Clinical pharmacokinetics and pharmacodynamics of solifenacin

Regular and Irregular Use and Reasons for Discontinuation of Solifenacin Therapy in Patients with Overactive Bladder Managed by Urologists

Solifenacin, a selective muscarinic receptor antagonist, is one of the best-tolerated and most effective medicines that relieve storage symptoms in patients with an overactive bladder (OAB). However, the persistence of solifenacin in daily clinical practice remains far below that reported in clinical trials. This study aimed to analyze the adherence of patients to the therapy and the reasons for solifenacin discontinuation and non-regular use in OAB patients managed by urologists. Data concerning non-compliance and the discontinuation of solifenacin, along with the reasons, were collected during two consecutive visits for 64,049 OAB outpatients. Over the two visits, 81.6% of the patients continued therapy, and 88.6% were taking solifenacin regularly. An age ≥ 75 yrs., the male sex, a rural or small-city dwelling, and a prescription of ≥10 mg predicted therapy continuation. The female sex, a higher education, a short or long duration of an OAB, and a non-idiopathic OAB predicted regular use. The persistence of nycturia and urinary incontinence during therapy predicted both discontinuation and non-regular use. Dissatisfaction with therapy was the most frequent reason for discontinuation. In conclusion, an initial prescription of solifenacin at a low dose reduces the chance of OAB symptom improvement and results in more frequent discontinuation. A high rate of discontinuation related to dissatisfaction suggests unrealistic expectations for OAB patients and insufficient education by urologists.

Safety and tolerability of solifenacin in children and adolescents with overactive bladder- a systematic review

BACKGROUND

Solifenacin is an anticholinergic that is used to treat overactive bladder syndrome (OAB) in children. It is important to ascertain the safety and tolerability of solifenacin in the paediatric population as solifenacin offers an alternative, is more bladder specific, and should have less anticholinergic side effects than other therapies.

OBJECTIVE

The aim of this study is to systematically evaluate the safety and tolerability of solifenacin in children and adolescents with OAB.

STUDY DESIGN

We included studies that reported the safety and tolerability of solifenacin in children and adolescents. All study types were included. Electronic searches were conducted in Ovid MEDLINE, Ovid Embase, TRIP, CINAHL and ICTRP on the 18th of January 2022. Risk of bias was assessed with the Cochrane Risk of Bias tool 2.0 (ROB-2) for randomised controlled trials (RCTs) and the Newcastle-Ottowa scale for cohort studies.

RESULTS

A total of twelve studies including two RCTs were included in this review. Results from the meta-analysis of RCTs showed the commonest side effects were constipation (RR 3.5, 95%CI 0.9-13.7) and dry mouth (RR 3.1 95%CI 0.2-53). In terms of tolerability, the effect estimate of ceasing solifenacin due to an adverse effect was 2.7 (95%CI 0.8-9.1). Within the cohort studies, out of the 779 patients 21.7% experienced side effects. The most common side effects were constipation (6.8%) and dry mouth/lips (6.0%) and 3.5% of patients ceased solifenacin due to adverse effects. Overall, the certainty of the evidence for side effects and tolerability were very low.

DISCUSSION

The reported incidence of side effects is low, and less than reported with oxybutynin use. However, the very low certainty of the evidence means the findings should be interpreted with caution. There is limited reporting of a prolonged QTc interval on ECG. Studies that described this only had an increase of QTc from baseline and not a clinically significant prolonged QTc that resulted in arrhythmias.

CONCLUSION

Solifenacin is an alternative anticholinergic for the treatment of OAB in children. However, given the paucity of good quality data on safety and tolerability it should be used cautiously in children with close monitoring for potential side effects.

Analysis of the nervous system and gastrointestinal adverse events associated with solifenacin in older adults using the US FDA adverse event reporting system

BACKGROUND

Antimuscarinics are the backbone of the pharmacological management of overactive bladder. Still, concerns have been raised over the nervous system (NS) adverse drug events (AEs) due to their dissimilarities to muscarinic receptor-subtype affinities.

OBJECTIVE

This study aimed to identify the nervous system and gastrointestinal adverse drug events (ADEs) associated with solifenacin use in older adults (≥65 years).

METHODS

A case/non-case analysis was performed on the reports submitted to the FDA Adverse Event Reporting System (FAERS) between 01/01/2004 and 30/06/2020. Cases were reports for solifenacin with ≥1 ADEs as preferred terms included in the Medical Dictionary of Regulatory Activities (MedDRA) system organ classes 'nervous system' or 'gastrointestinal' disorders. Non-cases were all other remaining reports for solifenacin. The case/non-cases was compared between solifenacin and other bladder antimuscarinics. Frequentist approaches, including the proportional reporting ratio (PRR) and reporting odds ratio (ROR), were used to measure disproportionality. The empirical Bayesian Geometric Mean (EBGM) score and information component (IC) value were calculated using a Bayesian approach. A signal was defined as the lower limit of 95% confidence intervals of ROR ≥ 2, PRR ≥ 2, IC > 0, EBGM > 1, for ADEs with ≥4 reports.

RESULTS

107 MedDRA preferred terms (PTs) comprising 970 ADE reports were retrieved for nervous system disorders associated with solifenacin. For gastrointestinal disorders, 129 MedDRA PTs comprising 1817 ADE reports were retrieved. Statistically significant results were found for 'altered state of consciousness': ROR = 9.71 (2.13-44.35), PRR = 9.69 (2.12-44.2) and IC = 1.29 (0.93-1.66).

CONCLUSIONS

The disproportionality reporting of 'altered state of consciousness', a previously unidentified ADE, was unexpected. Further monitoring of this ADE is needed to ensure patient safety, as this could be linked to poor balance and falls in older adults.

Innovative electrochemical electrode modified with Al2O3 nanoparticle decorated MWCNTs for ultra-trace determination of tamsulosin and solifenacin in human plasma and urine samples and their pharmaceutical dosage form

A simple, cheap, sensitive, and time-saving square wave voltammetric (SWV) procedure using a carbon paste electrode modified with aluminum oxide nanoparticle decorated multi-walled carbon nanoparticles (Al2O3-NPs/MWCNTs/CPE) is presented for the ultra-sensitive determination of tamsulosin (TAM) and solifenacin (SOL), one of the most prescribed pharmaceutical combinations in urology. Characterization of the developed electrode was performed using scanning electron microscopy (SEM), X-ray diffraction (XRD) patterns, energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM) and FT-IR spectrophotometry. The voltammetric behavior of TAM/SOL was evaluated using Al2O3-NPs in different content and electrode compositions. The use of Al2O3 functionalized MWCNTs as a CPE modifier increased the process of electron transfer as well as improved the electrode active surface area therefore, ultra-sensitive results were acquired with a linear range of 10-100 and 12-125 ng ml-1 for TAM and SOL respectively, and a limit of the detection value of 2.69 and 3.25 ng ml-1 for TAM and SOL, respectively. Interestingly, the proposed method succeeded in quantifying TAM and SOL with acceptable percentage recoveries in dosage forms having diverged concentration ranges and in the biological fluids with very low peak plasma concentration (C max). Furthermore, the proposed method was validated, according to the ICH criteria, and shown to be accurate and reproducible.

A Novel In Vitro Membrane Permeability Methodology Using Three-dimensional Caco-2 Tubules in a Microphysiological System Which Better Mimics In Vivo Physiological Conditions

The aim of this study was to develop an in vitro drug permeability methodology which mimics the gastrointestinal environment more accurately than conventional 2D methodologies through a three-dimensional (3D) Caco-2 tubules using a microphysiological system. Such a system offers significant advantages, including accelerated cellular polarization and more accurate mimicry of the in vivo environment. This methodology was confirmed by measuring the permeability of propranolol as a model compound, and subsequently applied to those of solifenacin and bile acids for a comprehensive understanding of permeability for the drug product in the human gastrointestinal tract. To protect the Caco-2 tubules from bile acid toxicity, a mucus layer was applied on the surface of Caco-2 tubules and it enables to use simulated intestinal fluid. The assessment using propranolol reproduced results equivalent to those obtained from conventional methodology, while that using solifenacin indicated fluctuations in the permeability of solifenacin due to various factors, including interaction with bile acids. We therefore suggest that this model will serve as an alternative testing system for measuring drug absorption in an environment closely resembling that of the human gastrointestinal tract.

The Effectiveness in Activating M-Type K+ Current Produced by Solifenacin ([(3R)-1-azabicyclo[2.2.2]octan-3-yl] (1S)-1-phenyl-3,4-dihydro-1H-isoquinoline-2-carboxylate): Independent of Its Antimuscarinic Action

Solifenacin (Vesicare^®, SOL), known to be a member of isoquinolines, is a muscarinic antagonist that has anticholinergic effect, and it has been beneficial in treating urinary incontinence and neurogenic detrusor overactivity. However, the information regarding the effects of SOL on membrane ionic currents is largely uncertain, despite its clinically wide use in patients with those disorders. In this study, the whole-cell current recordings revealed that upon membrane depolarization in pituitary GH₃ cells, the exposure to SOL concentration-dependently increased the amplitude of M-type K⁺ current (I_K(M)) with effective EC₅₀ value of 0.34 μM. The activation time constant of I_K(M) was concurrently shortened in the SOL presence, hence yielding the K_D value of 0.55 μM based on minimal reaction scheme. As cells were exposed to SOL, the steady-state activation curve of I_K(M) was shifted along the voltage axis to the left with no change in the gating charge of the current. Upon an isosceles-triangular ramp pulse, the hysteretic area of I_K(M) was increased by adding SOL. As cells were continually exposed to SOL, further application of acetylcholine (1 μM) failed to modify SOL-stimulated I_K(M); however, subsequent addition of thyrotropin releasing hormone (TRH, 1 μM) was able to counteract SOL-induced increase in I_K(M) amplitude. In cell-attached single-channel current recordings, bath addition of SOL led to an increase in the activity of M-type K⁺ (K_M) channels with no change in the single channel conductance; the mean open time of the channel became lengthened. In whole-cell current-clamp recordings, the SOL application reduced the firing of action potentials (APs) in GH₃ cells; however, either subsequent addition of TRH or linopirdine was able to reverse SOL-mediated decrease in AP firing. In hippocampal mHippoE-14 neurons, the I_K(M) was also stimulated by adding SOL. Altogether, findings from this study disclosed for the first time the effectiveness of SOL in interacting with K_M channels and hence in stimulating I_K(M) in electrically excitable cells, and this noticeable action appears to be independent of its antagonistic activity on the canonical binding to muscarinic receptors expressed in GH₃ or mHippoE-14 cells.

The role of sex, age and genetic polymorphisms of CYP enzymes on the pharmacokinetics of anticholinergic drugs

There is evidence that use of drugs with anticholinergic properties increases the risk of cognitive impairment, and increased exposure to these drugs potentiates this risk. Anticholinergic drugs are commonly used even with associated risk of adverse events. Aging, sex, and genetic polymorphisms of cytochrome P450 (CYP) enzymes are associated with alterations in pharmacokinetic processes, which increase drug exposure and may further increase the risk of adverse drug events. Due to the increasing burden of cognitive impairment in our aging population and the future of personalized medicine, the objective of this review was to provide a critical clinical perspective on age, sex, and CYP genetic polymorphisms and their role in the metabolism and exposure to anticholinergic drugs. Age-related changes that may increase anticholinergic drug exposure include pseudocapillarization of liver sinusoidal endothelial cells, an approximate 3.5% decline in CYP content for each decade of life, and a reduction in kidney function. Sex-related differences that may be influenced by anticholinergic drug exposure include women having delayed gastric and colonic emptying, higher gastric pH, reduced catechol-O-methyl transferase activity, reduced glucuronidation, and reduced renal clearance and men having larger stomachs which may affect medication absorption. The overlay of poor metabolism phenotypes for CYP2D6 and CYP2C19 may further modify anticholinergic drug exposure in a significant proportion of the population. These factors help explain findings of clinical trials that show older adults and specifically older women achieve higher plasma concentrations of anticholinergic drugs and that poor metabolizers of CYP2D6 experience increased drug exposure. Despite this knowledge neither age, sex nor CYP phenotype are routinely considered when making decisions about the use or dosing of anticholinergic medications. Future study of anticholinergic medication needs to account for age, sex and CYP polymorphisms so that we may better approach personalized medicine for optimal outcomes and avoidance of medication-related cognitive impairment.

Different antimuscarinics when combined with atomoxetine have differential effects on obstructive sleep apnea severity

The combination of the noradrenergic agent atomoxetine plus the antimuscarinic oxybutynin has recently been shown to improve upper airway physiology and reduce obstructive sleep apnea (OSA) severity. However, the effects of different antimuscarinics when combined with atomoxetine is limited. This study aimed to determine the effects of atomoxetine combined with two different antimuscarinics with varying M-subtype receptor selectivity on OSA severity and upper airway physiology. Ten people with predominantly severe OSA completed a double-blind, randomized, placebo-controlled, cross-over trial. Participants completed three overnight in-laboratory sleep studies after either 80 mg atomoxetine + 5 mg solifenacin succinate (ato-sol) or 80 mg atomoxetine + 2 mg biperiden hydrochloride (ato-bip) or placebo. OSA severity, ventilatory stability (loop gain), respiratory-arousal threshold (via epiglottic manometry), next-day subjective sleepiness [Karolinska Sleepiness Scale (KSS)], and alertness were compared between conditions. Neither drug combination altered the apnea/hypopnea index versus placebo (P = 0.63). Ato-sol caused a shift toward milder respiratory events with reduced frequency of obstructive apneas (13 ± 14 vs. 22 ± 17 events/h; means ± SD, P = 0.04) and increased hypopneas during nonrapid eye movement (NREM) (38 ± 21 vs. 24 ± 18 events/h, P = 0.006) with improved nadir oxygenation versus placebo (83 ± 4 vs. 80 ± 8%, P = 0.03). Both combinations reduced loop gain by ∼10% versus placebo; sleep efficiency and arousal threshold were unaltered. Ato-bip reduced next-day sleepiness versus placebo (KSS = 4.3 ± 2.2 vs. 5.6 ± 1.6, P = 0.03). Atomoxetine + biperiden hydrochloride reduces perceived sleepiness, and atomoxetine + solifenacin modestly improves upper airway function in people with OSA but to a lesser extent versus recently published atomoxetine + oxybutynin (broad M-subtype receptor selectivity) findings. These results provide novel mechanistic insight into the role of noradrenergic and antimuscarinic agents on sleep and breathing and are important for pharmacotherapy development for OSA.NEW & NOTEWORTHY In contrast to recent findings of major reductions in OSA severity when atomoxetine is combined with a nonspecific antimuscarinic, oxybutynin (broad M-subtype receptor selectivity), addition of solifenacin succinate (M2 and M3 muscarinic receptor selectivity) or biperiden (M1 muscarinic receptor selectivity) with atomoxetine had modest effects on upper airway function during sleep, which provide mechanistic insight into the role of noradrenergic and antimuscarinic agents on sleep and breathing and are important for pharmacotherapy development for OSA.

In Silico Design and Selection of New Tetrahydroisoquinoline-Based CD44 Antagonist Candidates

CD44 promotes metastasis, chemoresistance, and stemness in different types of cancer and is a target for the development of new anti-cancer therapies. All CD44 isoforms share a common N-terminal domain that binds to hyaluronic acid (HA). Herein, we used a computational approach to design new potential CD44 antagonists and evaluate their target-binding ability. By analyzing 30 crystal structures of the HA-binding domain (CD44HAbd), we characterized a subdomain that binds to 1,2,3,4-tetrahydroisoquinoline (THQ)-containing compounds and is adjacent to residues essential for HA interaction. By computational combinatorial chemistry (CCC), we designed 168,190 molecules and compared their conformers to a pharmacophore containing the key features of the crystallographic THQ binding mode. Approximately 0.01% of the compounds matched the pharmacophore and were analyzed by computational docking and molecular dynamics (MD). We identified two compounds, Can125 and Can159, that bound to human CD44HAbd (hCD44HAbd) in explicit-solvent MD simulations and therefore may elicit CD44 blockage. These compounds can be easily synthesized by multicomponent reactions for activity testing and their binding mode, reported here, could be helpful in the design of more potent CD44 antagonists.

Transition Metal-Free Synthesis of Carbamates Using CO2 as the Carbon Source

Utilization of carbon dioxide as a C1 synthon is highly attractive for the synthesis of valuable chemicals. However, activation of CO₂ is highly challenging, owing to its thermodynamic stability and kinetic inertness. With this in mind, several strategies have been developed for the generation of carbon-heteroatom bonds. Among these, formation of C-N bonds is highly attractive, especially, when carbamates can be synthesized directly from CO₂ . This Minireview focuses on transition metal-free approaches for the fixation of CO₂ to generate carbamates for the production of fine chemicals and pharmaceuticals. Within the past decade, transition metal-free approaches have gained increasing attention, but traditional reviews have rarely focused on these approaches. Direct comparisons between such methods have been even more scarce. This Minireview seeks to address this discrepancy.

Improvement of the symptoms of lower urinary tract and sexual dysfunction with tadalafil and solifenacin after the treatment of benign prostatic hyperplasia with dutasteride

Background

The aim of this research is to study the influence of simultaneous taking of tadalafil and solifenacin in standard and double dosage on the lower urinary tract symptoms (LUTS) and sexual dysfunction in men with benign prostatic hyperplasia after the course of dutasteride.

Materials and methods

The research included 326 patients older than 50 years with benign prostatic hyperplasia coupled with LUTS and sexual dysfunction having undergone the course of treatment with dutasteride. After random division into three groups, patients from the Group A (n = 107) got tadalafil 5 mg/d as monotherapy, from the Group В (n = 107) got tadalafil 5 mg/d and solifenacin 10 mg/d, and from the Group С (n = 112) got tadalafil 5 mg/d and solifenacin 20 mg/d. The duration of treatment was 12 weeks. The rating of sexual function was made with the questionnaires International Index of Erectile Function and other.

Results

The results of rating of sexual function with the questionnaires MSHQ-EjD and International Index of Erectile Function correlated among themselves. According to MSHQ-EjD, overall rating of the sexual function increased in each of the three groups (A: 67.9 (12.4)/91.5 (10.4), P ≤ 0.05; B: 72.4 (14.5)/102.6 (16.9), P ≤ 0.05; C: 76.6 (16.3)/109.6 (15.6), P ≤ 0.05). The level of hyperactivity symptoms decreased in Groups В and С (В: urgency −2.9 (0.7)/1.1 (0.6), P ≤ 0.05; nocturia 2.7 (1.0)/0.7 (0.5), P ≤ 0.05; C: urgency −2.5 (0.5)/0.8 (0.6), P ≤ 0.05; nocturia −2.8 (0.6)/1.0 (0.5), P ≤ 0.05), and it did not change in the Group A.

Conclusions

The use of tadalafil as monotherapy significantly improves the sexual function but does not affect overactive bladder symptoms. The combination therapy of tadalafil and solifenacin leads to dramatic improvement of sexual function and reversibility of detrusor hyperactivity symptoms.

A novel HPLC-DAD method for simultaneous determination of alfuzosin and solifenacin along with their official impurities induced via a stress stability study; investigation of their degradation kinetics

Stability and impurity profiling are in high demand to guarantee the potency, safety and efficacy of new formulations along with their shelf-life. In this study, stability testing of alfuzosin (ALF) and solifenacin (SOL) in their newly co-formulated capsules was conducted under different stress conditions. The obtained degradation products were structurally elucidated and found to be their official impurities, namely; ALF impurity-D and SOL impurities-A, E & I. A selective and reliable stability-indicating HPLC method was developed for assaying the cited drugs along with three of those official impurities. Chromatographic separation was accomplished within 8 minutes using a XBridge® C18 column as the stationary phase and acetonitrile : phosphate buffer (pH 8) : triethylamine (60 : 40 : 0.02, by volume) as the mobile phase at a flow rate of 1.3 mL min-1. Quantification of the analytes was performed at 210 nm using a diode array detector through which peak purity was assessed. The proposed method was validated as per ICH guidelines and it was successfully applied for the determination of the cited drugs in their combined pharmaceutical formulation with percent recoveries of 100.47 and 100.15 for ALF and SOL, respectively. Moreover, the proposed method was exploited for the assessment of the two drugs' stability in Solitral® capsules under accelerated storage conditions. The method was further extended for studying the degradation kinetics of the two drugs.

The mechanism of solifenacin release from a pH-responsive ion-complex oral suspension in the fasted upper gastrointestinal lumen

The main objective of this study was to investigate the mechanism of solifenacin release from a pH-responsive ion-complex oral resinate suspension under conditions simulating the environment in the upper gastrointestinal lumen. A secondary objective was to propose an appropriate in vitro methodology for evaluating the quality of orally administered solifenacin suspensions. The mechanism of solifenacin release from polacrilin potassium resin (Amberlite® IRP88) was investigated using biorelevant media and compendial setups (USP Apparatus 2 and USP Apparatus 4) and using newer, recently validated in vitro methodologies [biorelevant gastrointestinal transfer (BioGIT) system]. We evaluated the impact of particle size and concentration of the resin; thickener concentration (carbomer homopolymer, type B); and the impact of pH, cationic strength, agitation intensity and level of simulation of contents in the upper gastrointestinal lumen. Data suggested that solifenacin release from the resinate was determined by the resin particle size, the medium pH, cationic strength (when the conditions in the upper small intestine are simulated) and the level of simulation of contents in the upper small intestine. The interaction of solifenacin with taurocholic acid/lecithin aggregates was significant, but unlikely to affect the degree of solifenacin absorption, as a BCS Class I compound. Under acidic conditions, solifenacin was dissociated and released from the pH-responsive resin rapidly. Under conditions simulating the contents of the upper small intestine, solifenacin was replaced by cations from the testing media and diffused through the resin matrix. All three in vitro systems with or without a pH gradient are useful in distinguishing solifenacin release characteristics from resinate suspensions with different particle sizes. Because of this drug release mechanism, USP Apparatus 2 with fixed pH media demonstrated equivalent or slightly higher discriminative sensitivity than the other setups and appears to be appropriate for product quality control.

Evaluation of in Vitro and in Vivo Transdermal Absorption of Solifenacin Succinate

Solifenacin (Sol), an antimuscarinic agent has been widely used for the treatment of overactive bladder. Transdermal formulations can be administered without water as well as absorbed slowly into the blood over a long period of time. The aim of this study was to develop cream and tape formulations of Sol, and evaluate the transdermal permeation and absorption of the drug from the two formulations in vitro and in vivo, respectively. In the preparation of cream formulation, Sol succinate was dissolved in purified water, and the mixture was added to the hydrophilic cream. Then, aqueous sodium hydroxide was added to the cream. In the tape formulation, Sol succinate was dissolved in a solvent with propylene glycol, diisopropanolamine, triethyl citrate, and EUDRAGIT E100. The dissolved solvent was poured onto a polyethylene film. Cream (5%) and tape (15%) formulations demonstrated high skin permeability. Addition of an adsorption enhancer (N-methyl-2-pyrrolidone) did not further increase the level of skin permeability. In subsequent in vivo experiments in rats, both the cream and tape formulations led to slow absorption of Sol into plasma, with increased t_1/2 compared with oral administration. Plasma Sol concentrations peaked 24 h after transdermal application and the drug was still detectable in plasma 72 h after application. Additionally, the cream (5%) and tape (15%) formulations resulted in a higher area under the plasma concentration vs. time curve from 0 to 72 h (AUC_0-72) compared with oral formulation (30 mg/kg). In conclusion, significant in vitro permeability and in vivo absorption of Sol from the transdermal formulations were observed.

A Pediatric Covariate Function for CYP3A-Mediated Midazolam Clearance Can Scale Clearance of Selected CYP3A Substrates in Children

Recently a framework was presented to assess whether pediatric covariate models for clearance can be extrapolated between drugs sharing elimination pathways, based on extraction ratio, protein binding, and other drug properties. Here we evaluate when a pediatric covariate function for midazolam clearance can be used to scale clearance of other CYP3A substrates. A population PK model including a covariate function for clearance was developed for midazolam in children aged 1–17 years. Commonly used CYP3A substrates were selected and using the framework, it was assessed whether the midazolam covariate function accurately scales their clearance. For eight substrates, reported pediatric clearance values were compared numerically and graphically with clearance values scaled using the midazolam covariate function. For sildenafil, clearance values obtained with population PK modeling based on pediatric concentration-time data were compared with those scaled with the midazolam covariate function. According to the framework, a midazolam covariate function will lead to systemically accurate clearance scaling (absolute prediction error (PE) < 30%) for CYP3A substrates binding to albumin with an extraction ratio between 0.35 and 0.65 when binding < 10% in adults, between 0.05 and 0.55 when binding > 90%, and with an extraction ratio ranging between these values when binding between 10 and 90%. Scaled clearance values for eight commonly used CYP3A substrates were reasonably accurate (PE < 50%). Scaling of sildenafil clearance was accurate (PE < 30%). We defined for which CYP3A substrates a pediatric covariate function for midazolam clearance can accurately scale plasma clearance in children. This scaling approach may be useful for CYP3A substrates with scarce or no available pediatric PK information.

Physiologically Based Pharmacokinetic Modeling Suggests Limited Drug-Drug Interaction for Fesoterodine When Coadministered With Mirabegron

5-Hydroxymethyl tolterodine (5-HMT; the active fesoterodine metabolite) is metabolized via the cytochrome P450 (CYP) 2D6 and CYP3A pathways. Mirabegron is a moderate CYP2D6 inhibitor and weak CYP3A inhibitor. Potential drug-drug interactions (DDIs) following coadministration of these 2 overactive bladder treatments were estimated using physiologically based pharmacokinetic models, developed and verified by comparing predicted and observed pharmacokinetic profiles from clinical studies. Models predicted and verified mirabegron and desipramine (CYP2D6 substrate) and 5-HMT and ketoconazole (strong CYP3A inhibitor) DDIs. Mirabegron model-predicted mean steady-state AUC and C_max were within 11% of clinical observations. The predicted versus observed geometric mean ratio (GMR) of AUC_inf for CYP2D6 substrates desipramine and metoprolol coadministered with mirabegron 100 or 160 mg once daily were 3.47 versus 3.41 and 2.97 versus 3.29, respectively, indicating that the mirabegron model can be used to predict clinical CYP2D6 inhibition. 5-HMT fractional clearance by CYP3A and CYP2D6 was verified from clinical DDI studies with a potent CYP3A4 inhibitor (ketoconazole) and inducer (rifampicin) in CYP2D6 extensive and poor metabolizers and with a moderate CYP3A inhibitor (fluconazole) in healthy volunteers. 5-HMT AUC_inf and C_max GMRs for fesoterodine DDIs were all predicted within 1.26-fold of clinical observation, providing verification for the fesoterodine substrate model. The predicted changes in 5-HMT AUC_inf and C_max ratios for 8 mg fesoterodine when coadministered with 50 mg mirabegron were 1.22-fold and 1.17-fold, respectively, relative to 8 mg fesoterodine given alone. This modest increase in 5-HMT exposures by approximately 20% is considered clinically insignificant and would not require fesoterodine dose adjustment when coadministered with mirabegron within approved daily-dose ranges.

Pharmacokinetics comparison of solifenacin tartrate and solifenacin succinate: a randomized, open-label, single-dose, 2-way crossover study in healthy male volunteers

Solifenacin is a muscarinic antagonist indicated for the treatment of overactive bladder with symptoms. Solifenacin tartrate is a newly developed salt formulation of solifenacin. This study compared the pharmacokinetic and safety properties after single-dose administration of solifenacin tartrate (test formulation) and solifenacin succinate (reference formulation) in healthy male volunteers. A total of 36 subjects were enrolled in this randomized, open-label, single-dose, two-way crossover study. During each treatment period, subjects received the test formulation or reference formulation. Plasma samples were collected at pre-dose and at 1, 2, 3, 4, 5, 6, 7, 8, 10, 12, 24, 48 and 72 hours post-dose. Safety was assessed by adverse events, physical examinations, laboratory assessments, 12-lead electrocardiograms, and vital signs. Thirty-three subjects completed the study and were included in the pharmacokinetic analysis. The mean (standard deviation) values of AUC_last for the test and reference formulations were 486.98 (138.47) and 469.07 (128.29) h·ng/mL, respectively. The mean (standard deviation) values of C_max for the test and reference formulations were 14.66 (3.85) and 14.10 (3.37) ng/mL, respectively. The 90% confidence intervals for AUC_last and C_max were 0.9702 to 1.1097 and 0.9779 to 1.0993, respectively. All adverse events were mild or moderate, and there were no serious adverse events. The pharmacokinetic properties of solifenacin tartrate were similar to those of solifenacin succinate and met the acceptance criteria for bioequivalence. Both formulations were safe, and no significant difference was observed in the safety assessments of the formulations.

Assessment of inhibitory effects on major human cytochrome P450 enzymes by spasmolytics used in the treatment of overactive bladder syndrome

BACKGROUND

The objective of this study was to examine the inhibitory potential of darifenacin, fesoterodine, oxybutynin, propiverine, solifenacin, tolterodine and trospium chloride on the seven major human cytochrome P450 enzymes (CYP) by using a standardized and validated seven-in-one cytochrome P450 cocktail inhibition assay.

METHODS

An in vitro cocktail of seven highly selective probe substrates was incubated with human liver microsomes and varying concentrations of the seven test compounds. The major metabolites of the probe substrates were simultaneously analysed using a validated liquid chromatography tandem mass spectrometry (LC-MS/MS) method. Enzyme kinetics were estimated by determining IC50 and Ki values via nonlinear regression. Obtained Ki values were used for predictions of potential clinical impact of the inhibition using a static mechanistic prediction model.

RESULTS

In this study, 49 IC50 experiments were conducted. In six cases, IC50 values lower than the calculated threshold for drug-drug interactions (DDIs) in the gut wall were observed. In these cases, no increase in inhibition was determined after a 30 min preincubation. Considering a typical dosing regimen and applying the obtained Ki values of 0.72 µM (darifenacin, 15 mg daily) and 7.2 µM [propiverine, 30 mg daily, immediate release (IR)] for the inhibition of CYP2D6 yielded a predicted 1.9-fold and 1.4-fold increase in the area under the curve (AUC) of debrisoquine (CYP2D6 substrate), respectively. Due to the inhibition of the particular intestinal CYP3A4, the obtained Ki values of 14 µM of propiverine (30 mg daily, IR) resulted in a predicted doubling of the AUC for midazolam (CYP3A4 substrate).

CONCLUSIONS

In vitro/in vivo extrapolation based on pharmacokinetic data and the conducted screening experiments yielded similar effects of darifenacin on CYP2D6 and propiverine on CYP3A4 as obtained in separately conducted in vivo DDI studies. As a novel finding, propiverine was identified to potentially inhibit CYP2D6 at clinically occurring concentrations.

Solifenacin/tamsulosin fixed-dose combination therapy to treat lower urinary tract symptoms in patients with benign prostatic hyperplasia

Treatment of male lower urinary tract symptoms (LUTS) has traditionally focused on the management of benign prostatic obstruction, but the contribution of bladder dysfunction has been recently recognized. Therefore, it is well understood that LUTS have multifactorial etiology and often occur in clusters and not in isolation. Voiding LUTS are highly prevalent in men, but storage LUTS have been proved to be more bothersome. α₁-Blockers are the most widely used pharmacologic agents for the treatment of symptoms relating to benign prostatic enlargement due to benign prostatic hyperplasia (BPH), while antimuscarinics are the drug class of choice for overactive bladder symptoms. A combination of the two drug classes would be a reasonable approach to treat men with both storage and voiding symptoms, and several short-term studies have proved the efficacy and safety of different combinations with an α₁-blocker and an antimuscarinic. Following previous studies on the separate administration of solifenacin and tamsulosin, a fixed-dose combination tablet of tamsulosin oral controlled absorption system (OCAS) 0.4 mg and solifenacin succinate 6 mg has been recently introduced, and the current review evaluates the available data on the use of this fixed-dose combination in the treatment of LUTS in men with BPH.

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.

Long-term use of solifenacin in pediatric patients with overactive bladder: Extension of a prospective open-label study

INTRODUCTION

We evaluate the efficacy and safety of solifenacin to treat incontinence in children with non-neurogenic (DO) or neurogenic detrusor overactivity (NDO) refractory to oxybutinin or tolterodine.

METHODS

We updated and extended our previously published non-randomized uncontrolled study on open-label use of adjusted-dose regimens of solifenacin (1.25-10 mg) in children with refractory incontinence. The follow-up included voiding diaries, post-void residuals, urine cultures, ultrasounds and urodynamic studies. Clinical data were updated as of September 2012. Subjective improvement was assessed with the Patient Perception of Bladder Condition (PPBC) scale. The primary end point was efficacy toward continence and secondary end points were tolerability and safety.

RESULTS

Overall, 244 patients (112 girls, 132 boys) were enrolled; 53 with NDO and 191 with DO. Minimal follow-up was 5 months, the mean duration of treatment was 21.0 months and the mean age at initiation was 9.2 years. Urodynamic capacity improved from 145 ± 76 mL to 339 ± 152 mL and the amplitude of uninhibited contractions decreased from 66 ± 26 to 20 ± 20 cmH2O (p < 0.0001). The overall success rate is 91%, and more specifically 94% for non-neurogenic and 79% for neurogenic, which is significantly different (p = 0.013). Twenty-three patients discontinued treatment for unsatisfactory clinical response or bothersome side effects. No side effects were reported by 175 patients, mild by 46, moderate by 9, and 14 withdrew due to their side effects. Ten patients developed post-void residuals of ≥20 mL.

CONCLUSION

Although higher in the non-neurogenic group, high subjective and objective success rates were maintained over a longer follow-up with an adjusted-dose regimen of solifenacin to treat pediatric NDO or DO refractory to oxybutynin or tolterodine. Moreover, we found acceptable tolerability and safety profiles.

Therapeutic benefit in patients switching tolterodine to other novel antimuscarinic agents

OBJECTIVES

To explore in the daily clinical practice setting that antimuscarinic, Fesoterodine or Solifenacin, provides a greater clinical benefit after changing their prior Overactive Bladder (OAB) therapy with tolterodine extended-release (ER) to other novel antimuscarinic agents.

MATERIAL AND METHODS

A post-hoc analysis of data from an observational multicenter, cross-sectional, retrospective study. Adult patients of both sexes, with OAB and OAB-V8 score≥8, who switched to fesoterodine or solifenacin within the 3-4 months before study visit from their prior tolterodine-ER-based therapy due to poor response were included. 92 patients were selected for each treatment group, matched (1:1) according to conditioned probability using the propensity score. Benefit of treatment change perceived by the physician and patient was evaluated by means of the Clinical Global Impression of Improvement subscale (CGI-I) and Treatment Benefit Scale (TBS), respectively. Degree of worry, bother and interference with daily living activities due to urinary symptoms, level of satisfaction, and preference for current treatment were also assessed.

RESULTS

Fesoterodine provided a significantly greater improvement than solifenacina in terms of therapeutic benefit perceived by the physician according to ICG-I. 96.7% of the patients on fesoterodine treatment vs. 81.6% of the solifenacin group showed a score of improvement in TBS (P<.05). Fesoterodine was also better rated than solifenacin with regard to satisfaction and preference for the new treatment (93.4 vs. 78.2% P<.05).

CONCLUSIONS

In daily clinical practice the switch from tolterodine LP to fesoterodine seems to provide greater benefits both from the physician's and the patient's point of view compared with those provided by solifenacin.

Solifenacin-induced delirium and hallucinations

Solifenacin-induced cognitive adverse effects have not been reported frequently, but solifenacin-induced delirium and hallucinations with successful switching to darifenacin, without additional drug, have not been reported in the literature. In this case report, we present an 80-year-old Caucasian male with insomnia and anxiety symptoms and overactive bladder who developed delirium and hallucinations when treated with solifenacin and trazodone. After solifenacin discontinuation and switching to darifenacin, symptoms significantly improved immediately. Such a case has not yet been described in literature; however, an adverse effect associated with solifenacin can occur, as this report clearly demonstrates.

Pharmacokinetics and toxicity of antimuscarinic drugs for overactive bladder treatment in females

INTRODUCTION

Antimuscarinics (AMs) are the mainstay of pharmacological treatment of overactive bladder (OAB), a symptom complex defined by the presence of urinary urgency, usually associated with frequency and nocturia, with or without urgency urinary incontinence. The AMs used to treat OAB differ in their pharmacological profiles, which may affect their potential for causing adverse effects (AEs).

AREAS COVERED

The present article aims to review the literature about pharmacokinetics (PK) of the different AMs used in the treatment of OAB. Furthermore, the AEs related to the use of these drugs and their incidence are presented. This systematic review is based on material searched and obtained via Medline, Pubmed and EMBASE up to March 2012 using the search terms "adverse events, pharmacokinetics, tolerability" in combination with "darifenacin, fesoterodine, imidafenacin, oxybutynin, propiverine, solifenacin, tolterodine, and trospium."

EXPERT OPINION

Antimuscarinics are the first-line pharmacological treatment for OAB. Despite the development of new molecules that improve their efficacy/safety profile, there are some drugs that are pharmacokinetically more appropriate to be prescribed in specific populations such as patients with neurological disease or the elderly. Moreover, research should be encouraged in evaluating antimuscarinics in conjunction with other drugs such as estrogens or beta-agonists. The identification of prognostic criteria for pharmacological therapy would be helpful.

Overactive Bladder Syndrome: The Social and Economic Perspective

Overactive bladder syndrome (OAB) is a highly prevalent condition associated with a significant impairment of patients’ Quality of Life (QoL) because of its adverse effects on social, sexual, interpersonal, and professional functions. Cost-of-illness analyses showed the huge economic burden related to OAB for patients, public healthcare systems, and society, secondary to both direct and indirect costs. These types of cost analyses, however, exclude intangible costs related to QoL impairment. Recently, many novel therapies have been introduced, arising the need to apply the modern methodology of Health Technology Assessment (HTA) to new therapies in order to evaluate objectively their value in terms of both improvement in length/Quality of Life and costs. By producing information on the clinical, economic, organizational, social and ethical impact of health technologies, HTA has been used worldwide to inform decision makers at different levels in health systems. The HTA approach demonstrated, worldwide, to be a useful approach to increase the level of appropriateness in the use of medical technology and, as a consequence of that, of resources. Health utilities are instruments that allow a measurement of QoL and its integration in the economic evaluation using the Quality-of-life-Adjusted-Life-Years (QALYs) model and cost-utility analysis. The development of suitable instruments for quantifying utility in the specific group of OAB patients is vitally important to extend the application of cost-utility analysis in OAB and to guide healthcare resources allocation for this disorder. Studies are required to define the cost-effectiveness of available pharmacological and non-pharmacological therapy options.

Nocturia and aging: diagnosis and treatment

Nocturia is a frequently encountered problem in clinical practice and a reason for nephrology consultation. Many studies have clearly shown the negative effect of nocturia on several aspects of health-related quality of life and morbidity. Age-associated physiological, structural, hormonal, and histological changes play an important role in the increasing incidence of nocturia in elderly individuals. Besides urologic conditions, nocturia may also be the initial presenting symptom in chronic kidney disease, as well as other systemic diseases. Therefore, it is essential to understand the complex pathophysiology among these factors to establish a precise diagnosis and appropriate management strategies. This review will provide an overview of the effect of aging on the kidneys and urinary system, the pathophysiology, clinical assessment, and treatment strategies of nocturia, and its effect on health-related quality of life.