Characterization of bladder selectivity of antimuscarinic agents on the basis of in vivo drug-receptor binding

Update on Overactive Bladder Therapeutic Options

BACKGROUND

Millions of Americans are burdened by overactive bladder (OAB) syndrome and the psychogenic and economic hardships that accompany it. Several theories attempt to explain OAB as a neurogenic dysfunction, myogenic dysfunction, urothelial dysfunction, or decreased expression of a channel protein secondary to bladder outlet obstruction. Given that the etiology of OAB is a working theory, the management of OAB is also an evolving subject matter in medicine. There are uncertainties surrounding the pathophysiology of OAB, the strength of a clinical diagnosis, and accurate reporting because of the disease's stigma and decreased use of health care.

DATA SOURCES

This is a narrative review that used PubMed, Google Scholar, Medline, and ScienceDirect to review literature on current and future OAB therapies.

RESULTS

Currently, first-line treatment for OAB is behavioral therapy that uses lifestyle modifications, bladder-control techniques, and psychotherapy. Second-line therapy includes antimuscarinic agents or beta 3 adrenergic agonists, and studies have shown that combination therapy with antimuscarinics and beta 3 adrenergic agonists provides even greater efficacy than monotherapy. Third-line therapies discussed include onabotulinumtoxinA, posterior tibial nerve stimulation, and sacral neuromodulation. OnabotulinumtoxinA has been FDA-approved as a nonpharmaceutical treatment option for refractory OAB with minimal side effects restricted to the urinary tract. Posterior tibial nerve modulation and sacral neuromodulation are successful in treating refractory OAB, but the costs and complication rates make them high-risk procedures. Therefore, surgical intervention should be a last resort. Estrogen therapy is effective in alleviating urinary incontinence in postmenopausal women, consistent with the association between estrogen deficiency and genitourinary syndrome. Potassium channel activators, voltage-gated calcium channel blockers, and phosphodiesterase inhibitors look to be promising options for the future of OAB management. As new therapies are developed, individuals with OAB can better personalize their treatment to maximize their quality of life and cost-effective care.

Predicting muscarinic receptor occupancy in human bladder mucosa from urinary concentrations of antimuscarinic agents for overactive bladder

To assess the pharmacologically relevant and selective muscarinic receptor occupancy in the bladder mucosa, we considered not only plasma drug concentrations but also urinary drug concentrations. The purpose of this study was to predict muscarinic receptor occupancy in the human bladder mucosa based on urinary concentrations in response to clinical dosages of antimuscarinic agents used to treat overactive bladder. The calculated mean plasma or serum unbound steady state concentrations were 0.06-11 nM in clinical dosages of five antimuscarinic agents. Urinary concentrations calculated from the mean plasma or serum and renal clearance ranged between 19 nM and 2 μM, which were >10-fold higher than the Ki values for bladder muscarinic receptors excluding propiverine. Bladder mucosal muscarinic receptor occupancy estimated from the urinary concentrations and the Ki values was >90 % at a steady state in clinical dosages of five antimuscarinic agents. The bladder muscarinic receptor occupancy was higher than that in the parotid gland calculated based on the mean plasma or serum unbound concentrations and Ki values for muscarinic receptors in the parotid gland. These results suggest that sufficient and selective muscarinic receptor occupancy by antimuscarinic agents, to exert pharmacological effects, in the bladder mucosa can be predicted using urinary concentrations.

Pharmcokinetic and pharmacodynamic considerations for the anticholinergic burden scale of drugs

Older adults frequently have many systemic diseases that require treatment with multiple drugs, and thus anticholinergic adverse effect by polypharmacy is a significant concern in the management of older adults. The accuracy of the anticholinergic burden rating may be increased by considering pharmacokinetic and pharmacodynamic factors such as biophase drug concentrations, the pharmacologically active metabolites formed after drug administration, and muscarinic receptor-mediated effects. Therefore, a pharmacological evidence-based burden scale that considers pharmacokinetic and pharmacodynamic factors is expected to be a more optimal tool for precisely assessing the anticholinergic burden, specifically risk reductions in anticholinergic adverse events in the poly-medicated elderly. Geriatr Gerontol Int 2024; 24: 81-87.

Cognitive effects of individual anticholinergic drugs: a systematic review and meta-analysis

Anticholinergics (ACs) are among the most prescribed drugs. Investigating the impaired cognitive domains due to individual ACs usage is associated with controversial findings.

Objective

The objective of this study was to investigate the effects of individual ACs on different aspects of cognitive function based on clinical trial studies.

Methods

This systematic review was conducted following the PRISMA statement. A systematic search was performed in Embase, PubMed, Cochrane Library, Scopus, and Web of Science databases. Risk of bias (RoB) was assessed by the Joanna Briggs Institute checklists and the meta-analysis was performed using the CMA software.

Results

Out of 3,026 results of searching, 138 studies were included. A total of 38 studies that assess the cognitive impacts of scopolamine were included in the meta-analysis. Included studies reported cognitive effects of scopolamine, mecamylamine, atropine, biperiden, oxybutynin, trihexyphenidyl, benzhexol, and dicyclomine; however, glycopyrrolate, trospium, tolterodine, darifenacin, fesoterodine, tiotropium, and ipratropium were not associated with cognitive decline. Based on the meta-analyses, scopolamine was associated with reduced recognition (SDM -1.84; 95%CI -2.48 to -1.21; p<0.01), immediate recall (SDM -1.82; 95%CI -2.35 to -1.30; p<0.01), matching to sample (SDM -1.76; 95%CI -2.57 to -0.96; p<0.01), delayed recall (SDM -1.54; 95%CI -1.97 to -1.10; p<0.01), complex memory tasks (SDM -1.31; 95%CI -1.78 to -0.84; p<0.01), free recall (SDM -1.18; 95%CI -1.63 to -0.73; p<0.01), cognitive function (SDM -0.95; 95%CI -1.46 to -0.44; p<0.01), attention (SDM -0.85; 95%CI -1.38 to -0.33; p<0.01), and digit span (SDM -0.65; 95%CI -1.21 to -0.10; p=0.02). There was a high RoB in our included study, especially in terms of dealing with possible cofounders.

Conclusion

The limitations of this study suggest a need for more well-designed studies with a longer duration of follow-up on this topic to reach more reliable evidence.

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.

A systematic review of neurocognitive dysfunction with overactive bladder medications

INTRODUCTION AND HYPOTHESIS

The aim of this study is to report cognitive dysfunction with commonly used antimuscarinic overactive bladder medications in patients suffering from overactive bladder disorder with and without baseline neurologic conditions.

METHODS

We conducted an Ovid MEDLINE, Embase, and PsycINFO search from January 1998 to December 2018 using PRISMA guidelines. Eighteen studies met the inclusion criteria, including 5 randomized controlled trials and 13 observational studies.

RESULTS

Cognitive decline was reported with oxybutynin use (5 of 8 studies) and tolterodine use (4 of 7 studies) among patients with and without baseline cognitive impairment. Oxybutynin use was linked to functional, mental, and behavioral decline among patients with Alzheimer's disease (2 studies). No cognitive decline was detected among patients with and without baseline cognitive impairment taking trospium (6 studies), darifenacin (3 studies), imidafenacin (2 studies), and fesoterodine (1 study). Solifenacin was not associated with cognitive decline (2 studies) but was linked to an increased risk of dementia among patients with diabetes (1 study).

CONCLUSION

In this review, cognitive decline was reported with oxybutynin and tolterodine use and should be used with caution in adults over 65 years of age. Solifenacin, fesoterodine, and imidafenacin showed mixed results related to central nervous system effect. Trospium and darifenacin were not associated with cognitive decline among patients with and without baseline cognitive impairment.

Is Combining an Anticholinergic with a Cholinesterase Inhibitor a Good Strategy for High-Level CNS Cholinesterase Inhibition?

The currently approved cholinesterase inhibitors (donepezil, rivastigmine, and galantamine) produce gastrointestinal toxicity which limits dosing to that which produces only about 25% to 35% CNS cholinesterase inhibition in Alzheimer's disease patients undergoing treatment, below the minimum therapeutic target of about 40% to 50% CNS inhibition considered necessary to treat cognitive impairment. A recent strategy for producing high-level CNS acetylcholinesterase (AChE) inhibition (50% or higher) is to co-administer a muscarinic anticholinergic with the AChE inhibitor to block the dose-limiting cholinergic overstimulation of the gastrointestinal system, allow more robust AChE inhibition in the CNS, and improve efficacy in the treatment of Alzheimer's disease. Unfortunately, most common muscarinic anticholinergics, including solifenacin, readily penetrate the CNS and are directly associated with long-term exacerbation of the underlying neuropathology of Alzheimer's disease and increased brain atrophy. The co-administration of an anticholinergic with an AChE inhibitor is a rational strategy for improving efficacy in the symptomatic treatment of dementia, but there are significant long-term risks that have not yet been considered. For long-term safety against accelerating the underlying disease processes in Alzheimer's disease, anticholinergics used to increase the tolerability of AChE inhibitors should not penetrate, or have very limited penetration, of the blood-brain barrier. Neurotrophic-mediated mechanisms by which cholinergic drugs may affect neurodegeneration in Alzheimer's disease are explored and improved treatment options are suggested.

Effects of combined treatment with fesoterodine and mirabegron in a pelvic congestion rat model: Results from in vitro and in vivo functional studies

Objectives

To examine the effect of combining a nonselective muscarinic receptor antagonist, 5‐hydroxymethyl tolterodine (an active metabolite of fesoterodine), with a β3 adrenoceptor agonist, mirabegron, in a rat model of pelvic congestion.

Methods

The rat pelvic congestion model used female Sprague‐Dawley rats with their bilateral common iliac and uterine veins ligated. Expressions of M2 and M3 receptor subtypes in the urothelium and detrusor were detected by real‐time polymerase chain reaction assays. The effects of both drugs were investigated on isolated bladder strips contracted by electrical field stimulation. in vivo single cystometry was used to assess the effects of 5‐hydroxymethyl tolterodine and mirabegron independently or in combination on bladder capacity, micturition pressure, and threshold pressure.

Results

Pelvic congestion rats showed decreased bladder capacity compared with controls, but micturition pressure and threshold pressure were unchanged. Pelvic congestion model rats also demonstrated an approximately two‐fold increase in expression of both M2 and M3 receptor subtypes in the urothelium. Additive relaxant effects of 5‐hydroxymethyl tolterodine and mirabegron were observed in vitro in the electrical field stimulation‐induced contractions of bladder strips from pelvic congestion rats. In vivo, bladder capacity was increased significantly by a combination of 5‐hydroxymethyl tolterodine and mirabegron, with the combined effect exceeding the sum of the effects of monotherapies. Micturition pressure and threshold pressure did not significantly differ between groups.

Conclusions

The combination of 5‐hydroxymethyl tolterodine with mirabegron suggests the potential of synergistic effects in a rat pelvic congestion model.

Bioanalytical method for quantification of Solifenacin in rat plasma by LC-MS/MS and its application to pharmacokinetic study

Background

Solifenacin succinate is a competitive muscarinic acetylcholine receptor antagonist used in the treatment of overactive bladder with or without urge incontinence.

Methods

Liquid chromatography–tandem mass spectrometry method was used for quantification of Solifenacin (SF) in rat plasma. Solifenacin-d5 (SFD5) used as an internal standard. Chromatographic separation was performed Gemini-NX C18, 50 × 4.6 mm, 5 µm, 110 Å column. Mobile phase composed of 5 mM Ammonium formate, pH 3.0: methanol (20:80 v/v), with 0.4 mL/min flow-rate. Drug and IS were extracted by Liquid- liquid extraction method. SF and SFD5 were detected with proton adducts at m/z 363.2®193.2 and 368.2®198.2 in multiple reaction monitoring (MRM) positive mode respectively. The method was validated with the correlation coefficients of (r2) ≥ 0.9975 over a linear concentration range of 0.1-100.0 ng/mL.

Results

This method demonstrated intra and inter-day precision within 1.09 to 4.84 and 1.75 to 7.68 % and accuracy within 101.21 to 106.67 and 97.94 to 104.79 % for SF.

Conclusions

This method is successfully applied in the Pharmacokinetic study of rat plasma.

Muscarinic receptors mediate cold stress-induced detrusor overactivity in type 2 diabetes mellitus rats

OBJECTIVES

This study determined if muscarinic receptors could mediate the cold stress-induced detrusor overactivity induced in type 2 diabetes mellitus rats.

METHODS

Ten-week-old female Goto-Kakizaki diabetic rats (n = 12) and Wister Kyoto non-diabetic rats (n = 12) were maintained on a high-fat diet for 4 weeks. Cystometric investigations of the unanesthetized rats were carried out at room temperature (27 ± 2°C) for 20 min. They were intravenously administered imidafenacin (0.3 mg/kg, n = 6) or vehicle (n = 6). After 5 min, the rats were transferred to a low temperature (4 ± 2°C) for 40 min where the cystometry was continued. The rats were then returned to room temperature for the final cystometric measurements. Afterwards, expressions of bladder muscarinic receptor M3 and M2 messenger ribonucleic acids and proteins were assessed by reverse transcription polymerase chain reaction and immunohistochemistry.

RESULTS

In non-diabetic Wister Kyoto rats, imidafenacin did not reduce cold stress-induced detrusor overactivity. In diabetic Goto-Kakizaki rats, just after transfer to a low temperature, the cold stress-induced detrusor overactivity in imidafenacin-treated rats was reduced compared with vehicle-treated rats. Within the urinary bladders, the ratio of M3 to M2 receptor messenger ribonucleic acid in the diabetic Goto-Kakizaki rats was significantly higher than that of the non-diabetic Wister Kyoto rats. The proportion of muscarinic M3 receptor-positive area within the detrusor in diabetic Goto-Kakizaki rats was also significantly higher than that in non-diabetic Wister Kyoto rats.

CONCLUSIONS

Imidafenacin partially inhibits cold stress-induced detrusor overactivity in diabetic Goto-Kakizaki rats. In this animal model, muscarinic M3 receptors partially mediate cold stress-induced detrusor overactivity.

Factors influencing patient satisfaction with antimuscarinic treatment of overactive bladder syndrome: results of a real-life clinical study

OBJECTIVES

To investigate patient satisfaction with antimuscarinic treatment of overactive bladder syndrome, and to identify factors having a significant influence on satisfaction.

METHODS

A cross-sectional questionnaire survey was carried out to assess treatment satisfaction among male and female patients with overactive bladder (age ≥20 years) in the Hokuriku district of Japan. The overactive bladder symptom scores, treatment efficacies, adverse events (dry mouth and constipation), and patient satisfaction scores were investigated and compared among patients using different antimuscarinic therapeutics.

RESULTS

In total, 977 survey respondents (52.6% men; mean age 73.6 years) received antimuscarinic treatment. The mean overactive bladder symptom score of these patients was 6.17; in addition, 32.3% patients were satisfied with their treatment, but 33.1% were dissatisfied. Factors having a significant influence on treatment satisfaction were sex (men were less satisfied), efficacy, adverse events and the overactive bladder symptom score. Constipation negatively influenced patient satisfaction to a greater extent than did dry mouth. Patient satisfaction varied according to the drug used. Constipation was less severe with the immediate-release-type agents (imidafenacin and oxybutynin) than with the extended-release-type (propiverine, solifenacin or tolterodine).

CONCLUSIONS

Just one-third of Japanese Hokuriku patients with overactive bladder seem to be satisfied with their antimuscarinic treatment. Patient satisfaction is impaired by poor efficacy and the presence of adverse events; furthermore, constipation should be recognized as an adverse event that negatively influences patient satisfaction to a greater extent than dry mouth. Patient satisfaction differs according to the antimuscarinic agent used, with higher patient satisfaction being associated with less severe constipation.