The Pharmacokinetics, Safety and Tolerability of Aclidinium Bromide 400 μg Administered by Inhalation as Single and Multiple (Twice Daily) Doses in Healthy Chinese Participants

Purpose

To date, aclidinium pharmacokinetic (PK) studies have focused on Caucasian populations, and no data are available for Chinese populations. We aimed to characterize the PK and safety profile of aclidinium and its metabolites (LAS34823 and LAS34850) following single and multiple (twice-daily; BID) dosing in healthy Chinese participants, and to compare PK data between Chinese and Caucasian populations.

Materials and methods

In this Phase I, open-label study (NCT03276052), healthy participants from a single site in China received aclidinium bromide 400 µg via a dry powder inhaler. The Day 1 single dose was followed by a washout period of 96 hours. On Days 5 through 8, participants received BID doses.

Results

Twenty healthy Chinese participants, aged 18-45 years, were enrolled. Aclidinium absorption was rapid (median time to maximum concentration [tmax] 0.08 hours post-dose following single/multiple doses). LAS34823 had a similar median tmax of 0.08 hours, whereas LAS34850 tmax occurred later (median 2.50-3.00 hours). Aclidinium, LAS34823, and LAS34850 concentrations declined in a bi-phasic manner; geometric mean half-life was 13.5 hours (single dosing) and 21.4 hours (multiple dosing), while steady state was generally achieved after 5 days' continuous dosing. Area under the concentration-time curve during a dosage interval (AUCτ) metabolite to parent ratios for LAS34823 were 2.6 (Day 1) and 2.9 (Day 9), while LAS34850 had ratios of 136.0 and 94.8, respectively. Aclidinium accumulation occurred after 5 days of BID dosing (LS mean accumulation ratio for AUCτ Day 9/Day 1: 214.1% [90% CI, 176.5, 259.6]); LAS34823 accumulation was similar, while LAS34850 accumulation was lower. Between-participant exposure variability was moderate to high for aclidinium and LAS34823, and low for LAS34850.

Conclusion

Single and multiple doses of aclidinium were well tolerated in healthy Chinese participants. The safety profile of and exposure to aclidinium was consistent with previous studies conducted in Caucasian populations.

Biperiden Challenge Model in Healthy Elderly as Proof-of-Pharmacology Tool: A Randomized, Placebo-Controlled Trial

Selective M1 muscarinic acetylcholine receptor (mAChR) agonists are being developed as symptomatic treatment for neurodegenerative and neuropsychiatric disorders that lead to cognitive dysfunction. Demonstrating cognition-enhancing effects in early-phase clinical development in healthy subjects is difficult. A challenge with the M1 mAChR antagonist biperiden could be used to demonstrate procognitive and pharmacological effects of selective M1 mAChR agonists. The aim of this study was to develop such a model. To this end, 12 healthy elderly subjects participated in a randomized, placebo-controlled, 3-way crossover study investigating tolerability, pharmacokinetic (PK) and pharmacodynamic (PD) effects of 2 and 4 mg biperiden. Repeated PD assessments were performed using neurocognitive tasks and electrophysiological measurements. A population PK-PD model was developed. Four milligrams of biperiden showed significant impairment of sustained attention (-2.1 percentage point in adaptive tracking [95%CI, -3.043 to -1.148], verbal memory (2-3 fewer words recalled [95%CI, -5.9 to -0.2]) and working memory (up to a 50-millisecond increase in the n-back task reaction time [95%CI, 21.854-77.882]) compared with placebo. The PK data were best fitted by a 2-compartment model and showed high interoccasion and intersubject variability. Population PK-PD analysis quantified significant concentration-effect relationships for the n-back reaction time, n-back accuracy, and adaptive tracking. In conclusion, biperiden caused M1 mAChR-related dose- and concentration-dependent temporary declines in cognitive functioning. Therefore a biperiden pharmacological challenge model can be used for proof-of-pharmacology studies and to demonstrate cognition-enhancing effects of new cholinergic compounds that are being developed.

Trospium Chloride Transport by Mouse Drug Carriers of the Slc22 and Slc47 Families

Background: The muscarinic receptor antagonist trospium chloride (TCl) is used for pharmacotherapy of the overactive bladder syndrome. TCl is a hydrophilic positively charged drug. Therefore, it has low permeability through biomembranes and requires drug transporters for distribution and excretion. In humans, the organic cation transporters OCT1 and OCT2 and the multidrug and toxin extrusion MATE1 and MATE2-K carriers showed TCl transport. However, their individual role for distribution and excretion of TCl is unclear. Knockout mouse models lacking mOct1/mOct2 or mMate1 might help to clarify their role for the overall pharmacokinetics of TCl. Method: In preparation of such experiments, TCl transport was analyzed in HEK293 cells stably transfected with the mouse carriers mOct1, mOct2, mMate1, and mMate2, respectively. Results: Mouse mOct1, mOct2, and mMate1 showed significant TCl transport with Km values of 58.7, 78.5, and 29.3 µM, respectively. In contrast, mMate2 did not transport TCl but showed MPP⁺ transport with Km of 60.0 µM that was inhibited by the drugs topotecan, acyclovir, and levofloxacin. Conclusion: TCl transport behavior as well as expression pattern were quite similar for the mouse carriers mOct1, mOct2, and mMate1 compared to their human counterparts.

Pharmacokinetics of solifenacin in pediatric populations with overactive bladder or neurogenic detrusor overactivity

The aim of this investigation was to characterize and compare the pharmacokinetics (PK) of the antimuscarinic drug solifenacin in pediatric patients with overactive bladder (OAB) or neurogenic detrusor overactivity (NDO) utilizing data from three phase III trials. LION was a placebo-controlled, 12-week trial in children (5-<12 years) and adolescents (12-<18 years) with OAB. MONKEY and MARMOSET were open-label, 52-week trials in children and adolescents or younger children (6 months-<5 years), respectively, with NDO. During the trials, solifenacin doses could be titrated to weight-adjusted pediatric equivalent doses (PEDs) of 2.5, 5, 7.5, or 10 mg day-1 . Nonlinear mixed effects modeling was used to develop population PK models to characterize the PK in patients with either OAB or NDO. Overall, 194 children and adolescents received solifenacin. At the time of PK sampling, the majority (119/164 [72.6%] patients) were receiving PED10 once daily. All population models included first-order oral absorption, a lag time, and interindividual variability. PK analysis showed that apparent clearance was similar in both patient populations. Mean apparent oral plasma clearance (CL/F), apparent volume of distribution during the terminal phase (Vz /F), and terminal half-life (t1/2 ) were higher in adolescents than in children, but median time to maximum plasma concentration (tmax ) was similar. Dose-normalized exposure results were similar for both younger and older patients with OAB or NDO. In conclusion, population PK modeling was used to successfully characterize solifenacin PK in pediatric patients with OAB or NDO. Similar solifenacin PK characteristics were observed in both populations.

Pharmacokinetics and efficacy of atropine sulfate/obidoxime chloride co-formulation against VX in a guinea pig model

Nerve agent exposure is generally treated by an antidote formulation composed of a muscarinic antagonist, atropine sulfate (ATR), and a reactivator of acetylcholinesterase (AChE) such as pralidoxime, obidoxime (OBI), methoxime, trimedoxime or HI-6 and an anticonvulsant. Organophosphates (OPs) irreversibly inhibit AChE, the enzyme responsible for termination of acetylcholine signal transduction. Inhibition of AChE leads to overstimulation of the central and peripheral nervous system with convulsive seizures, respiratory distress and death as result. The present study evaluated the efficacy and pharmacokinetics (PK) of ATR/OBI following exposure to two different VX dose levels. The PK of ATR and OBI administered either as a single drug, combined treatment but separately injected, or administered as the ATR/OBI co-formulation, was determined in plasma of naïve guinea pigs and found to be similar for all formulations. Following subcutaneous VX exposure, ATR/OBI-treated animals showed significant improvement in survival rate and progression of clinical signs compared to untreated animals. Moreover, AChE activity after VX exposure in both blood and brain tissue was significantly higher in ATR/OBI-treated animals compared to vehicle-treated control. In conclusion, ATR/OBI has been proven to be efficacious against exposure to VX and there were no PK interactions between ATR and OBI when administered as a co-formulation.

Evidence-based review of data on the combination inhaler umeclidinium/vilanterol in patients with COPD

The use of inhaled, fixed-dose, long-acting muscarinic antagonists (LAMA) combined with long-acting, beta2-adrenergic receptor agonists (LABA) has become a mainstay in the maintenance treatment of chronic obstructive pulmonary disease (COPD). One of the fixed-dose LAMA/LABA combinations is the dry powder inhaler (DPI) of umeclidinium bromide (UMEC) and vilanterol trifenatate (VI) (62.5 µg/25 µg) approved for once-a-day maintenance treatment of COPD. This paper reviews the use of fixed-dose combination LAMA/LABA agents focusing on the UMEC/VI DPI inhaler in the maintenance treatment of COPD. The fixed-dose combination LAMA/LABA inhaler offers a step beyond a single inhaled maintenance agent but is still a single device for the COPD patient having frequent COPD exacerbations and persistent symptoms not well controlled on one agent. Currently available clinical trials suggest that the once-a-day DPI of UMEC/VI is well-tolerated, safe and non-inferior or better than other currently available inhaled fixed-dose LAMA/LABA combinations for COPD.

Revefenacin: First Global Approval

Revefenacin (YUPELRI™) inhalation solution, a long-acting muscarinic antagonist (i.e. an anticholinergic) developed by Theravance Biopharma and Mylan, is the first and currently the only once-daily, nebulized bronchodilator to be approved in the USA for the treatment of chronic obstructive pulmonary disease (COPD). In November 2018, based on results of three phase III trials, the US Food and Drug Administration granted market authorization to revefenacin for the maintenance treatment of patients with COPD. This article summarizes the milestones in the development of revefenacin leading to this first global approval.

Inhaled glycopyrrolate for the treatment of chronic obstructive pulmonary disease

Long-acting muscarinic antagonists (LAMAs), along with long-acting β2-agonists (LABAs), are the mainstay for treatment of patients with COPD. Glycopyrrolate, or glycopyrronium bromide, like other LAMAs, inhibits parasympathetic nerve impulses by selectively blocking the binding of acetylcholine to muscarinic receptors. Glycopyrrolate is unusual in that it preferentially binds to M3 over M2 muscarinic receptors, thereby specifically targeting the primary muscarinic receptor responsible for bronchoconstriction occurring in COPD. Inhaled glycopyrrolate is slowly absorbed from the lungs and rapidly eliminated from the bloodstream, most likely by renal excretion in its unmetabolized form, limiting the potential for systemic adverse events. Inhaled glycopyrrolate is a fast-acting, efficacious treatment option for patients with moderate-severe COPD. It improves lung function, reduces the risk of exacerbations, and alleviates the symptoms of breathlessness, which in turn may explain the improvement seen in patients' quality of life. Inhaled formulations containing glycopyrrolate are well tolerated, and despite being an anticholinergic, few cardiovascular-related events have been reported. Inhaled glycopyrrolate is thus of value as both monotherapy and in combination with other classes of medication for maintenance treatment of COPD. This review covers the mechanism of action of inhaled glycopyrrolate, including its pharmacokinetic, pharmacodynamic, and safety profiles, and effects on mucus secretion. It also discusses the use of inhaled glycopyrrolate in the treatment of COPD, as monotherapy and in fixed-dose combinations with LABAs and inhaled corticosteroid-LABAs, including a triple therapy recently approved in Europe.

Discovery and optimization of 3-(4-aryl/heteroarylsulfonyl)piperazin-1-yl)-6-(piperidin-1-yl)pyridazines as novel, CNS penetrant pan-muscarinic antagonists

This letter describes the synthesis and structure activity relationship (SAR) studies of structurally novel M4 antagonists, based on a 3-(4-aryl/heteroarylsulfonyl)piperazin-1-yl)-6-(piperidin-1-yl)pyridazine core, identified from a high-throughput screening campaign. A multi-dimensional optimization effort enhanced potency at human M4 (hM4 IC50s<200nM), with only moderate species differences noted, and with enantioselective inhibition. Moreover, CNS penetration proved attractive for this series (rat brain:plasma Kp=2.1, Kp,uu=1.1). Despite the absence of the prototypical mAChR antagonist basic or quaternary amine moiety, this series displayed pan-muscarinic antagonist activity across M1-5 (with 9- to 16-fold functional selectivity at best). This series further expands the chemical diversity of mAChR antagonists.

Continued optimization of the M5 NAM ML375: Discovery of VU6008667, an M5 NAM with high CNS penetration and a desired short half-life in rat for addiction studies

This letter describes the continued optimization of M₅ NAM ML375 (VU0483253). While a valuable in vivo tool compound, ML375has an excessively long elimination half-life in rat (t_1/2=80h), which can be problematic in certain rodent addiction paradigms (e.g., reinstatement). Thus, we required an M₅ NAM of comparable potency to ML375, but with a rat t_1/2 of less than 4h. Steep SAR plagued this chemotype, and here we detail aniline replacements that offered some improvements over ML375, but failed to advance. Ultimately, incorporation of a single methyl group to the 9b-phenyl ring acted as a metabolic shunt, providing (S)-11 (VU6008667), an equipotent M₅ NAM, with high CNS penetration, excellent selectivity versus M_1-4 and the desired short half-life (t_1/2=2.3h) in rat.

Pharmacokinetics of sternal intraossesous atropine administration in normovolemic and hypovolemic swine

OBJECTIVE

Characterize and compare the pharmacokinetics of atropine administered via the sternal intraosseous (IO) route in a normovolemic and hypovolemic swine model.

DESIGN

Prospective, experimental study.

SETTING

Vivarium.

SUBJECTS

Yorkshire-cross swine (N = 12).

INTERVENTION

Atropine was administered via the sternal IO route to normovolemic and hypovolemic swine. Blood samples were drawn at regular intervals after atropine administration and analyzed for plasma atropine concentration. Pharmacokinetic parameters were obtained from modeling the plasma concentrations.

MAIN OUTCOME MEASUREMENTS

Pharmacokinetic parameters, maximum concentration (Cmax), and time to maximum concentration (Tmax).

RESULTS

The normovolemic and hypovolemic models reached peak plasma concentration immediately and had a very rapid distribution phase with no apparent absorption phase for the IO groups. The hypovolemic group had slower clearance and longer half-life compared to the normovolemic group.

CONCLUSION

The sternal IO route is an effective method of administering atropine and is comparable to the previously reported tibial IO and intravenous data even under conditions of significant hemorrhage.

Discovery, synthesis and characterization of a highly muscarinic acetylcholine receptor (mAChR)-selective M5-orthosteric antagonist, VU0488130 (ML381): a novel molecular probe

Of the five G-protein-coupled muscarinic acetylcholine receptors (mAChRs; M1-M5), M5 is the least explored and understood due to a lack of mAChR subtype-selective ligands. We recently performed a high-throughput functional screen and identified a number of weak antagonist hits that are selective for the M5 receptor. Here, we report an iterative parallel synthesis and detailed molecular pharmacologic profiling effort that led to the discovery of the first highly selective, central nervous system (CNS)-penetrant M5-orthosteric antagonist, with sub-micromolar potency (hM5 IC50=450 nM, hM5 Ki=340 nM, M1-M4 IC50>30 μM), enantiospecific inhibition, and an acceptable drug metabolism and pharmacokinetics (DMPK) profile for in vitro and electrophysiology studies. This compound will be a powerful tool and molecular probe for the further investigation into the role of M5 in addiction and other diseases.

Randomized study of the safety, pharmacokinetics, and bronchodilatory efficacy of a proprietary glycopyrronium metered-dose inhaler in study patients with chronic obstructive pulmonary disease

BACKGROUND

Bronchodilator medications are central to the symptomatic management of chronic obstructive pulmonary disease (COPD). Metered-dose inhalers (MDIs) are the most commonly used devices to deliver treatment to patients with COPD and asthma, comprising approximately 70% of bronchodilator prescriptions. Proprietary porous-particle technology permits the formulation of long-acting muscarinic antagonists, long-acting β2-agonists, and a combination of both in hydrofluoroalkane (HFA) MDIs, providing a solution to formulation challenges inherent to the development of HFA MDIs, which have contributed to the development of dry-powder inhalers.

METHODS

In this randomized, double-blind, 4-period, 6-treatment, placebo- and active-controlled, multicenter, crossover study, 4 ascending single doses of a proprietary glycopyrronium (GP) MDI were evaluated compared with Placebo MDI and open-label tiotropium (TIO) in study patients with COPD. Thirty-three study patients were enrolled and received single-dose administration of 4 of the 6 treatments (Placebo MDI, TIO 18 μg, or GP MDI at 14.4, 28.8, 57.6, and 115.2 μg ex-actuator) with an interval of 1 to 3 weeks between doses. The primary efficacy endpoint was peak change in forced expiratory volume in 1 second (FEV1).

RESULTS

All 4 doses of GP MDI showed statistically superior efficacy compared with Placebo MDI for peak FEV1 (differences of 146 to 248 mL; P<.001), with a clear dose ordering of the response. Statistically significant differences compared with Placebo MDI were noted at almost all doses for the secondary FEV1 parameters (P ≤ .049) except 24-hour trough FEV1 at 28.8 μg. All doses were safe and well tolerated in this study; the most frequently reported adverse event was dry mouth (0-14.3% across doses; 9.5% for Placebo MDI, and 9.1% for TIO).

CONCLUSIONS

This study demonstrated superior bronchodilatory efficacy of GP MDI compared with Placebo MDI at all doses tested, and no serious adverse events were reported. This study supports the further evaluation of GP MDI in study patients with COPD. In addition, these findings indicate that the correct dosage of glycopyrronium is no more than 115.2 μg total daily dose, or 57.6 μg twice daily based on comparisons with the active comparator.

TRIAL REGISTRATION

This clinical trial was registered on ClinicalTrials.gov, Identifier: NCT00871182.

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.

Determination of the pharmacokinetics of glycopyrronium in the lung using a population pharmacokinetic modelling approach

AIMS

Glycopyrronium bromide (NVA237) is a once-daily long-acting muscarinic antagonist recently approved for the treatment of chronic obstructive pulmonary disease. In this study, we used population pharmacokinetic (PK) modelling to provide insights into the impact of the lung PK of glycopyrronium on its systemic PK profile and, in turn, to understand the impact of lung bioavailability and residence time on the choice of dosage regimen.

METHODS

We developed and validated a population PK model to characterize the lung absorption of glycopyrronium using plasma PK data derived from studies in which this drug was administered by different routes to healthy volunteers. The model was also used to carry out simulations of once-daily and twice-daily regimens and to characterize amounts of glycopyrronium in systemic compartments and lungs.

RESULTS

The model-derived PK parameters were comparable to those obtained with noncompartmental analysis, confirming the usefulness of our model. The model suggested that the lung absorption of glycopyrronium was dominated by slow-phase absorption with a half-life of about 3.5 days, which accounted for 79% of drug absorbed through the lungs into the bloodstream, from where glycopyrronium was quickly eliminated. Simulations of once-daily and twice-daily administration generated similar PK profiles in the lung compartments.

CONCLUSIONS

The slow absorption from the lungs, together with the rapid elimination from the systemic circulation, could explain how once-daily glycopyrronium provides sustained bronchodilatation with a low incidence of adverse effects in patients with chronic obstructive pulmonary disease. Its extended intrapulmonary residence time also provides pharmacokinetic evidence that glycopyrronium has the profile of a once-daily drug.

Predictive Power of an In Vitro System to Assess Drug Interactions of an Antimuscarinic Medication: A Comparison of In Vitro and In Vivo Drug-Drug Interaction Studies of Trospium Chloride With Digoxin

The authors studied a potential drug-drug interaction via findings from in vitro and in vivo studies, to assess whether the in vitro system was predictive of in vivo clinical pharmacokinetic outcomes. An in vitro experiment and a clinical study were performed to assess the potential for interaction. The effect of trospium chloride on human P-glycoprotein-mediated transport of [3H]-digoxin was determined in vitro. A randomized, crossover clinical trial in 40 subjects was performed to evaluate the effect of trospium on the pharmacokinetics of digoxin in vivo. The findings from the studies were then compared. The in vitro findings in this study were corroborated by the clinical study via assessment of inhibition and impact on pharmacokinetic parameters. The in vitro system for assessment of a potential interaction of 2 drugs excreted primarily through the kidney was predictive of the pharmacokinetic outcomes obtained from a clinical setting.

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.

Safety, tolerability, pharmacodynamics and pharmacokinetics of umeclidinium and vilanterol alone and in combination: a randomized crossover trial

Umeclidinium bromide (GSK573719; UMEC), a new long-acting muscarinic receptor antagonist (LAMA), is in development with vilanterol (GW642444; VI), a selective long-acting β₂ agonist (LABA), as a once-daily inhaled combination therapy for the treatment of chronic obstructive pulmonary disease (COPD). A single dose healthy volunteer study was conducted to assess the safety and tolerability, pharmacodynamics (PD) and pharmacokinetics (PK) of inhaled umeclidinium (500 µg) and vilanterol (50 µg) when administered separately and in combination using a novel dry powder inhaler (NDPI). Co-administration of single inhaled doses of umeclidinium and vilanterol to healthy Japanese subjects was well tolerated and not associated with meaningful changes in systemic exposure or PD effects compared with administration of either compound individually. Pharmacokinetic assessments showed rapid absorption for both drugs (Tmax = 5 min for both umeclidinium and vilanterol) followed by rapid elimination with median tlast of 4–5 h for umeclidinium and median tlast of 1.5–2.0 h for vilanterol. Assessments of pharmacokinetic interaction were inconclusive since for umeclidinium, Cmax following combination was higher than umeclidinium alone but not AUC whereas for vilanterol, AUC following combination was higher than vilanterol alone but not Cmax. There were no obvious trends observed between individual maximum supine heart rate and umeclidinium Cmax or vilanterol Cmax when delivered as umeclidinium 500 µg and vilanterol 50 µg combination or when delivered as umeclidinium or vilanterol alone.

Profile of glycopyrronium for once-daily treatment of moderate-to-severe COPD

Bronchodilators are central in the symptomatic management of chronic obstructive pulmonary disease (COPD). Long-acting muscarinic antagonists (LAMAs) and long-acting β(2)-agonists (LABAs) are the main classes of long-acting bronchodilators. To date, tiotropium is the only once-daily LAMA available for the treatment of COPD. Glycopyrronium is a novel LAMA, currently in development for COPD. Phase II studies have shown that glycopyrronium 50 μg once daily provides clinically significant 24-hour bronchodilation with a rapid onset of action, which is faster than that of tiotropium, and a favorable safety and tolerability profile. The Phase III GLycopyrronium bromide in COPD airWays (GLOW) program has now confirmed the long-term efficacy and tolerability of glycopyrronium 50 μg once daily. The three studies included in this program have further shown that the effect of glycopyrronium versus placebo is similar to that of tiotropium in reducing dyspnea and the risk of exacerbations, as well as improving lung function, exercise tolerance, and health status in patients with COPD. The safety profile of glycopyrronium is also similar to that of tiotropium in terms of overall incidence of adverse events and muscarinic side effects. Glycopyrronium could be an alternative choice to tiotropium, and like tiotropium, has the potential to be used as a monotherapy or combination therapy. Phase II studies have shown that a fixed-dose combination of glycopyrronium and the 24-hour LABA indacaterol, produces rapid and sustained bronchodilation compared with indacaterol monotherapy in patients with COPD. Phase III studies are currently ongoing to assess the long-term efficacy and safety of this combination.

Glycopyrrolate for chronic drooling in children

BACKGROUND

Sialorrhea, or drooling, is seen in the pediatric population, especially in patients with cerebral palsy and other neurodevelopmental disabilities. If medication use is warranted, anticholinergic agents are the drug of choice; however, adverse effects limit their use. Glycopyrrolate, a synthetic anticholinergic that acts at peripheral muscarinic receptors, has been used off-label for excessive drooling in children with neurodevelopmental disabilities for years. Product formulations restricted the use of glycopyrrolate. However, an oral solution was approved by the US Food and Drug Administration for children ages 3 to 16 years with neurologic disorders for chronic severe drooling in 2010; it became available for use in 2011.

OBJECTIVE

This article provides an overview of the pharmacology, clinical efficacy, and tolerability of glycopyrrolate when used for sialorrhea in children.

METHODS

To evaluate the efficacy and safety profile of glycopyrrolate for the treatment of sialorrhea in children, a comprehensive search was performed of the MEDLINE database (1966-February 25, 2012) and International Pharmaceutical Abstracts as well as references from additional review articles identified. Searches were conducted using the terms glycopyrrolate, sialorrhea, drooling, secretion, and pediatrics. The terms drug-induced and Parkinson disease-associated sialorrhea were excluded from the search. The pharmaceutical manufacturer of the oral solution was contacted for medical and study information.

RESULTS

Oral bioavailability of glycopyrrolate varies widely, with a median of 3.3%. Mean C(max) in children was determined to be 0.37 μg/mL, and mean T(max) was 3.1 hours. The clearance in children ranges from 0.6 to 1.43 L/kg/h. The t(½) ranges from 22 to 130 minutes and 19 to 99 minutes in infants and children, respectively. Six studies describing the use of glycopyrrolate for drooling in children were identified. A double-blind, crossover trial of 27 patients (age range, 4-19 years) demonstrated a reduced mean drooling score (modified Teacher's Drooling Scale [1 = never drools to 9 = clothing, hands, and objects frequently become wet]) for glycopyrrolate (mean highest tolerated dose, 0.11 mg/kg) compared with placebo of 1.85 versus 6.33 (P < 0.001). In a parallel study of 36 patients (age range, 3-16 years), 14 of 20 patients randomized to receive glycopyrrolate solution showed improvement in the mean modified Teacher's Drooling Scale score compared with only 3 patients receiving placebo (-3.5 vs -0.1, respectively). Glycopyrrolate was initiated at 0.02 mg/kg per dose orally TID (Max dose: 3 mg) and titrated over a 4-week period. Adverse effects identified in studies include dry mouth (9%-41%), constipation (9%-39%), and behavioral changes (18%-36%).

CONCLUSIONS

Glycopyrrolate is effective in decreasing sialorrhea in children with cerebral palsy or other neurodevelopmental disabilities. Adverse effects did occur, more frequently at higher doses, and should be monitored.

The Genuair® inhaler: a novel, multidose dry powder inhaler

This article reviews the Genuair(®) inhaler, a novel, multidose, breath-actuated dry powder inhaler. The inhaler design includes visual and acoustic feedback to reassure patients that they have taken their medication correctly, a dose indicator and a lock-out mechanism to prevent the use of an empty inhaler. The inhaler has medium airflow resistance and uses an optimised dispersion system to ensure effective deagglomeration of the inhalation powder. In vitro studies have demonstrated that the inhaler delivers a reproducible aerodynamic aerosol quality and is reliable under various thermal and mechanical stress conditions. Further studies in vitro have demonstrated that the total emitted dose and fine particle dose are both consistent over a range of inhalation flows from 45 to 95 l/min, as well as being independent of inhalation volume (2 l vs. 4 l) and storage conditions. In healthy subjects, delivery of aclidinium bromide 200 μg via the inhaler achieved high lung deposition (approximately 30% of the metered dose). A further study has shown that patients with moderate or severe chronic obstructive pulmonary disease can generate sufficient inspiratory airflow through the inhaler to reliably inhale the full dose and reset the inhaler. The inhaler has been used to deliver aclidinium in many clinical trials and the available data indicate that it has high acceptability amongst patients.

Profile of aclidinium bromide in the treatment of chronic obstructive pulmonary disease

Bronchodilators provide the mainstay of pharmacologic therapy for chronic obstructive pulmonary disease (COPD), and anticholinergic bronchodilators, in particular, appear to be the most effective. There are currently two anticholinergic agents available in the US for the treatment of COPD (ipratropium bromide and tiotropium bromide), but several others are in various stages of development. Aclidinium bromide, a novel, long-acting, anticholinergic bronchodilator, is currently in Phase III trials for the management of COPD. Available evidence suggests that aclidinium is a safe and well tolerated drug with a relatively rapid onset and a sufficient duration of action to provide once-daily dosing. This article will provide a pharmacologic profile of aclidinium bromide and review the preclinical and clinical studies evaluating its safety and efficacy in the treatment of COPD.

[Pharmacokinetics of scopolamine hydrobromide oral disintegrative microencapsule tablets in Beagle dogs determined with LC-MS/MS]

The study aims to elucidate the characteristics of pharmacokinetics of scopolamine hydrobromide oral disintegrative microencapsule tablets in healthy Beagle dogs. Chromatographic separation was performed on a C18 column (100 mm x 3.0 mm, 3.5 microm) with methanol - 2 mmol x L(-1) ammonium formate (25 : 75) as the mobile phase. A trip-quadrupole tandem mass spectrum with the electrospray ionization (ESI) source was applied and positive ion multiple reaction monitoring mode was operated. Six Beagle dogs were randomly devided into two groups. They received oral single dose of scopolamine hydrobromide oral disintegrative microencapsule tablets 0.6 mg (test tablet) or scopolamine hydrobromide normal tablets (reference tablet). Plasma samples were collected at designed time. Plasma concentration of scopolamine hydrobromide was determined by LC-MS/MS and pharmacokinetic parameters were calculated. The pharmacokinetic parameters of test tablet vs reference tablet were as follows: C(max): (8.16 +/- 0.67) ng x mL(-1) vs (3.54 +/- 0.64) ng x mL(-1); t1/2: (2.83 +/- 0.45) h vs (3.85 +/- 0.82) h; t(max): (1.25 +/- 0.27) h vs (0.42 +/- 0.09) h; AUC(0-12h): (25.06 +/- 3.75) h x ng x mL(-1) vs (9.59 +/- 1.02) h x ng x mL(-1); AUC(0-infinity): (26.30 +/- 3.92) h x ng x mL(-1) vs (10.80 +/- 1.45) h x ng x mL(-1); MRT(0-12h): (3.38 +/- 0.34) h vs (3.86 +/- 0.26) h; MRT(0-infinity): (3.98 +/- 0.63) h vs (5.37 +/- 1.00) h. The absorption rate and AUC of test tablet is different from that of reference tablet. The bioavailability of test tablet is better than those of reference tablet.

Trospium chloride has no effect on memory testing and is assay undetectable in the central nervous system of older patients with overactive bladder

BACKGROUND

Muscarinic receptors in the brain play an important role in cognitive function, especially memory, and there is growing awareness that specific antimuscarinic drugs for overactive bladder (OAB) may have adverse central nervous system (CNS) effects. Selection of an antimuscarinic OAB drug with reduced potential for CNS effects could be especially beneficial in the elderly people, in whom even the modest cognitive impairment may negatively affect independence.

PURPOSE

The purpose of the study is to determine if trospium chloride is assay detectable in the CNS of older adults with OAB and to assess whether deterioration of memory occurs in these individuals.

METHODS

Twelve cognitively intact older adults (>or=65-75 years old) with OAB were given extended-release trospium chloride 60 mg once daily over a 10-day period to achieve plasma steady-state levels. Standardised memory testing (Hopkins Verbal Learning Test-Revised and Brief Visuospatial Memory Test-Revised) was performed predose and postdose. Cerebrospinal spinal fluid (CSF) and plasma samples were drawn on day 10 and assayed for trospium chloride. Predose (day 0) and postdose (day 10) results on the memory tests were compared using a reliable change index to assess a meaningful change in learning or memory.

RESULTS

Trospium chloride levels in all the CSF samples (n = 72) of all participants were assay undetectable (<40 pg/ml) on day 10 at steady-state peak plasma concentration concurrent with measureable peak plasma values (C(max) = 925 pg/ml). Repeat memory testing revealed no significant net drug effect on learning or recall.

CONCLUSIONS

This is the first study to investigate for the presence of an OAB antimuscarinic in the human brain, performed by assaying for concentrations of trospium chloride and correlating with simultaneous clinical cognitive safety measures. The results of both pharmacological and neuropsychological testing support the hypothesis of a lack of detectable CNS penetration for the quaternary amine trospium chloride.

Review of cognitive impairment with antimuscarinic agents in elderly patients with overactive bladder

Overactive bladder (OAB) will become an increasingly prevalent problem as the proportion of older people in the population increases over the next 20 years. In addition to the urological symptoms (urinary urgency, with or without urgency incontinence, usually with increased daytime frequency and nocturia), OAB is associated with other problems in older patients, especially an increased risk of falls and fractures. The bother caused by OAB needs not be an inevitable consequence of ageing, because the symptoms can usually be alleviated, even in frail older people. Pharmacological treatment for OAB involves the use of antimuscarinic agents, whose efficacy and safety profiles depend on their interactions with muscarinic receptors that are widely distributed throughout the body. Interactions between antimuscarinics and M(1) receptors in the central nervous system may have the potential to cause cognitive impairment in older people, depending on muscarinic receptor binding profiles, lipophilicity and the ability to cross the blood brain barrier. Concerns over the possibility of cognitive impairment have contributed to an under-utilisation of antimuscarinics in the geriatric population, despite the high prevalence and severity of OAB in older subjects. Antimuscarinic agents should be actively considered for elderly patients with OAB, but it is desirable to establish the cognitive risk for every type of antimuscarinic, using robust cognition assessment methods.

Solifenacin pharmacology

Antimuscarinics are the drugs of choice for the treatment of overactive bladder syndrome, and their benefit/risk ratio depends largely on selectivity for the different subtypes of muscarinic receptors. Solifenacin is the antimuscarinic that presents greatest selectivity for M3 bladder receptors, which may translate into a lower incidence of undesirable effects related to other receptor subtypes. Metabolic pathways of the antimuscarinics may impact efficacy and appearance of interactions. Solifenacin is metabolized only by the CYP3A4, giving three inactive metabolites and one with a similar activity to the original compound. However, other drugs in the group are also a substrate for the CYP 2D6 which presents polymorphisms, whereby their pharmacokinetics may be modified in slow metabolizers. The risk of interactions of solifenacin is low, and it is lower than that of the antimuscarinics which are also metabolized by the CYP 2D6. The unaltered fraction of solifenacin which is eliminated in urine, together with the active metabolite, can contribute to the therapeutic effect by acting on the urothelium receptors. It is not necessary to adjust doses of solifenacin in elderly patients or those with moderate liver or kidney impairment.

Preserving cognitive function for patients with overactive bladder: evidence for a differential effect with darifenacin

BACKGROUND

Antimuscarinic agents used in the treatment of overactive bladder (OAB) differ in their potential to impair cognitive function. It is hypothesised that low brain concentrations and relatively low selectivity for the M(1) muscarinic receptor may reduce the potential for adverse central nervous system (CNS) effects with darifenacin, compared with other antimuscarinics, particularly oxybutynin.

METHODS

Cognitive function studies evaluating darifenacin, oxybutynin, tolterodine, solifenacin and/or trospium were identified from publications databases (Medline, Biosis and Embase) and congress abstracts. Preclinical studies and randomised controlled trials in adults were reviewed.

RESULTS

Five randomised, double-blind, multiple-dose studies of cognitive function were identified. Oxybutynin was consistently associated with cognitive deficit (four studies), whereas darifenacin did not impair cognition (three studies). These findings were supported by data from sleep/attention and EEG studies. Tolterodine data were limited to one small study with each formulation. For solifenacin and trospium, there were no human studies evaluating memory, the cognitive function most vulnerable to CNS anticholinergics.

CONCLUSIONS

There is compelling evidence of cognitive impairment with oxybutynin, whereas darifenacin stands out by demonstrating no impairment of memory or other cognitive functions in three randomised, controlled trials. This may be attributed to the differences in physicochemical properties, efflux mechanisms and relative M(1) muscarinic receptor sparing. The risk of CNS impairment is of particular concern for vulnerable populations such as the elderly (a substantial proportion of the OAB population), and CNS-compromised neurogenic bladder patients such as those with multiple sclerosis or Parkinson's disease.

Evolution of transdermal oxybutynin in the treatment of overactive bladder

Overactive bladder (OAB) syndrome affects millions of people worldwide. In addition to adversely affecting quality of life, the direct and indirect costs in managing patients with OAB incur a substantial financial burden on health services. Among the approved anticholinergics for treating OAB, oxybutynin is the most extensively studied drug in clinical trials. The principle metabolite of oxybutynin has a higher affinity for muscarinic receptors in salivary glands which lead to significantly high dry mouth rates. This prompted the development of alternative formulations of oxybutynin aiming to achieve better tolerability whilst sustaining efficacy. This editorial examines the efficacy and tolerability of transdermal oxybutynin (OXY-TD) in treating OAB. Articles were retrieved from PubMed between 2000 to the present day relating to OXY-TD. Data is presented from phase I-IV trials. The results from placebo-controlled trials indicate that OXY-TD is efficacious in treating patients with OAB associated with urge urinary or mixed incontinence. Systemic side effects most notably dry mouth, appear to be less with this formulation compared with oral anticholinergics. However, further study is required in different OAB populations. The main limitation appears to be related to application site adverse events such as pruritus and erythema. OXY-TD is likely to find its place as first-line pharmacotherapy in the clinicians' armamentarium in treating OAB.

Formulation study of oxybutynin patches

The present feasibility study was designed to obtain a monolayer patch containing oxybutynin (OXY) avoiding chemical permeation enhancers. The highest flux was obtained with a polydimethylsiloxane matrix patch. Because OXY crystals were detected in the matrix within a week, two amino methylmethacrylate copolymers (Eudragit E or Eudragit RS) were used as OXY crystallization inhibitors. A preliminary in vivo study indicated that flux from the stabilized patches had to be increased about 30-40%. This goal was reached by occlusion with a polyethylene layer.

The effects of external heating on the permeation of oxybutynin through human epidermal membrane

The transdermal delivery system (TDS) of oxybutynin (OXY) is widely used for the treatment of overactive bladder patients. This report aimed to assess the effect of external heating on the pharmacokinetics of OXY after transdermal administration. Franz-type diffusion cell experiments at room temperature, 36 and 45 degrees C were performed to estimate the permeations of OXY through human epidermal membrane with an isosorbide dinitrate (ISDN) formulation as a reference. The fluxes of OXY at 36 and 45 degrees C were only approximately 1.2-fold higher than that at room temperature, while those of ISDN with heating were more than 2.5 times as high as that without heating (p<0.001). These results indicate that the influence of heating on the permeation of OXY from the TDS of OXY may be minimal.

Scopolamine sublingual spray: an alternative route of delivery for the treatment of motion sickness

The purpose of this study was to develop a sublingual drug delivery spray formulation of scopolamine hydrobromide (L-(-)-hyoscine hydrobromide) and to determine the absolute bioavailability of scopolamine hydrobromide following sublingual delivery and to investigate the effect of a bioadhesive on the pharmacokinetic parameters of this drug in a rabbit model. Rabbits received a single scopolamine free base equivalent sublingual dose of 100 microg/kg and this was compared to intravenous administration of the drug. Blood samples were collected at different time points, and plasma scopolamine concentrations were determined using a new sensitive and specific LC/MS analytical method which utilized electrospray ionization detection. The bioavailability of sublingual scopolamine was determined by comparing plasma concentrations after sublingual spray delivery with equivalent intravenous doses. Following delivery of the sublingual spray dose, the average Cmax was 1024.4+/-177 ng/mL, and the AUC value was found to be 61067.6+/-9605 ng.min/mL. Relative to the intravenous dose (100% bioavailability), the bioavailability was 79.8% after sublingual spray administration. The addition of 2% chitosan, a bio-adhesive material and an absorption enhancer, showed a significant improvement in scopolamine sublingual absorption (p<0.05) was observed. Considering the limitations of delivering scopolamine orally or transdermally to patients who experience motion sickness, the sublingual route of administration using a spray delivery dosage form, is a potential alternative modality for the prevention of nausea and vomiting associated with motion sickness.

Opposing short- and long-term effects on muscarinic M1/4 receptor binding following chronic phencyclidine treatment

Phencyclidine (PCP) is a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist. Several studies have demonstrated that chronic NMDA receptor antagonist treatment in humans and animals can cause long-term behavioral changes that are reminiscent of negative and cognitive schizophrenia-like symptoms. The muscarinic cholinergic system, which is associated with cognitive functions, has been hypothesized to contribute to PCP's mechanism of action. No study, however, has examined the status of M1/4 receptors in the PCP model of schizophrenia. The aim of the present study was to investigate the effects of chronic (14 day) PCP treatment on mouse brain M1/4 receptors in the short term (1 hr and 24 hr) and long term (14 days) after last PCP administration. [(3)H]pirenzepine was used to target M1/4 receptors. In the short term following chronic PCP treatment, M1/4 binding was significantly increased in regions of the limbic system, caudate-putamen, cortex, and thalamus (ranging from 56% to 368%), compared with saline-treated mice. There were no differences in binding between mice treated with PCP for 14 days and sacrificed 1 hr or 24 hr after the final PCP treatment. In the long term following chronic PCP treatment, M1/4 binding was significantly decreased in all of the above-mentioned brain regions (ranging from 31% to 72%), except in the thalamus, which showed no change. These findings in the long-term group are similar to those reported in post-mortem studies of patients suffering from schizophrenia.

Absorption, Metabolism, and Excretion of [14C]Imidafenacin, a New Compound for Treatment of Overactive Bladder, After Oral Administration to Healthy Male Subjects

The absorption, metabolism, and excretion of imidafenacin [KRP-197/ONO-8025, 4-(2-methyl-1H-imidazol-1-yl)-2,2-diphenylbutanamide], a new antimuscarinic drug developed for treatment of overactive bladder, were assessed in six healthy male subjects after a single oral administration of 0.25 mg of [(14)C]imidafenacin (approximately 46 microCi). The highest radioactivity in the plasma was observed at 1.5 h after administration. The apparent terminal elimination half-life of the total radioactivity was 72 h. Approximately 65.6 and 29.4% of the administered radioactivity were recovered in the urine and feces, respectively, within 192 h after administration. The metabolite profiling by high-performance liquid chromatography-radiodetector and liquid chromatography/tandem mass spectrometry demonstrated that the main component of radioactivity was unchanged imidafenacin in the 2-h plasma. The N-glucuronide conjugate (M-9) was found as the major metabolite and the oxidized form of the 2-methylimidazole moiety (M-2) and the ring-cleavage form (M-4) were detected as the minor metabolites in the 2-h plasma, but M-4 was found to be the main component in the 12-h plasma. Unchanged imidafenacin, M-9, M-2, and other oxidized metabolites were excreted in the urine, but the unchanged imidafenacin and M-9 were not found in the feces. Two unique metabolites were found in the urine and feces, which were identified as the interchangeable cis- and trans-isomers of 4,5-dihydrodiol forms of the 2-methylimidazole moiety. These findings indicate that imidafenacin is rapidly and well absorbed (at least 65% of dose recovered in urine) after oral administration, circulates in human plasma as the unchanged form, its glucuronide, and other metabolites, and is then excreted in urine and feces as the oxidized metabolites of 2-methylimidazole moiety.

Sodium valproate at therapeutic concentrations changes Ca2+ response accompanied with its weak inhibition of protein kinase C in human astrocytoma cells

Sodium valproate (VPA) has been used clinically for treatment of not only epilepsy but also mood disorder. Although VPA is effective for treatment of epilepsy via inhibition of gamma-aminobutyric acid transaminase, it remains unknown why VPA is effective for the treatment of mood disorder. The authors examined the effect of VPA at therapeutic concentrations (300 and 600 microM) on the elevation of intracellular free calcium concentration ([Ca(2+)](i)) induced by carbachol, a muscarinic receptor agonist, in 1321N1 human astrocytoma cells. Treatment of the cells with 300 and 600 microM VPA for 2 min did not change the carbachol-induced [Ca(2+)](i) elevation. Treatment with 300 and 600 microM VPA for 48 h, however, reduced the elevation. Since we have shown that Li(+) reduced carbachol-induced [Ca(2+)](i) elevation in protein kinase C (PKC)-downregulated 1321N1 cells [Kurita, M., Mashiko, H., Rai, M., Kumasaka, T., Kouno, S., Niwa, S., Nakahata, N., 2002. Lithium chloride at a therapeutic concentration reduces Ca(2+)response in protein kinase C down-regulated human astrocytoma cells, Eur. J. Pharmacol. 442, 17-22.], the activity of PKC was examined. Treatment with VPA at the same concentrations for 24 or 48 h weakly reduced protein kinase C activity in membrane and cytosol fractions from the cells. On the other hand, the treatment of the cells with 600 microM VPA for 24 or 48 h slightly increased the B(max) value, but not the K(d) value, in the binding of [(3)H]quinuclidinyl benzylate, a muscarinic receptor ligand, to the membranes, suggesting that the number or affinity of muscarinic receptor did not decrease after VPA treatment. These results indicate that VPA at therapeutic concentrations slightly decreases the PKC activity and inhibits muscarinic receptor-mediated [Ca(2+)](i) elevation probably through change in the intracellular signaling pathway. VPA-induced reduction of PKC activity and [Ca(2+)](i) elevation may play a role in the treatment of mood disorder.

Serum anticholinergic activity and motor performance in elderly persons

BACKGROUND

Medications prescribed to elderly persons often have an anticholinergic effect, as do many commonly used over-the-counter drugs. Anticholinergic medications are known to produce psychomotor slowing, especially in older persons.

METHODS

The present study examined whether the cumulative anticholinergic load present in the serum of community volunteers was associated with decrements on tests of psychomotor performance (gait speed and simple manual response time) known to predict falls in elderly persons.

RESULTS

Serum anticholinergic activity (SAA) was relatively low in this group; however, an elevated SAA was associated with a significant slowing in both gait speed and simple response time.

CONCLUSION

Cumulative anticholinergic burden may be one of the factors contributing to an increased risk of falls in the older population.

Pharmacokinetics, safety, and tolerability of solifenacin in patients with renal insufficiency

To evaluate the pharmacokinetics, safety, and tolerability of solifenacin in patients with mild, moderate, or severe renal disease, eighteen patients with renal disease and six healthy volunteers received a single oral dose of solifenacin (10 mg). Pharmacokinetic parameters were assessed from blood samples drawn over a 360-h period. Safety and tolerability were also evaluated. Total mean +/- S.D. exposure (ng . h/mL) to solifenacin in healthy individuals (1190 +/- 403) was increased in patients with renal disease (mild: 1784 +/- 792, moderate: 1559 +/- 555, severe: 2530 +/- 700), and elimination half-life (mean +/- S.D. [h]) was prolonged (healthy: 68.2 +/- 27.2, mild: 89.1 +/- 34.5, moderate: 90.6 +/- 27.3, severe: 111 +/- 38.3). A significant correlation was found between creatinine clearance and pharmacokinetic parameters for exposure and apparent oral clearance. No deaths or serious adverse events occurred during the study. Solifenacin 10 mg was well tolerated in patients with renal disease. Solifenacin displays a higher exposure and a prolonged half-life in patients with renal impairment, especially severe. Therefore, while no special cautions are necessary for patients with mild/moderate renal impairment, patients with severe renal impairment should receive no more than 5 mg solifenacin once daily.

Comparative evaluation of central muscarinic receptor binding activity by oxybutynin, tolterodine and darifenacin used to treat overactive bladder

PURPOSE

We characterized muscarinic receptor binding in the mouse cerebral cortex after oral administration of anticholinergic agents used to treat overactive bladder.

MATERIALS AND METHODS

Muscarinic receptors in the mouse cerebral cortex and bladder after oral administration of anticholinergic agents were measured using [(3)H]N-methylscopolamine.

RESULTS

In vitro binding affinities of tolterodine and its metabolite 5-hydroxymethyl metabolite in the mouse cerebral cortex and bladder were considerably greater than those of oxybutynin and darifenacin. Also, muscarinic receptor binding affinity of oxybutynin and its metabolite N-desethyl-oxybutynin in the cerebral cortex compared with that in the bladder was 2 to 3 times higher, whereas that of tolterodine and 5-hydroxymethyl metabolite was approximately 2 times lower. Oral administration of oxybutynin (76.1 micromol/kg), tolterodine (6.31 micromol/kg) and darifenacin (59.1 micromol/kg) showed binding activity that was approximately equal to that of bladder muscarinic receptors. Oral administration of oxybutynin (76.1 micromol/kg) showed significant binding of cerebral cortical muscarinic receptors in mice, as indicated by about a 2-fold increase in K(d) values for specific [(3)H]N-methylscopolamine binding 0.5 and 2 hours later. On the other hand, tolterodine and darifenacin given at oral doses that would exert a similar extent of bladder receptor binding activity as oxybutynin showed only a low level of binding activity of central muscarinic receptors in mice.

CONCLUSIONS

Significant binding of brain muscarinic receptors in mice was observed by the oral administration of oxybutynin but not tolterodine and darifenacin.

Parasympathetic dysfunction is associated with baroreflex and chemoreflex impairment in streptozotocin-induced diabetes in rats

This study explored physiological mechanisms of diabetic dysfunction in baroreceptors and chemoreceptors-mediated hemodynamic responses, and cholinergic neurotransmission in 30-day diabetic rats (n = 14) and controls (n = 14). Basal hemodynamic data and vagal response to electrical stimulation and methacholine injection were also evaluated. Muscarinic receptors were characterized using a radioligand receptor binding assay ([3H]N methylscopolamine). Experimental diabetes (50 mg/kg of STZ, i.v.) decreased systolic, diastolic, and mean arterial pressure and basal heart rate. Heart rate (HR) responses to vagal electrical stimulation (16, 32, and 64 Hz) were 15%, 11%, and 14% higher in diabetics vs non-diabetics, as were HR responses to methacholine injection (-130+/-24, -172+/-18, -206+/-15 bpm vs. -48+/-15, -116+/-12, -151+/-18 bpm, P < 0.05). Muscarinic receptor density was higher (267.4+/-11 vs 193.5+/-22 fmol/mg/prot, P < 0.05) in the atria of diabetic rats than in those of controls; the affinity was similar between groups. Diabetes-induced reduction of reflex responses to baro- (reflex bradycardia: -3.4+/-0.3 and -2.7+/-0.2 bpm/mm Hg; reflex tachycardia: -1.6+/-0.1 and -1.4+/-0.07 bpm/mm Hg, in control and diabetics, P < 0.05) and chemoreceptor stimulation, enhancement of HR responsiveness to cardiac vagal electrical stimulation and methacholine stimulation, plus an increase in the number of atrial muscarinic receptors indicates reduced parasympathetic activity, which is probably derived from central nervous system derangement.

Muscarinic receptors in the bladder: from basic research to therapeutics

Muscarinic receptor antagonists (antimuscarinics) serve as the cornerstone in the pharmacological management of overactive bladder (OAB) by relieving the symptoms of urgency, frequency and incontinence. These drugs operate primarily by antagonizing post-junctional excitatory muscarinic receptors (M(2)/M(3)) in the detrusor. The combination of pharmacological and gene knockout studies has greatly advanced our understanding of the functional role of muscarinic receptors in the bladder. M(3) receptors produce direct smooth muscle contraction by a mechanism that relies on entry of extracellular calcium through L-type channels and activation of a rho kinase. M(2) receptors, which predominate in number, appear to facilitate M(3)-mediated contractions. M(2) receptors can also produce bladder contractions indirectly by reversing cAMP-dependent beta-adrenoceptor-mediated relaxation, although the physiological role of beta-adrenoceptors in detrusor relaxation is controversial. Emerging evidence suggests that muscarinic receptors in the urothelium/suburothelium can modulate the release of certain factors, which in turn may affect bladder function at the efferent or afferent axis. Currently, oxybutynin, tolterodine, darifenacin, solifenacin and trospium are the five major antimuscarinics approved for the treatment of OAB. Comparative clinical studies have shown that oxybutynin and solifenacin may be marginally more effective than tolterodine, although the latter seems to be better tolerated. Pharmacokinetic-pharmacodynamic analyses using plasma concentrations of 'total drug' indicate that, at therapeutic doses, the clinical efficacy of darifenacin and solifenacin may be driven primarily by selective M(3) receptor occupation, whereas the pharmacodynamic effects of pan-selective molecules (such as tolterodine, trospium) may potentially involve multiple receptors, including M(2) and M(3). Furthermore, high M(3) receptor occupation is the likely explanation for the greater propensity of darifenacin and oxybutynin to cause dry mouth and/or constipation. Although the recently introduced drugs represent a significant improvement over older drugs, especially with respect to the convenience of dosing schedule, their overall efficacy and tolerability profile is still less than optimal and patient persistence with therapy is low. Recent advances in basic research have not yet offered a clear discovery path for improving the therapeutic index of antimuscarinic molecules. There is still an unmet need for an antimuscarinic medicine with superior clinical effectiveness that can translate into better persistence on therapy.

Pharmacological assessment of the duration of action of glycopyrrolate vs tiotropium and ipratropium in guinea-pig and human airways

1. Our study was aimed at investigating the duration of the bronchodilator action of the antimuscarinc drug glycopyrrolate compared to tiotropium and ipratropium. In the guinea-pig isolated trachea, the time (t1/2) necessary for a contractile response to carbachol (0.3 microM) to return to 50% recovery after washout of the antagonist was studied. The offset of the antagonist effect of glycopyrrolate, tiotropium and ipratropium (10 nM each) was t1/2 = 4.0 +/- 0.5, > 4.5 and 0.5 +/- 0.1 h, respectively. At 4.5 h from the washout of the antagonist, the recovery of the response to carbachol was 50 +/- 8, 10 +/- 4 and 70 +/- 7%, respectively. 2. In the human isolated bronchus, the offset of the bronchodilator effects of glycopyrrolate (3 nM), tiotropium (1 nM) and ipratropium (10 nM) was t1/2 = 3.7 +/- 0.2; > 6 and 3.0 +/- 0.2 h, respectively. At 6.0 h from the washout of the antagonist, the recovery of the response to carbachol (1 microM) was 101 +/- 10, 27 +/- 3 and 110 +/- 10%, respectively. 4. In anaesthetized guinea-pigs, acetylcholine-induced bronchoconstriction was markedly reduced by intratracheal instillation of glycopyrrolate (3 nmol kg(-1); 88.1 +/- 4% inhibition), tiotropium (1.3 nmol kg(-1); 86.2 +/- 5% inhibition) or ipratropium (1.45 nmol kg(-1); 88.1 +/- 10% inhibition). These inhibitory effects assessed 3 or 24 h after antagonist administration were reduced to 69.9 +/- 5 and 29.7 +/- 6%; 28.3 +/- 5 and 14.2 +/- 5% for glycopyrrolate and ipratropium, respectively, whereas they remained stable (83.5 +/- 4; 70.6 +/- 6) for tiotropium. The residual inhibitory effect of glycopyrrolate was also assessed at 16 h from administration, and proved to be as low as that found at 24 h (31.2 +/- 10 vs 29.7 +/- 6%, respectively). 5. In conclusion, glycopyrrolate-induced bronchodilation has a longer duration than that of ipratropium, but less than that of tiotropium. The efficacy of a possible glycopyrrolate-based therapy for asthma or chronic obstructive pulmonary disease given once-a-day is not guaranteed by the present investigation.

Solifenacin provides effective antimuscarinic therapy for the complete management of overactive bladder

Solifenacin is an antimuscarinic agent, administered once daily, which has been newly approved for the treatment of overactive bladder (OAB). Solifenacin administered at 5- and 10-mg once-daily doses shows efficacy for all the symptoms of OAB in both 'wet' and 'dry' patients, including improvements in patient quality of life and satisfaction. These improvements are observed as early as week 2 of treatment and are maintained over 12-week and 1-year time periods, without being compromised by the age or gender of the patient. Solifenacin demonstrates a favourable tolerability profile, with mild dry mouth as the most common adverse event associated with its use, both at the 5- and 10-mg doses; this allows for flexibility in the dosing regimen, in which physicians can administer solifenacin 5 mg, with the option to safely increase the dose to 10 mg if necessary based on the severity of patient's symptoms. The favourable efficacy and safety profile of solifenacin, coupled with its dose flexibility, are consistent with solifenacin being a convenient treatment option for patients with OAB.

Transdermal scopolamine for prevention of motion sickness : clinical pharmacokinetics and therapeutic applications

A transdermal therapeutic system for scopolamine (TTS-S) was developed to counter the adverse effects and short duration of action that has restricted the usefulness of scopolamine when administered orally or parenterally. The plaster contains a reservoir of 1.5 mg of scopolamine programmed to deliver 0.5 mg over a 3-day period. A priming dose (140 microg) is incorporated into the adhesive layer to saturate certain binding sites within the skin and to accelerate the achievement of steady-state blood levels. The remainder is released at a constant rate of approximately 5 microg/hour. The protective plasma concentration of scopolamine is estimated to be 50 pg/mL. TTS-S attains that concentration after 6 hours; a steady state of about 100 pg/mL is achieved 8-12 hours after application. Yet 20-30% of subjects failed to attain the estimated protective concentration, and plasma concentrations measured in subjects who failed to respond to TTS-S were lower than in responders. These findings may explain some of the treatment failures. Overall, the product appears to be the approximate functional equivalent of a 72-hour slow intravenous infusion. A combination of transdermal and oral scopolamine (0.3 or 0.6 mg) was effective and well tolerated in producing desired plasma concentrations 1-hour post-treatment. TTS-S has proved to be significantly superior to placebo in reducing the incidence and severity of motion sickness by 60-80%. It was more effective than oral meclizine or cinnarizine, similar to oral scopolamine 0.6 mg or promethazine plus ephedrine, and the same as or superior to dimenhydrinate. The addition of ephedrine or the use of two patches did not improve its efficacy, but rather increased the rate of adverse effects. TTS-S was most effective against motion sickness 8-12 hours after application. Despite previous evidence to the contrary, a recent bioavailability study demonstrated similar intraindividual absorption and sustained clinical efficacy with long-term use of the drug. The adverse effects produced by TTS-S, although less frequent, are qualitatively typical of those reported for the oral and parenteral formulations of this agent. Dry mouth occurs in about 50-60% of subjects, drowsiness in up to 20%, and allergic contact dermatitis in 10%. Transient impairment of ocular accommodation has also been observed, in some cases possibly the result of finger-to-eye contamination. Low-dose pyridostigmine was found effective in preventing cycloplegia but not mydriasis. Adverse CNS effects, including toxic psychosis (mainly in elderly and paediatric patients), have been reported only occasionally, as have difficulty in urinating, headache, rashes and erythema. Adverse effects were not correlated with plasma scopolamine concentrations. TTS-S produced only about half the incidence of drowsiness caused by oral dimenhydrinate or cinnarizine, and a level of adverse effects similar to that found with oral meclizine. Performance is not affected by short-term use. Prolonged or repeated application may cause some impairment of memory storage for new information. However, sea studies revealed significantly less reports of a decrement in performance or drowsiness due to prevention of sea sickness. The recommended dosage is a single TTS-S patch applied to the postauricular area at least 6-8 hours before the anti-motion sickness effect is required. For faster protection, the patch may be applied 1 hour before the journey in combination with oral scopolamine (0.3 or 0.6 mg). After 72 hours, the patch should be removed and a new one applied behind the opposite ear. Its place in therapy is mainly on long journeys (6-12 hours or longer), to avoid repeated oral doses, or when oral therapy is ineffective or intolerable.

The clinical pharmacokinetics of darifenacin

Darifenacin hydrobromide is a selective muscarinic M(3) receptor antagonist that is indicated for use in treatment of overactive bladder disorder. Darifenacin was found to have a short terminal elimination half-life after intravenous and immediate-release oral dosage forms (3-4 hours) but this increased with a prolonged-release (PR) formulation (14-16 hours). The absolute bioavailability of darifenacin from 7.5 and 15 mg PR tablets was estimated to be 15.4% and 18.6%, respectively. With repeated once-daily oral administration of the PR formulation, peak plasma concentrations of darifenacin are achieved approximately 7 hours post-dose. After oral administration, darifenacin is well absorbed from the gastrointestinal tract and very little unchanged drug (<2%) is recovered in the faeces. Steady state is achieved after 6 days of once-daily administration of the PR formulation. As expected, values of peak plasma concentration (C(max)) and area under the plasma concentration-time curve are dose dependent, although the increase in plasma concentrations is proportionally greater than the increase in dose owing to saturation of presystemic metabolism. From intravenous administration, it has been established that darifenacin possesses a moderate-to-high hepatic extraction ratio, with high plasma clearance (36-52 L/h) and a volume of distribution (165-276L) that exceeds total body water. It is highly protein bound (98%), primarily to alpha(1)-acid glycoprotein. Darifenacin is subject to extensive hepatic metabolism, with 3% of unchanged drug excreted in urine and faeces. Metabolism is mediated by hepatic cytochrome P450 2D6 and 3A4, the main metabolic routes being monohydroxylation in the dihydrobenzfuran ring, dihydrobenzfuran ring opening, and N-dealkylation of the pyrrolidine nitrogen. Several possibly important drug-drug interactions have been identified with darifenacin, including ketoconazole, erythromycin and fluconazole, each of which increases darifenacin mean C(max) by 9.52-, 2.28- and 1.88-fold, respectively. When given with imipramine, darifenacin causes 1.6-fold higher plasma concentrations of the antidepressant and its major metabolite. Moderate hepatic impairment, but not renal insufficiency, has been shown to increase plasma concentrations of the drug. The pharmacokinetic profile of darifenacin is not affected by food.

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.

Effect of the proton pump inhibitor omeprazole on the pharmacokinetics of extended-release formulations of oxybutynin and tolterodine

This study assessed the effect of the proton pump inhibitor omeprazole on the bioavailability of the extended-release formulations of oxybutynin and tolterodine. Forty-four healthy volunteers received each of 4 treatments in a 4-period crossover design. The treatments consisted of osmotically controlled extended-release oxybutynin chloride tablets at 10 mg/d or extended-release tolterodine tartrate capsules at 4 mg/d, with and without preceding treatment with 20 mg omeprazole daily for 4 days. Blood samples collected predose and at scheduled time points for 36 hours postdose were analyzed for oxybutynin and its active metabolite, N-desethyloxybutynin, or tolterodine and its active 5-hydroxymethyl metabolite, as appropriate. The AUCinfinity ratios for oxybutynin and its metabolite with and without prior omeprazole fell within the 80% to 125% range (accepted as the criterion for bioequivalence), as did those for tolterodine and its active moiety. The peak concentration ratios for oxybutynin and metabolite also conformed to this range; those for tolterodine did not. Increasing gastric pH with omeprazole does not substantially alter the pharmacokinetic properties of extended-release oxybutynin but may alter those of extended-release tolterodine.