxybutynin: a local anesthetic effect on bladder C afferents

PURPOSE

Intravesical oxybutynin is used to control bladder overactivity in patients who are refractory to or cannot tolerate oxybutynin given orally. Although it is clinically effective, the mode of action of intravesical oxybutynin remains unclear. We tested the influence of intravesical oxybutynin on single fiber pelvic nerve afferents from the rat bladder.

MATERIALS AND METHODS

A total of 15 single afferent bladder units were identified. Based on conduction velocity they were grouped as Adelta or C fibers. The effect of repeat bladder filling was studied on the mechanosensitive properties of these units. Oxybutynin was than instilled and left in the bladder for 15 minutes. Unitary afferent activity was again analyzed 15, 60 and 90 minutes after the drug was removed.

RESULTS

Repeat bladder filling did not change nerve activity in Adelta or C fibers. At 15 minutes after oxybutynin was washed out of the bladder C fiber afferents responded significantly less to intravesical pressure and volume compared with control filling. At 60 minutes C fibers partly regained mechanosensivity. After 90 minutes sensitivity still increased without achieving the response level before oxybutynin. No significant changes were noted in Adelta fibers during repeat bladder filling or after oxybutynin instillation.

CONCLUSIONS

In this study we showed that intravesical oxybutynin has a direct anesthetic effect within the bladder wall. It temporarily desensitizes C fiber afferents, which could explain its clinical benefits in decreasing symptoms of bladder overactivity. No measurable effect was found on Adelta fibers.

Neurological disorders cerebrovascular disease and parkinsonism

To store and expel urine at appropriate intervals, the lower urinary tract requires extensive input and control from the peripheral autonomic, somatic, and central nervous systems. Neurological disorders, such as cerebrovascular disease and Parkinson's disease, often cause functional disturbances of the lower urinary tract.

Pharmacokinetics and metabolism of transdermal oxybutynin: in vitro and in vivo performance of a novel delivery system

PURPOSE

The purpose of this work was to characterize in vitro/in vivo delivery and pharmacokinetics of oxybutynin (OXY) and its active metabolite. N-desethyloxybutynin (DEO), by a novel matrix transdermal system (TDS).

METHODS

Two in vivo, randomized, three-way crossover trials examined single/multiple OXY TDS doses. Abdomen, buttock, and hip application sites were compared and dose proportionality was evaluated. Model independent pharmacokinetics, elimination rate constants, and metabolite/drug ratios were derived from both plasma OXY and DEO concentrations.

RESULTS

Single/multiple applications of the OXY TDS to the abdomen yielded mean Cmax OXY concentrations of 3.4 +/- 1.1/6.6 +/- 2.4 ng/mL and median tmax of 36/10 h, with steady state achieved during the second application. Plasma OXY and DEO concentrations decreased gradually after Cmax until system removal. Buttock and hip applications resulted in bioequivalent OXY absorption. AUC ratios of DEO/OXY were 1.5 +/- 0.4 (single dose) and 1.3 +/- 0.3 (multiple dose). Mean in vitro OXY skin absorption (186 microg/h) was comparable to the estimated in vivo delivery (163 microg/h) over 96 h.

CONCLUSIONS

Sustained delivery over 4 days and multiple sites allow a convenient, well-tolerated, twice-weekly OXY TDS dosing. A low incidence of anticholinergic side effects is expected during clinical use because of the avoidance of presystemic metabolism and low DEO plasma concentrations. The consistent delivery, absorption, and pharmacokinetics should result in an effective treatment of patients with overactive bladder.

Conservative management in neurogenic bladder dysfunction

PURPOSE OF REVIEW

A few decades ago, urinary diversion, usually with an ileal conduit, was the ultimate outcome for most children with spina bifida. The revolutionary institution of clean intermittent catheterization has changed the algorithm totally. Furthermore many new drugs have been developed during the past decade and have decreased the need for surgery dramatically. In this article, we will focus on the most recent data on new modalities of therapy to help avoid urinary diversion or bladder augmentation.

RECENT FINDINGS

In addition to clean intermittent catheterization and oxybutynin treatment, a new generation of anticholinergic medications, such as tolterodine, has been developed. For patients who drop out because of the side-effects of oral administration, new methods of administration are now available, including extended release and intravesical instillation. For those unresponsive, botulinum-A toxin and resiniferatoxin are two relatively new drugs in the field, administered as intravesical injection and instillation, respectively. Intravesical or transdermal electrical stimulation, sacral nerve stimulation and biofeedback therapy are under development, but as currently administered, are not yet completely successful.

SUMMARY

Although life-saving in many respects, bladder augmentation introduces life-long risks of its own. Our goal in describing 'conservative' management is to prevent this step. Many alternatives to surgery are available now and more effective strategies are under development.

Oxybutynin chloride: alterations in drug delivery and improved therapeutic index

Oxybutynin chloride (Ditropan, Alza) is widely regarded as the most efficient antimuscarinic agent for the treatment of bladder detrusor dysfunction resulting in urinary urgency, frequency and urge incontinence. Oxybutynin metabolism occurs primarily in the proximal gastrointestinal tract and the hepatic circulation and is mediated by the cytochrome P450 3A4 isozyme. The major degradation products are desethyloxybutynin, which possesses pharmacological activity, and phenylcyclohexylglycolic acid, which is metabolically inert. A major limitation to long-term compliance with immediate-release oxybutynin remains the necessity for twice- or thrice-daily dosing regimens to provide sustained pharmacological efficacy. Side effects induced by cytochrome P450 metabolism of oxybutynin into the primary metabolite desethyloxybutynin within the gut wall substantially affect the tolerability of the compound within the individual. The oral osmotic delivery system provides unique advantages for drug delivery and substantially alters the tolerability profile of the oxybutynin chloride compound. This extended-release formulation consists of a two component core encapsulated by a semi-permeable membrane. The osmotic gradient between the surrounding environment and the inner core of the delivery system remains constant and water absorption within the capsule is controlled by the semipermeable membrane causing a controlled release of drug, which is sustained over 24 h. Herein are reviewed the various pre- and post-approval trials which have documented the overall therapeutic index of the oral osmotic oxybutynin (Ortho-McNeil Pharmaceuticals). Subsequent post-market surveillance issues are reviewed as are new developments in oxybutynin delivery.

Preliminary study of the safety and efficacy of extended-release oxybutynin in children

OBJECTIVES

To test the safety and efficacy of extended-release oxybutynin in children with bladder dysfunction. The efficacy of oxybutynin in children has been limited by side effects. A new extended-release formulation of oxybutynin has some benefits versus traditional oxybutynin but has never been evaluated in children.

METHODS

A retrospective study was performed on 25 children who had been treated with extended-release oxybutynin. Fourteen had neurogenic bladder dysfunction and 11 had urinary frequency and urgency and urge incontinence but no neurologic abnormalities. Patients and families were asked to semiquantitatively (0 to 10 grading with 10 = severe) assess the effects of the medication on efficacy, as well as side effects and compliance with medication schedules.

RESULTS

All 25 patients had improvement in incontinence and/or voiding dysfunction on extended-release oxybutynin. Twelve (48%) experienced no side effects. Of the 13 who did, 10 complained of dry mouth (grade 4.6 plus minus 0.5), 4 had constipation (grade 5.8 plus minus 1.8), 4 had heat intolerance (grade 5.1 plus minus 0.9), and 3 had drowsiness (grade 5.3 plus minus 2.4). Of patients previously treated with oxybutynin, the extended-release oxybutynin was equally or more efficacious and had the same or fewer side effects, especially less dry mouth. Families reported much better patient compliance with the medication regimen using extended-release oxybutynin compared with oxybutynin. Patient and family satisfaction was very high, and 21 of 25 have continued using the medication.

CONCLUSIONS

Extended-release oxybutynin is safe and efficacious in children. In this preliminary evaluation, it had benefits over traditional, immediate-release oxybutynin.

Intravesical oxybutynin affects bladder permeability

To investigate the effects of intravesical application of oxybutynin chloride on bladder permeability we designed an animal model. Female Guinea pigs were given 3 different test solutions: phosphate buffered saline (PBS), 50% acetone and 1.27 x 10(-2) M oxybutynin chloride solution. Then 99mTc-DTPA 45 microCi in 2 ml normal saline was instilled into the bladder lumen in each animals and allowed to dwell for 30 minutes. At the end of exposure time, the net count data in each 1 ml serum sample were corrected for radioactive decay and converted to the total percentage of administered dose. 99mTc-DTPA absorption percentages of both acetone and oxybutynin groups were significantly higher than that of PBS group (mean 3.2 +/- 2.9% p < 0.001). Intravesical oxybutynin application increases bladder permeability 5 times compared with PBS administration. This observation can also explain how rapid absorption of oxybutynin through the bladder into the systemic circulation occurs.

Pharmacokinetics of the R- and S-enantiomers of oxybutynin and N-desethyloxybutynin following oral and transdermal administration of the racemate in healthy volunteers

PURPOSE

To characterize the enantiomers of oxybutynin (OXY) and N-desethyloxybutynin (DEO) following transdermal and oral administration.

METHODS

OXY was administered either as a single transdermal system over a 96 h wear period or as a single 5 mg immediate-release tablet to 18 healthy male and female subjects in a randomized, open-label, two-way crossover design. Blood samples were collected for 108 h after application of the transdermal system and for 6 h after oral administration. Plasma concentrations of the R- and S-enantiomers of OXY and DEO were assayed by LC-MS/MS. Enantiomer in vitro skin flux was evaluated using human cadaver skin.

RESULTS

In vitro skin flux studies demonstrated equal absorption of R and S- OXY. Plasma concentrations and pharmacokinetic parameters of the R-enantiomers of OXY and DEO were slightly lower than the S-enantiomers following transdermal OXY. The relative AUC values were S-OXY>S-DEO>R-OXY>R-DEO. The AUC ratios of DEO/ OXY were less than 1 for both the R- and S- enantiomers. Following oral dosing, plasma DEO concentrations greatly exceeded OXY resulting in relative AUC values of R-DEO>S-DEO>S-OXY>R-OXY. The mean AUC ratios of S- and R-DEO/OXY were 3.25 and 8.93, respectively.

CONCLUSIONS

Stereoselective metabolism of OXY was evident following both transdermal and oral administration of OXY. The reduced pre-systemic metabolism of transdermally administered OXY compared to oral administration resulted in not only significantly lower DEO plasma concentrations, but also a different metabolite pattern. The differences between R-OXY and R-DEO following the two routes of administration support the potential for comparable clinical efficacy and reduced anticholinergic side-effects with transdermal treatment.

Side-effects of oral or intravesical oxybutynin chloride in children with spina bifida

OBJECTIVE

To evaluate the incidence of side-effects of oral and intravesical oxybutynin chloride in children with meningomyelocele (MMC) and a neurogenic bladder.

PATIENTS AND METHODS

The study comprised 225 children with a neurogenic bladder from MMC who were evaluated with urodynamic testing and voiding cysto-urethrography to identify those at high risk of upper tract damage. In all, 101 children (mean age 4.2 years, range 0.25-10) had unco-ordinated detrusor-sphincter function and low compliance; they were treated with either oral or intravesical oxybutynin and clean intermittent catheterization.

RESULTS

Of the 101 patients, 67 were treated with oral oxybutynin; in 11 the treatment was discontinued because of the side-effects. The other 34 patients used both clean intermittent catheterization and intravesical oxybutynin. In this group there were side-effects in six patients, including drowsiness, hallucinations and cognitive changes.

CONCLUSIONS

Oral and intravesical oxybutynin is effective for managing neurogenic bladder dysfunction, but intravesical administration is safer and better tolerated than oral oxybutynin in the treatment of children with MMC. However, adverse effects such as cognitive impairment can also occur in children treated with intravesical oxybutynin and these patients must be closely monitored because these effects may differ from those with oral administration.