Thermal Hydroquinone Oxidation on Co/N-doped Carbon Proceeds by a Band-Mediated Electrochemical Mechanism.

Molecular metal complexes catalyze aerobic oxidation reactions via redox cycling at the metal center to effect sequential activation of O2 and the substrate. Metal surfaces can catalyze the same transformations by coupling independent half-reactions for oxygen reduction and substrate oxidation mediated via the exchange of band-electrons. Metal- and nitrogen-doped carbons (MNCs) are promising catalysts for aerobic oxidation that consist of molecule-like active sites embedded in conductive carbon hosts. Owing to their combined molecular and metallic features, it remains unclear whether they catalyze aerobic oxidation via the sequential redox cycling pathways of molecules or band-mediated pathways of metals. Herein, we simultaneously track the potential of the catalyst and the rate of turnover of aerobic hydroquinone oxidation on a cobalt-based MNC catalyst in contact with a carbon electrode. By comparing operando measurements of rate and potential with the current-voltage behavior of each constituent half-reaction under identical conditions, we show that these molecular materials can display the band-mediated reaction mechanisms of extended metallic solids. We show that the action of these band-mediated mechanisms explains the fractional reaction orders in both oxygen and hydroquinone, the time evolution of catalyst potential and rate, and the dependence of rate on the overall reaction free energy. Selective poisoning experiments suggest that oxygen reduction proceeds at cobalt sites, whereas hydroquinone oxidation proceeds at native carbon-oxide defects on the MNC catalyst. These findings highlight that molecule-like active sites can take advantage of band-mediated mechanisms when coupled to conductive hosts.

Redox-Induced Structural Reorganization Dictates Kinetics of Cobalt(III) Hydride Formation via Proton-Coupled Electron Transfer.

Two-electron, one-proton reactions of a family of [CoCp(dxpe)(NCCH3)]2+ complexes (Cp = cyclopentadienyl, dxpe = 1,2-bis(di(aryl/alkyl)phosphino)ethane) form the corresponding hydride species [HCoCp(dxpe)]+ (dxpe = dppe (1,2-bis(diphenylphosphino)ethane), depe (1,2-bis(diethylphosphino)ethane), and dcpe (1,2-bis(dicyclohexylphosphino)ethane)) through a stepwise proton-coupled electron transfer process. For three [CoCp(dxpe)(NCCH3)]2+ complexes, peak shift analysis was employed to quantify apparent proton transfer rate constants from cyclic voltammograms recorded with acids ranging 22 pKa units. The apparent proton transfer rate constants correlate with the strength of the proton source for weak acids, but these apparent proton transfer rate constants curiously plateau (kpl) as the reaction becomes increasingly exergonic. The absolute apparent proton transfer rate constants across both these regions correlate with the steric bulk of the chelating diphosphine ligand, with bulkier ligands leading to slower kinetics (kplateau,depe = 3.5 × 107 M-1 s-1, kplateau,dppe = 1.7 × 107 M-1 s-1, kplateau,dcpe = 7.1 × 104 M-1 s-1). Mechanistic studies were conducted to identify the cause of the aberrant kPTapp-ΔpKa trends. When deuterated acids are employed, deuterium incorporation in the Cp ring is observed, indicating protonation of the CoCp(dxpe) species to form the corresponding hydride proceeds via initial ligand protonation. Digital simulations of cyclic voltammograms show ligand loss accompanying initial reduction gates subsequent PCET activity at higher driving forces. Together, these experiments reveal the details of the reaction mechanism: reduction of the Co(III) species is followed by dissociation of the bound acetonitrile ligand, subsequent reduction of the unligated Co(II) species to form a Co(I) species is followed by protonation, which occurs at the Cp ring, followed by tautomerization to generate the stable Co(III)-hydride product [HCoCp(dxpe)]+. Analysis as a function of chelating disphosphine ligand, solvent, and acid strength reveals that the ligand dissociation equilibrium is directly influenced by the steric bulk of the phosphine ligands and gates protonation, giving rise to the plateau of the apparent proton transfer rate constant with strong acids. The complexity of the reaction mechanism underpinning hydride formation, encompassing dynamic behavior of the entire ligand set, highlights the critical need to understand elementary reaction steps in proton-coupled electron transfer reactions.

Proton-Coupled Electron Transfer Reactions with Photometric Bases Reveal Free Energy Relationships for Proton Transfer.

The proton-coupled electron transfer (PCET) oxidation of p-aminophenol in acetonitrile was initiated via stopped-flow rapid-mixing and spectroscopically monitored. For oxidation by ferrocenium in the presence of 7-(dimethylamino)quinoline proton acceptors, both the electron transfer and proton transfer components could be optically monitored in the visible region; the decay of the ferrocenium absorbance is readily monitored (λmax = 620 nm), and the absorbance of the 2,4-substituted 7-(dimethylamino)quinoline derivatives (λmax = 370-392 nm) red-shifts substantially (ca. 70 nm) upon protonation. Spectral analysis revealed the reaction proceeds via a stepwise electron transfer-proton transfer process, and modeling of the kinetics traces monitoring the ferrocenium and quinolinium signals provided rate constants for elementary proton and electron transfer steps. As the pKa values of the conjugate acids of the 2,4-R-7-(dimethylamino)quinoline derivatives employed were readily tuned by varying the substituents at the 2- and 4-positions of the quinoline backbone, the driving force for proton transfer was systematically varied. Proton transfer rate constants (kPT,2 = (1.5-7.5) × 10(8) M(-1) s(-1), kPT,4 = (0.55-3.0) × 10(7) M(-1) s(-1)) were found to correlate with the pKa of the conjugate acid of the proton acceptor, in agreement with anticipated free energy relationships for proton transfer processes in PCET reactions.

Efficacy and safety of azelastine 0.15% nasal spray administered once daily in patients with allergy to Texas mountain cedar pollen.

BACKGROUND: A previous study with azelastine nasal spray in patients with seasonal allergic rhinitis (SAR) demonstrated that increasing the azelastine concentration from 0.1% to 0.15% allowed for once-daily dosing without increasing the incidence of adverse effects. This study evaluated the efficacy of azelastine 0.15% nasal spray administered once daily for treating symptoms of SAR. METHODS: In this 14-day, randomized, double-blind, placebo-controlled study, patients with moderate-to-severe SAR were randomized to azelastine 0.15% (n = 251) or placebo (n = 255), both at a dosage of 2 sprays/nostril once daily. The primary efficacy variable was change from baseline in the 12-hour reflective Total Nasal Symptom Score (TNSS). Key secondary variables were change from baseline in 24-hour instantaneous TNSS, to establish the dosing interval, and change from baseline in the Total Ocular Symptom Score (TOSS). RESULTS: The mean improvement (3.57) and percentage improvement (19.3%) in 12-hour reflective TNSS was significant (p < 0.012) with azelastine 0.15% compared to placebo (2.14 and 11.4%, respectively). The mean improvement in 24-hour instantaneous TNSS was also significant (p < 0.001) for azelastine 0.15% compared to placebo, indicating efficacy with once-daily dosing. The overall improvement and percentage improvement in TOSS was significant (p ≤ 0.012) with azelastine 0.15% (2.21 and 16.7%, respectively) compared to placebo (1.28 and 6.0%, respectively). The overall score for the Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) was significantly (p < 0.001) improved from baseline in the azelastine group compared with the placebo group. Nasal discomfort (3.6%) and bitter taste (2.4%) were the most common adverse events. There were no reports of somnolence with azelastine. CONCLUSION: Azelastine 0.15% was effective and well tolerated with once-daily dosing. Azelastine 0.15% nasal spray significantly improved a complex of eye symptoms compared to placebo.

Efficacy and safety of azelastine 0.15% nasal spray administered once daily in subjects with seasonal allergic rhinitis.

Azelastine nasal spray is commercially available as a 0.1% w/v solution and is recommended for twice-daily dosing. Increasing the azelastine concentration to 0.15% may be effective with once-daily dosing without increasing the incidence of adverse events. This study evaluated the efficacy and safety of azelastine 0.15% nasal spray at a dosage of 2 sprays/nostril once daily. This randomized, double-blind, placebo-controlled study was conducted in subjects with moderate-to-severe seasonal allergic rhinitis (SAR) during the 2007/2008 Texas Mountain Cedar season. In total, 536 subjects were randomized to 2 sprays/nostril once daily (A.M.) of azelastine 0.15% or placebo. The primary efficacy variable was change from baseline in a 12-hour reflective Total Nasal Symptom Score (TNSS), consisting of nasal congestion, runny nose, itchy nose, and sneezing. The key secondary variable was change from baseline in 24-hour instantaneous TNSS, which determines the duration of action and effective dosing interval. After 2 weeks, the mean improvement in 12-hour reflective TNSS and percentage improvement in 12-hour reflective TNSS were significant (p < 0.001) with azelastine 0.15% (19%) compared with placebo (10%). The improvement in 24-hour instantaneous TNSS also was significant (p < 0.001) for azelastine 0.15% compared with placebo, supporting efficacy with once-daily dosing. All individual TNSS symptoms were significantly (p < 0.01) improved with azelastine 0.15% compared with placebo. With the exception of bitter taste (4.5%) and nasal discomfort (4.5%), adverse events with azelastine 0.15% were reported with an incidence similar to placebo. Azelastine 0.15% nasal spray was effective and well tolerated in subjects with SAR with once-daily dosing.

Budesonide turbuhaler delivered once daily improves health-related quality of life in adult patients with non-steroid-dependent asthma.

Budesonide inhalation powder via the dry-powder multidose inhaler Turbuhaler (budesonide Turbuhaler) has been shown to improve lung function and symptoms in adults with asthma. In this double-blind, placebo-controlled, multicenter trial, we evaluated the effects of once-daily budesonide Turbuhaler on health-related quality of life (HRQL) in 177 adults (aged 18-70 years) with non-steroid-dependent asthma. Patients were randomized to receive budesonide Turbuhaler (400 micrograms) once daily or placebo for 12 weeks. HRQL was assessed at baseline and weeks 4 and 12 using the Asthma Quality of Life Questionnaire (AQLQ). In addition to assessment based on the four AQLQ domains (activity limitations, asthma symptoms, emotional function, and response to exposure to environmental stimuli), AQLQ overall scores were analyzed for both treatment groups. Compared with placebo, patients using budesonide Turbuhaler once daily had statistically significant (p < 0.001) improvements from baseline to weeks 4 and 12 in AQLQ overall scores. Statistically significant improvements from baseline to weeks 4 and 12 in all four individual domains also were observed in the budesonide Turbuhaler group compared with placebo. Differences between the two treatment groups in mean changes from baseline in AQLQ overall, asthma symptoms, and emotional function reached the level required for patients to achieve a minimal important difference of change (> or = 0.5 U) at week 12. A retrospective analysis of the data showed that approximately 70% of patients treated with budesonide Turbuhaler experienced a minimal important difference of change in AQLQ overall scores. Overall, improvements in AQLQ correlated significantly (p < or = 0.04) with improvements in forced expiratory volume in 1 second, morning peak expiratory flow measurements, asthma symptoms, and breakthrough bronchodilator use at the study end. Thus, patients with corticosteroid-naïve asthma can experience improved HRQL when using budesonide Turbuhaler.

Fluticasone propionate aqueous nasal spray provided significantly greater improvement in daytime and nighttime nasal symptoms of seasonal allergic rhinitis compared with montelukast.

BACKGROUND: The safety and efficacy of intranasal corticosteroids for the treatment of allergic rhinitis is well documented in the literature. Additionally, an expert panel has concluded that intranasal corticosteroids are the first line of therapy when obstruction is a major component of rhinitis. Montelukast is a leukotriene receptor antagonist recently approved for the treatment of seasonal allergic rhinitis (SAR). OBJECTIVE: This randomized, double-blind, double-dummy, parallel-group study was conducted to compare the effectiveness of a 15-day course of intranasal fluticasone propionate 200 microg, once daily (FP200QD), to oral montelukast 10 mg, once daily (MON10QD), in relieving daytime and nighttime nasal symptoms associated with SAR. METHODS: The intent-to-treat (ITT) analysis population consisted of 705 eligible males and females (> or = 15 years) with SAR randomized to either FP200QD (N = 353) or MON10QD (N = 352). The primary efficacy endpoint was the mean change from baseline in subject-rated daytime total nasal symptom scores (the sum of four individual scores: nasal congestion, itching, rhinorrhea, and sneezing), evaluated via visual analog scales, and averaged over weeks 1 to 2. Secondary endpoints included the four daytime individual nasal symptom scores, the nighttime total, and individual nasal symptom scores (each evaluated on a four-point scale from 0 to 3). RESULTS: Statistically significant differences favoring FP200QD over MON10QD were observed for the mean change from baseline in daytime total nasal symptom scores (P < 0.001), daytime individual nasal symptom scores (P < 0.001), nighttime total (P < 0.001), and all individual nasal symptom scores (P < or = 0.002) over the 15-day treatment period. FP200QD and MON10QD were both well tolerated. CONCLUSIONS: The results of this well controlled study demonstrated that FP200QD was consistently superior to MON10QD with regard to every efficacy endpoint evaluated, including daytime and nighttime nasal congestion, in subjects with SAR.

Inhaled insulin using the AERx Insulin Diabetes Management System in healthy and asthmatic subjects.

OBJECTIVE: The AERx insulin Diabetes Management System (AERx iDMS) (Aradigm, Hayward, CA) delivers an aerosol of liquid human insulin to the deep lung for systemic absorption. This study examined the effects on pulmonary function, pharmacokinetics, and pharmacodynamics of inhaled insulin in asthmatic and nonasthmatic subjects without diabetes. RESEARCH DESIGN AND METHODS: A total of 28 healthy and 17 asthmatic (forced expiratory volume during the first second [ FEV(1)] 50-80% of predicted value) subjects were enrolled in a two-part, open-label trial. To assess insulin pharmacokinetics and pharmacodynamics, a single inhalation dose of 1.57 mg (45 IU) was given on each of the 2 dosing days in part 1. A dose of 4.7 mg (135 IU) of insulin was inhaled in part 2 to assess effects on pulmonary function. RESULTS: Inhaled insulin showed area under the curve (AUC)((0-360 min)) values that were significantly greater for healthy subjects than for asthmatic subjects (P = 0.013), whereas no difference was observed for maximum concentration (C(max)) in the two groups. A greater reduction of serum glucose as indicated by area over the curve (AOC)((0-360 min)) was observed in healthy subjects (P = 0.007). Asthmatic subjects had greater intrasubject variations in insulin AUC((0-360 min)) and C(max) values than healthy subjects, but similar variations in glucose AOC((0-360 min)). No significant changes in FEV(1), forced vital capacity (FVC), and FEV(1)/FVC were observed from pre- to postdose times, and there were no observed safety issues. CONCLUSIONS: After inhaling insulin using the AERx iDMS, asthmatic subjects absorbed less insulin than healthy subjects, resulting in less reduction of serum glucose. No effects on airway reactivity were observed. Diabetic patients with asthma may need to inhale more insulin than patients with normal respiratory function in order to achieve similar glycemic control.

Relief of sinus pain and pressure with fluticasone propionate aqueous nasal spray: a placebo-controlled trial in patients with allergic rhinitis.

Although allergic rhinitis is commonly associated most with symptoms of nasal congestion, rhinorrhea, sneezing, and itching, the symptom of sinus pain and pressure often prompts the patient to seek medical attention. The effect of fluticasone propionate on this symptom has not been studied. The purpose of this study was to compare the efficacy and safety of fluticasone propionate aqueous nasal spray to placebo vehicle in the treatment of patients with sinus pain and pressure arising from allergic rhinitis. A multicenter, double-blind, parallel-group trial was conducted in 206 symptomatic patients > or = 12 years with seasonal or perennial allergic rhinitis. Patients were treated for 14 days with either fluticasone propionate aqueous nasal spray, 200 mcg once daily, or placebo vehicle. Patients attended clinic visits and kept diary cards rating sinus pain and pressure (measured as one symptom) and nasal congestion symptoms during the study. Treatment with fluticasone propionate provided significantly greater relief of symptoms of sinus pain and pressure compared with placebo over the entire 14-day treatment period. Nasal congestion scores also were significantly reduced compared with placebo at each time point. Treatments were well tolerated, and the incidence of adverse events attributable to study treatments was similar between groups. Our data indicate that symptoms of sinus pain and pressure and nasal congestion can be significantly reduced in patients with allergic rhinitis when treated with fluticasone propionate aqueous nasal spray, 200 mcg once daily.