Pharmacokinetics/Pharmacodynamics of Dabigatran 75 mg Twice Daily in Patients With Nonvalvular Atrial Fibrillation and Severely Impaired Renal Function.

INTRODUCTION: Dabigatran etexilate is an oral direct thrombin inhibitor. Dabigatran excretion is 80% renal, so exposure increases with severity of renal failure. The US Food and Drug Administration-approved dabigatran etexilate 75 mg twice daily (BID) for patients with nonvalvular atrial fibrillation (NVAF) having severely impaired renal function (creatinine clearance: 15-30 mL/min), based on post hoc pharmacokinetic modeling. We assessed dabigatran exposure at trough and peak levels in patients with NVAF and severely impaired renal function and compared with model predictions. METHODS: Patients received dabigatran etexilate (75 mg BID) for ≥7 days before blood sampling; Cpre,ss (steady-state predose concentration; trough) was taken 10 to 16 hours postdose (prior to next dose), and C2,ss (steady-state concentration; peak) was taken 2 hours (± 30 minutes) postdose. Pharmacodynamic parameters at baseline (Ebase), trough concentrations (Epre,ss), and peak concentrations (E2,ss) were assessed by established coagulation assays. RESULTS: Of the 150 patients screened, 60 were treated, of which 40% were male and 78.3% were white; median age was 84 years. Cpre,ss values (n = 51) were close to pharmacokinetic modeling predictions with a geometric mean (gMean) of 155 ng/mL, geometric coefficient of variation (gCV) of 76.9%, and range of 15.6 to 498 ng/mL. The C2,ss values (n = 59) had a gMean of 202 ng/mL, gCV of 70.6%, and range of 42.0 to 680 ng/mL. Pharmacodynamic effects on coagulation paralleled dabigatran concentrations. Eleven (18.3%) patients had ≥1 adverse event (AE); pharmacokinetic results for these patients versus those without AEs (n = 49) were Cpre, ss: gMean = 206 versus 145 ng/mL, gCV = 64.0% versus 78.3%; C2,ss: gMean = 243 versus 193 ng/mL, gCV = 68.9% versus 70.8%. All bleeding events (8 events in 5 patients) were considered minor by the investigators. CONCLUSION: Dabigatran exposure levels largely confirmed earlier pharmacokinetic predictions, supporting the use of dabigatran etexilate 75 mg BID in patients with NVAF and severely impaired renal function. Pharmacodynamic results were also in agreement with earlier studies. TRIAL REGISTRATION: ClinicalTrials.gov NCT01896297.

Efficacy and safety of ipratropium bromide/albuterol compared with albuterol in patients with moderate-to-severe asthma: a randomized controlled trial.

BACKGROUND: Many patients with asthma require frequent rescue medication for acute symptoms despite appropriate controller therapies. Thus, determining the most effective relief regimen is important in the management of more severe asthma. This study's objective was to evaluate whether ipratropium bromide/albuterol metered-dose inhaler (CVT-MDI) provides more effective acute relief of bronchospasm in moderate-to-severe asthma than albuterol hydrofluoroalkaline (ALB-HFA) alone after 4 weeks. METHODS: In this double-blind, crossover study, patients who had been diagnosed with asthma for ≥1 year were randomized to two sequences of study medication "as needed" for symptom relief (1-7 day washout before second 4-week treatment period): CVT-MDI/ALB-HFA or ALB-HFA/CVT-MDI. On days 1 and 29 of each sequence, 6-hour serial spirometry was performed after administration of the study drug. Co-primary endpoints were FEV1 area under the curve (AUC0-6) and peak (post-dose) forced expiratory volume in 1 s (FEV1) response (change from test day baseline) after 4 weeks. The effects of "as needed" treatment with ALB-HFA/CVT-MDI were analyzed using mixed effect model repeated measures (MMRM). RESULTS: A total of 226 patients, ≥18 years old, with inadequately controlled, moderate-to-severe asthma were randomized. The study met both co-primary endpoints demonstrating a statistically significant treatment benefit of CVT-MDI versus ALB-HFA. FEV1 AUC0-6h response was 167 ml for ALB-HFA, 252 ml for CVT-MDI (p <0.0001); peak FEV1 response was 357 ml for ALB-HFA, 434 ml for CVT-MDI (p <0.0001). Adverse events were comparable across groups. CONCLUSIONS: CVT-MDI significantly improved acute bronchodilation over ALB-HFA alone after 4 weeks of "as-needed" use for symptom relief, with a similar safety profile. This suggests additive bronchodilator effects of ß2-agonist and anticholinergic treatment in moderate-to-severe, symptomatic asthma. TRIAL REGISTRATION: ClinicalTrials.gov No.: NCT00818454 ; Registered November 16, 2009.

Cause-specific mortality adjudication in the UPLIFT® COPD trial: findings and recommendations.

Mortality is an important endpoint in chronic obstructive pulmonary disease (COPD) trials, although accurately determining cause of death is difficult. In the Understanding the Potential Long-term Impacts on Function with Tiotropium (UPLIFT®) trial, a mortality adjudication committee (MAC) provided systematic, independent and blinded assessment of cause-specific mortality of all 981 reported deaths. Here we describe this process of mortality adjudication and methodological revisions introduced to help standardise the adjudication of two areas recognised to pose particular difficulty; firstly, the classification of fatal COPD exacerbations that occur in the setting of pneumonia and secondly, the categorisation of sudden death. In addition MAC determined cause of death was compared with that reported by site investigators (SIs). MAC-assigned causes of death were: respiratory, 35%; cancer, 25%; cardiovascular, 11%; sudden cardiac death, 4.4%; sudden death, 3.4%; other, 8.8%; unknown, 12.4%. Cancer/cardiac deaths were more common in Global Initiative for Chronic Obstructive Lung Disease stage II, respiratory deaths in stages III and IV. Agreement between MAC and SI regarding cause of death was complete (50.2%), incomplete (18.5%) or none (31.3%). The SI classified deaths as cardiac three-fold more frequently than MAC (incidence rate [IR]/100 patient-years 0.797 vs. 0.257), although IR ratios for cardiac deaths for tiotropium vs. control were similar between SI and MAC. Discrepancies between MAC- and SI-adjudicated causes of death are common, especially increased reporting of cardiac deaths by the SI. Future multicentre COPD trials should plan appropriate infrastructure before study initiation to ensure collection and interpretation of fatal events data.

Reaction intermediates in the catalytic mechanism of Escherichia coli MutY DNA glycosylase.

The Escherichia coli adenine DNA glycosylase, MutY, plays an important role in the maintenance of genomic stability by catalyzing the removal of adenine opposite 8-oxo-7,8-dihydroguanine or guanine in duplex DNA. Although the x-ray crystal structure of the catalytic domain of MutY revealed a mechanism for catalysis of the glycosyl bond, it appeared that several opportunistically positioned lysine side chains could participate in a secondary beta-elimination reaction. In this investigation, it is established via site-directed mutagenesis and the determination of a 1.35-A structure of MutY in complex with adenine that the abasic site (apurinic/apyrimidinic) lyase activity is alternatively regulated by two lysines, Lys142 and Lys20. Analyses of the crystallographic structure also suggest a role for Glu161 in the apurinic/apyrimidinic lyase chemistry. The beta-elimination reaction is structurally and chemically uncoupled from the initial glycosyl bond scission, indicating that this reaction occurs as a consequence of active site plasticity and slow dissociation of the product complex. MutY with either the K142A or K20A mutation still catalyzes beta and beta-delta elimination reactions, and both mutants can be trapped as covalent enzyme-DNA intermediates by chemical reduction. The trapping was observed to occur both pre- and post-phosphodiester bond scission, establishing that both of these intermediates have significant half-lives. Thus, the final spectrum of DNA products generated reflects the outcome of a delicate balance of closely related equilibrium constants.