Bioavailability of trospium chloride after intravesical instillation in patients with neurogenic lower urinary tract dysfunction: A pilot study

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.

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.

Advances in intravesical therapy for urinary tract disorders

INTRODUCTION

Intravesical therapy is a valuable option in the clinical management of urinary tract disorders such as interstitial cystitis/ painful bladder syndrome (IC/PBS) and refractory overactive bladder. This review will cover the latest advances in this field using polymer and liposomes as delivery platform for drugs, protein and nucleic acids.

AREAS COVERED

This review summarizes the significance of intravesical therapy for lower urinary tract disorders. The recent advancement of liposomes as a drug delivery platform for botulinum toxin, tacrolimus and small interfering RNA is discussed. The importance of polymers forming indwelling devices and hydrogels are also discussed, where all preparations improved efficacy parameters in rodent models. Clinical experience of treating IC/PBS with indwelling devices and liposomes are summarized and preclinical evidence about the downregulation of target gene expression in rodent bladder with liposomes complexed with siRNA is also reviewed.

EXPERT OPINION

There have been several advances in the field of intravesical therapy for improving clinical outcomes. One of the most promising research avenues is the repurposing of drugs, given previously by other routes of administration, such as tacrolimus. Intravesical therapy also opens up novel therapeutic targets with improved efficacy and safety for underactive bladder.

Urinary incontinence: pharmacotherapy options

The impact of incontinence is felt by millions of people worldwide, with tremendous decrement in quality of life and enormous cost reaching billions of dollars. Urinary incontinence is defined as 'involuntary leakage of urine' and is categorized into two main types: urgency urinary incontinence (UUI) and stress urinary incontinence (SUI). Behavioral modifications and pharmacologic therapies, primarily antimuscarinic agents, are the mainstay of treatment for UUI. These drugs are moderately efficacious but have troublesome side-effects, the combination resulting in poor compliance and persistence with therapy. There are several agents on the market today, each with some variation in pharmacologic properties. Whether these translate into meaningful differences in clinical efficacy and tolerability remains a matter of debate. Treatment of SUI has seen little success with pharmacologic therapy. In Europe, duloxetine is approved for treatment of SUI with marginal success rates; this drug, although available in the United States for treatment of depression, is not approved for SUI. The search for newer and better pharmacologic options and novel therapies is on-going, fueled primarily by the high prevalence of bothersome incontinence and the tremendous number of health care dollars spent on current therapy. This review addresses pharmacologic options for treatment of urinary incontinence.

Urothelial effects of oral agents for overactive bladder

The cholinergic system of the bladder includes muscarinic receptors distributed to detrusor myocytes and structures within mucosa including bladder afferent (sensory) nerves. The receptors have been shown to be involved in afferent signaling from the bladder, but it has not been established to what extent effects on this mucosal signaling pathway contribute to the therapeutic efficacy of the clinically used antimuscarinics. Mucosa can be influenced by antimuscarinics via the bloodstream. However, some antimuscarinics and their active metabolites are excreted in urine in amounts that may affect the mucosal muscarinic receptors from the luminal side. This has not yet been demonstrated to imply superior clinical efficacy. Nevertheless, mucosal afferent signaling pathways are therapeutically interesting targets that should be further explored.

Comparison of receptor binding characteristics of commonly used muscarinic antagonists in human bladder detrusor and mucosa

Recent studies have described muscarinic receptors on the mucosa and the detrusor of the human urinary bladder. Muscarinic receptor antagonists are effective in the treatment of overactive bladder (OAB), but their site(s) of action and actual therapeutic target are unclear. Our aim was to compare, in human bladder mucosa and detrusor, the radioligand binding characteristics of newer, clinically effective agents: darifenacin, its hydroxylated metabolite UK-148,993, fesoterodine, solifenacin, tolterodine, and trospium. Specimens were collected from asymptomatic patients (50-72 years old) undergoing open bladder surgery. Radioligand binding studies with the muscarinic antagonist [3H]quinuclidinyl benzilate (QNB) were performed separately on detrusor and mucosal membranes. All antagonists displayed high affinity when competing for [3H]QNB binding in both detrusor and mucosa. Inhibition constants were also obtained for all antagonists against individual muscarinic receptor subtypes expressed in Chinese hamster ovary cells. Here, fesoterodine showed anomalous binding results, suggesting that some conversion to its metabolite had occurred. Global nonlinear regression analysis of bladder binding data with five antagonists demonstrated 82% low-affinity sites in mucosa and 78% low-affinity sites in detrusor, probably representing M(2)/M(4) receptors. There was an excellent correlation (r(2) = 0.99) of low-affinity global estimates between detrusor and mucosa, whereas the corresponding high-affinity estimates ( approximately 20% of sites) were dissimilar. In conclusion, commonly used and clinically effective muscarinic receptor antagonists bind to receptors located on the bladder mucosa and the detrusor, providing support for the hypothesis that muscarinic receptors in the mucosa may represent an important site of action for these agents in OAB.

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.

Clinical pharmacokinetics of trospium chloride

Trospium chloride, a quaternary amine with anticholinergic properties, is used for the treatment of overactive bladder with symptoms of urge urinary incontinence, urgency and urinary frequency. The pharmacokinetics of trospium chloride have been investigated in healthy volunteers, in patients with renal and hepatic impairment, and in those with symptoms of overactive bladder, after oral, intravenous and intravesical administration. After oral administration, absorption of the hydrophilic trospium chloride is slow and incomplete. Peak plasma concentrations (Cmax) of approximately 4 ng/mL are reached 4-5 hours after administration of a 20 mg immediate-release preparation. The mean bioavailability is approximately 10% and decreases by concomitant food intake (to a mean of 26% of the fasting area under the plasma concentration-time curve [AUC]). Trospium chloride displays dose proportional increases in AUC and Cmax after a single dose within the clinically relevant dose range (20-60 mg). The mean volume of distribution is approximately 350-800 L. The drug is minimally (mean approximately 10%) metabolised to spiroalcohol by hydrolysis, is 50% plasma protein bound and does not cross the blood-brain barrier. Urinary excretion of the parent compound plays a major role in the disposition of the drug, with a mean renal clearance of 29 L/h (accounting for approximately 70% of total clearance) and a mean elimination half-life ranging from 10 to 20 hours. Elimination of the drug is slowed in patients with renal insufficiency, and population pharmacokinetic modelling has demonstrated that drug clearance is correlated with serum creatinine concentration. Thus, dose reduction is needed in patients with severe renal impairment (i.e. creatinine clearance < 30 mL/min). To date, no clinically relevant pharmacokinetic drug-drug interactions have been identified; the drug does not bind to any of the drug metabolising cytochrome P450 enzymes. The pharmacokinetics of the drug are compatible with twice-daily administration. A once-daily schedule may also be appropriate, but this regimen needs formal clinical evaluation.

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.

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.

Trospium chloride: A quaternary amine with unique pharmacologic properties

The mainstay of pharmacologic treatment of overactive bladder is anticholinergic therapy. Cholinergic blockade is efficacious in decreasing the symptoms of urgency, frequency, and urge incontinence, but also is associated with undesirable side effects such as dry mouth, blurred vision, constipation, and central nervous system side effects. The property of anticholinergic agents that has been associated with increased efficacy and tolerability is receptor specificity. The safety of anticholinergic agents has been associated with the pharmacokinetics, metabolism, protein binding, and ability to penetrate the blood brain barrier. Trospium chloride, available in Europe for more than 20 years and under review by the US Food and Drug Administration for the treatment of overactive bladder, is a quaternary amine that is minimally metabolized, not highly protein-bound, and theoretically should not cross the blood brain barrier. Some of the characteristics of this unique anticholinergic agent are reviewed in this article and the relative contributions of these factors are discussed.