Oral therapies for the treatment of pulmonary arterial hypertension

Background and objective

Pulmonary arterial hypertension (PAH) is a rare but life-threatening condition that is characterized by progressive elevation of pulmonary artery pressure and pulmonary vascular resistance, leading to right-sided heart failure and frequently death. Orally administered agents used for the treatment of symptomatic, moderate-to-severe PAH include sildenafil and the endothelin (ET) receptor antagonists (ERAs), bosentan and sitaxentan (sitaxsentan). Ambrisentan is a new oral ETA receptor-selective ERA, with higher ET receptor affinity than bosentan. Placebo-controlled, randomized clinical trials (RCTs) have demonstrated that ambrisentan (5 or 10mg/day) is safe and effective. To provide health economic data on the multiple oral PAH therapies currently available, a population-based cost-minimization analysis (CMA) was conducted for Canada.

Methods

The primary requirement for a CMA is that all clinical outcomes be equivalent between comparator treatments. To provide such supporting data, a literature search was conducted for RCTs of oral agents used to treat symptomatic PAH. This was followed by application of direct and indirect statistical methods to support the hypothesis of clinical equivalence between the oral agents. Estimates for PAH prevalence, incidence and death rates were then used to build a population-based CMA model. The base-case analysis considered costs for drug therapy, outpatient pharmacy costs, medical consultations and visits, laboratory and diagnostic procedures and other healthcare-related resources. In addition, costs for secondary pharmacotherapy in cases where the primary agent had to be discontinued because of adverse effects were also included. The time horizon for evaluating pharmacotherapy was 3 years, all costs were in 2008 Canadian dollars ($Can) and the costs were discounted at a rate of 3% annually. The study perspective was the Canadian healthcare system.

Results

There were no double-blind RCTs comparing ambrisentan with any of the other oral agents. Therefore, an indirect comparison of placebo-controlled trials of PAH drugs had to be used to support the clinical equivalence. This included a calculation of standardized mean differences (SMD) between agents (vs placebo) and a meta-regression analysis on the primary and secondary trial endpoints. Keeping in mind the caveats associated with indirect trial comparisons, the data suggested similar clinical efficacy over 12–16 weeks between agents, as indicated by the identical magnitude of the SMD between the active agent and placebo and the non-significant differences between drugs as determined by the meta-regression analysis. The population-based model projected that the number of PAH patients clinically suitable for these drugs in Canada would be 931 in the first full-budget year (i.e. 2009) with an increase to 1114 by the third full year. The CMA revealed the following rank order of the least to most costly agent; sildenafil, ambrisentan, sitaxentan and bosentan. Sildenafil was the least costly, primarily because of the lower daily drug-acquisition cost. Of the three ERAs, ambrisentan would be associated with annual cost savings of $Can3.4 and $Can5.6 million when used as an alternative to sitaxentan or bosentan, respectively.

Conclusions

Ambrisentan is less costly than other available ERAs, including bosentan and sitaxentan, but is more costly than sildenafil. In PAH patients in whom an ERA is the preferred agent, ambrisentan may be the drug of choice because of its economic advantages and improved safety profile.     

Performance-based or self-report measures of physical function: which should be used in clinical trials of hip fracture patients?

Latham NK, Mehta V, Nguyen AM, Jette AM, Olarsch S, Papanicolaou D, Chandler J. Performance-based or self-report measures of physical function: which should be used in clinical trials of hip fracture patients?

Objectives

To assess the validity, sensitivity to change, and responsiveness of 3 self-report and 4 performance-based measures of physical function: activity measure for postacute care (AM-PAC) Physical Mobility and Personal Care scales, the Medical Outcomes Study 36-Item Short Form Health Survey Physical Function scale (SF-36 PF), the Physical Functional Performance test (PFP-10), the Short Physical Performance Battery (SPPB), a 4-meter gait speed, and the six-minute walk test (6MWT).

Design

A prospective observational study of patients after a hip fracture. Assessments were performed at baseline and 12 weeks postenrollment.

Setting

Inpatient and outpatient rehabilitation facilities in Norway, the United Kingdom, Sweden, Israel, Germany, the United States, Denmark, and Spain.

Participants

A sample of study participants (N=108) who had a hip fracture.

Interventions

Not applicable.

Main Outcome Measures

Assessments of validity (known-groups, concurrent, construct, and predictive), sensitivity to change (effect size, standardized response mean [SRM], SE of measure, minimal detectable change (MDC), and responsiveness (optimal operating cut-points and area under the curve) between baseline and 12-week follow-up.

Results

All physical function measures achieved comparably acceptable levels of validity. Odds ratios in predicting patient Global Assessment of Improvement at 12 weeks were as follows: AM-PAC Physical Mobility scale, 5.3; AM-PAC Personal Care scale, 3.6; SF-36 PF, 4.3; SPPB, 2.0; PFP-10, 2.5; gait speed, 1.9; and 6MWT, 2.4. Effect sizes and SRM exceeded 1 SD for all 7 measures. Percent of patients who exceeded the MDC₉₀ at week 12 were as follows: AM-PAC Physical Mobility scale, 90%; AM-PAC Personal Care scale, 74%; SF-36 PF, 66%; SPPB, 36%; PFP-10, 75%; gait speed, 69%; and 6MWT, 75%. When evaluating responsiveness using the area under receiver operating curves for each measure, all measures had acceptable responsiveness, and no pattern emerged of superior responsiveness depending on the type of measure used.

Conclusions

Findings reveal that the validity, sensitivity, and responsiveness of self-report measures of physical function are comparable to performance-based measures in a sample of patients followed after fracturing a hip. From a psychometric perspective, either type of functional measure would be suitable for use in clinical trials where improvement in function is an endpoint of interest. The selection of the most appropriate type of functional measure as the primary endpoint for a clinical trial will depend on other factors, such as the measure's feasibility or the strength of the association between the hypothesized mechanism of action of the study intervention and a functional outcome measure.     

Antioxidant activity and total phenolic content of ethanolic extract of Caesalpinia bonducella seeds

The aim of this study was to assess the in vitro potential of ethanolic extract of Caesalpinia bonducella seeds as a natural antioxidant. The DPPH activity of the extract (20, 40, 50, 100 and 200 μg/ml) was increased in a dose dependent manner, which was found in the range of 38.93–74.77% as compared to ascorbic acid (64.26–82.58%). The IC₅₀ values of ethanolic extract and ascorbic acid in DPPH radical scavenging assay were obtained to be 74.73 and 26.68 μg/ml, respectively. The ethanolic extract was also found to scavenge the superoxide generated by EDTA/NBT system. Measurement of total phenolic content of the ethanolic extract of C. bonducella was achieved using Folin–Ciocalteau reagent containing 62.50 mg/g of phenolic content, which was found significantly higher when compared to reference standard gallic acid. The ethanolic extract also inhibited the hydroxyl radical, nitric oxide, superoxide anions with IC₅₀ values of 109.85, 102.65 and 89.84 μg/ml, respectively. However, the IC₅₀ values for the standard ascorbic acid were noted to be 70.79, 65.98 and 36.68 μg/ml respectively. The results obtained in this study clearly indicate that C. bonducella has a significant potential to use as a natural antioxidant agent.     

In vitro antioxidant activity and total phenolic content of ethanolic leaf extract of Stevia rebaudiana Bert.

The aim of this study was to assess the in vitro potential of ethanolic leaf extract of Stevia rebaudiana as a natural antioxidant. The DPPH activity of the extract (20, 40, 50, 100 and 200 μg/ml) was increased in a dose dependent manner, which was found in the range of 36.93–68.76% as compared to ascorbic acid 64.26–82.58%. The IC₅₀ values of ethanolic extract and ascorbic acid in DPPH radical scavenging assay were obtained to be 93.46 and 26.75 μg/ml, respectively. The ethanolic extract was also found to scavenge the superoxide generated by EDTA/NBT system. Measurement of total phenolic content of the ethanolic extract of S. rebaudiana was achieved using Folin–Ciocalteau reagent containing 61.50 mg/g of phenolic content, which was found significantly higher when compared to reference standard gallic acid. The ethanolic extract also inhibited the hydroxyl radical, nitric oxide, superoxide anions with IC₅₀ values of 93.46, 132.05 and 81.08 μg/ml, respectively. However, the IC₅₀ values for the standard ascorbic acid were noted to be 26.75, 66.01 and 71.41 μg/ml respectively. The results obtained in this study clearly indicate that S. rebaudiana has a significant potential to use as a natural antioxidant agent.     

Dietary behaviors predict glycemic control in youth with type 1 diabetes

OBJECTIVE—To investigate the association between dietary adherence and glycemic control among youth with type 1 diabetes.RESEARCH DESIGN AND METHODS—We conducted a cross-sectional analysis of 119 youth aged 9–14 years (mean ± SD 12.1 ± 1.6 years) with diabetes duration ≥1 year (5.4 ± 3.1 years). Dietary adherence was assessed using the Diabetes Self-Management Profile diet domain. Higher score defined greater dietary adherence. Glycemic control was determined by A1C.RESULTS—Dietary adherence score was inversely correlated with A1C (r = −0.36, P < 0.0001). In a multivariate model (R² = 0.34, P < 0.0001), dietary adherence (P = 0.004), pump use (P = 0.03), and caregiver education (P = 0.01) were associated with A1C. A1C of youth in the lowest (9.0%) tertile of diet score was higher than A1C of youth in the middle (8.1%, P = 0.004) and upper (8.4%, P = 0.06) tertiles. Dietary adherence uniquely explained 8% of the variance in A1C in the model.CONCLUSIONS—Greater dietary adherence was associated with lower A1C among youth with type 1 diabetes.Data for youth with type 1 diabetes demonstrate a gap between attained glycemic control and age-specific goals (1–3). With intensive insulin therapy, dietary behaviors become central to optimizing glycemic control. Studies have shown that greater dietary adherence improves glycemic control among adults with type 1 diabetes (4,5). In this study, we investigated the relationship between dietary adherence and glycemic control in youth with type 1 diabetes.     

The effect of altitude on dosing and response to erythropoietin in ESRD

For poorly understood reasons, patients with end-stage renal disease (ESRD) differ substantially in their response to treatment with recombinant erythropoietin (EPO). Because hypoxia influences many of the biologic pathways involved in erythropoiesis, the altitude at which a patient lives may affect the dose-response relationship of EPO. In this retrospective cohort study, clinical data from 341,737 incident hemodialysis patients registered in the U.S. Renal Data System were combined with elevation data from the U.S. Geological Survey to address this question. Higher altitude was associated with smaller EPO doses and higher hematocrit levels. For example, compared with patients at sea level, patients living above 6000 ft received 19% less EPO (12.9 versus 15.9 thousand units/wk) but had hematocrit levels 1.1 points higher (35.7% versus 34.6%). These associations were found within subgroups defined by sex, race, age, calendar time, cause of ESRD, and dialysis center profit status, and persisted after adjustment for various potential confounding factors. Furthermore, resistance to EPO decreased with elevation. Our results suggest that ESRD patients living at high altitude either increase endogenous EPO production or respond better to endogenous and exogenous EPO.