Transmission of heat modes across a potential barrier.

Controlling the transmission of electrical current using a quantum point contact constriction paved a way to a large variety of experiments in mesoscopic physics. The increasing interest in heat transfer in such systems fosters questions about possible manipulations of quantum heat modes that do not carry net charge (neutral modes). Here we study the transmission of upstream neutral modes through a quantum point contact in fractional hole-conjugate quantum Hall states. Employing two different measurement techniques, we were able to render the relative spatial distribution of these chargeless modes with their charged counterparts. In these states, which were found to harbor more than one downstream charge mode, the upstream neutral modes are found to flow with the inner charge mode-as theoretically predicted. These results unveil a universal upstream heat current structure and open the path for more complex engineering of heat flows and cooling mechanisms in quantum nano-electronic devices.

Pharmacokinetics and pharmacodynamics of aliskiren/hydrochlorothiazide single-pill combination tablets and free combination of aliskiren and hydrochlorothiazide.

Single-pill combinations (SPCs) of complementary antihypertensive agents provide patients with a simple and effective treatment regimen. To ensure that the efficacy and safety of an SPC is the same as that for the individual drugs administered together (free combination), SPC and free-combination formulations must be shown to be bioequivalent. Three open-label, randomized studies compared the pharmacokinetics of SPC tablets of the direct renin inhibitor aliskiren and hydrochlorothiazide (HCT), at doses of 150/25, 300/12.5, and 300/25 mg, with the corresponding free combinations in healthy volunteers. Data from 2 randomized, double-blinded studies of patients with hypertension were used to assess inhibition of plasma renin activity (PRA) by the aliskiren/HCT 300/25 mg SPC and the free combination. At all dose combinations, aliskiren and HCT systemic drug exposure was similar when administered as an SPC or free combination, indicating bioequivalence. Aliskiren/HCT 300/25 mg SPC inhibited PRA to the same extent as the free combination. HCT alone increased PRA through activation of the renin-angiotensin system; aliskiren prevented this diuretic-induced increase to the same extent when administered as the free combination or as the SPC. In conclusion, aliskiren/HCT SPCs are pharmacokinetically and pharmacodynamically bioequivalent to aliskiren and HCT in free combination.

Study of the pharmacokinetic interaction of vildagliptin and metformin in patients with type 2 diabetes.

OBJECTIVE: Metformin is widely used for treating patients with type 2 diabetes, often as first-line therapy; however, many patients with type 2 diabetes are unable to maintain adequate glycemic control with metformin alone. Vildagliptin, an orally active, potent and selective dipeptidyl peptidase IV (DPP-4) inhibitor, may represent an appropriate antihyperglycemic agent for combination with metformin to improve glycemic control in such patients. This study assessed the effects of coadministration of vildagliptin and metformin on the steady-state pharmacokinetics of each drug. RESEARCH DESIGN AND METHODS: In this open-label, single-center, randomized, three-period, three-treatment crossover study, 17 patients with type 2 diabetes received vildagliptin 100 mg once daily; metformin 1000 mg once daily; or vildagliptin 100 mg once daily plus metformin 1000 mg once daily. Blood samples for pharmacokinetic sampling were taken frequently on the final day (Day 5) of each treatment period. Lack of pharmacokinetic interaction was defined as the ratio of geometric mean (GMR) and 90% confidence interval (CI) for combination:monotherapy being within the range 0.80-1.25. RESULTS: Coadministration with metformin had no effect on vildagliptin AUC(0-24) (GMR, 0.94; 90% CI 0.90, 0.99) although there was an 18% decrease in vildagliptin C(max) (GMR 0.82; 90% CI 0.73, 0.91). Coadministration with vildagliptin had no effect on metformin C(max) (GMR 1.04; 90% CI 0.94, 1.16). but caused a 15% increase in AUC(0-24) (GMR 1.15; 90% CI 1.06, 1.25). Both monotherapies and combination therapy were well tolerated. Seven patients reported a total of 10 adverse events; none was serious. CONCLUSIONS: Coadministration of vildagliptin and metformin had a small effect on the pharmacokinetics of each drug in patients with type 2 diabetes; however, this is not likely to be clinically relevant. This small, open-label trial suggests that vildagliptin could be coadministered with metformin without any dose adjustment for either agent.

Vildagliptin, a novel dipeptidyl peptidase IV inhibitor, has no pharmacokinetic interactions with the antihypertensive agents amlodipine, valsartan, and ramipril in healthy subjects.

We conducted 3 open-label, multiple-dose, 3-period, randomized, crossover studies in healthy subjects to assess the potential pharmacokinetic interaction between vildagliptin, a novel dipeptidyl peptidase IV inhibitor for the treatment of type 2 diabetes, and representatives of 3 commonly prescribed antihypertensive drug classes: (1) the calcium channel blocker, amlodipine; (2) the angiotensin receptor blocker, valsartan; and (3) the angiotensin-converting enzyme inhibitor, ramipril. Coadministration of vildagliptin 100 mg with amlodipine 5 mg, valsartan 320 mg, or ramipril 5 mg had no clinically significant effect on the pharmacokinetics of these drugs. The 90% confidence intervals of the geometric mean ratios for area under the plasma concentration-time curve from time zero to 24 hours (AUC0-24h) and maximum plasma concentration (Cmax) for vildagliptin, amlodipine, and ramipril (and its active metabolite, ramiprilat) were contained within the acceptance range for bioequivalence (0.80-1.25). Valsartan AUC0-24h and Cmax increased by 24% and 14%, respectively, following coadministration of vildagliptin, but this was not considered clinically significant. Vildagliptin was generally well tolerated when given alone or in combination with amlodipine, valsartan, or ramipril in healthy subjects at steady state. No adjustment in dosage based on pharmacokinetic considerations is required should vildagliptin be coadministered with amlodipine, valsartan, or ramipril in patients with type 2 diabetes and hypertension.

The effect of age, gender, and body mass index on the pharmacokinetics and pharmacodynamics of vildagliptin in healthy volunteers.

UNLABELLED: What is already known about this subject. Vildagliptin is a new, potent, and selective inhibitor of DPP-4. The efficacy and safety of vildagliptin in type 2 diabetes has been intensively studied in diverse subject populations. There has been little information published about the pharmacokinetics and pharmacodynamics of vildagliptin. What this study adds. No clinically relevant changes in pharmacokinetics or pharmacodynamics were observed between young and elderly, male and female, or high body mass index (BMI) and low BMI subjects. The results suggest that no dose modification is necessary for vildagliptin based on the age, gender, or BMI of a subject. AIMS: To evaluate the effect of age, gender, and body mass index (BMI) on the pharmacokinetics and pharmacodynamics of vildagliptin. METHODS: Forty healthy subjects received a single oral dose of 100 mg vildagliptin to assess the effects of age, gender, and BMI on the pharmacokinetics and pharmacodynamics, reflected by the time course of inhibition of DPP-4 activity, of vildagliptin. RESULTS: Peak concentration and exposure (AUC((0-infinity))) of vildagliptin were 17% (90% CI 2, 35%) and 31% (90% CI 18, 45%) higher in elderly vs. young subjects. Renal clearance was reduced by 32% (90% CI 17, 45%) in elderly subjects. The pharmacokinetics of vildagliptin were not significantly influenced by gender or BMI. Inhibition of DPP-4 activity was similar regardless of age, gender, or BMI. CONCLUSIONS: The pharmacokinetics of a single oral 100 mg dose of vildagliptin were not affected by gender and BMI. Exposure to vildagliptin was higher in elderly patients, but this was not associated with any difference in the effect of DPP-4 inhibition. Based on these results, no vildagliptin dose adjustment is necessary for age, gender, or BMI.

The absolute oral bioavailability and population-based pharmacokinetic modelling of a novel dipeptidylpeptidase-IV inhibitor, vildagliptin, in healthy volunteers.

BACKGROUND AND OBJECTIVE: Vildagliptin is a potent, selective, orally active inhibitor of dipeptidylpeptidase-IV being developed for the treatment of type 2 diabetes mellitus. The objective of this study was to assess the absolute oral bioavailability of vildagliptin by comparing the systemic exposure after oral and intravenous administration in healthy volunteers. METHODS: This was an open-label, randomised, two-period, two-treatment, crossover study in 11 healthy volunteers. Subjects received vildagliptin 50mg orally or 25mg as a 30-minute intravenous infusion on two occasions separated by a 72-hour washout period. Vildagliptin concentrations were determined by a specific assay in urine (lower limit of quantification [LLQ] = 5 ng/mL) and serial plasma samples (LLQ = 2 ng/mL) obtained up to 24 hours after dosing. Noncompartmental analysis and population pharmacokinetic modelling were performed. RESULTS: Both noncompartmental analysis and population pharmacokinetic modelling estimated the absolute oral bioavailability of vildagliptin to be 85%. Renal elimination of unchanged vildagliptin accounted for 33% and 21% of the administered dose 24 hours after intravenous and oral administration, respectively. Renal clearance (13 L/h) was approximately one-third of the total systemic clearance (41 L/h). Two peaks were observed in plasma concentrations at 1 and 3 hours after oral administration in nine of 11 subjects. Modelling based on the population approach identified two absorption sites with lag-times of 0.225 and 2.46 hours. Both absorption rate constants were slower than the elimination rate constant, indicating 'flip-flop' kinetics after oral administration. Bodyweight was identified as a factor with an impact on the volume of distribution of the peripheral compartment. Clearance was 24% greater in males (44.6 L/h) than in females (36.1 L/h). CONCLUSIONS: Vildagliptin is rapidly and well absorbed with an estimated absolute bioavailability of 85%. Two possible sites of absorption were identified, and the absorption rates were slower than the elimination rate, indicating a flip-flop phenomenon after oral dosing.

Evaluation of pharmacokinetic interactions between vildagliptin and digoxin in healthy volunteers.

Vildagliptin is a novel antidiabetic agent that is an orally active, potent, and selective inhibitor of dipeptidyl peptidase IV, the enzyme responsible for degradation of the incretin hormones. This open-label, randomized, 3-period crossover study investigated the potential for pharmacokinetic interactions in 18 healthy subjects during coadministration of vildagliptin and digoxin. Subjects were randomized to receive each of 3 treatments: vildagliptin 100 mg qd, digoxin (0.5 mg, then 0.25 mg qd on days 2-7), and the combination vildagliptin/digoxin for 7 days. Coadministration of digoxin with vildagliptin had no effect on exposure to vildagliptin (geometric mean ratios [90% confidence interval]: AUC(0-24h), 0.99 [0.95-1.03]; C(max), 0.95 [0.85-1.06]) or to digoxin (AUC(0-24h), 1.02 [0.94-1.12]; C(max), 1.08 [0.97-1.20]). In addition, no changes in t(max), t((1/2)), and CL/F were observed for either drug. These results indicate that no dose adjustment is necessary when vildagliptin and digoxin are coadministered.

Dose proportionality and the effect of food on vildagliptin, a novel dipeptidyl peptidase IV inhibitor, in healthy volunteers.

Vildagliptin is a potent and selective dipeptidyl peptidase IV inhibitor in development for the treatment of type 2 diabetes that improves glycemic control by enhancing alpha- and beta-cell responsiveness to glucose. Two open-label, single-dose, randomized, crossover studies in healthy subjects (ages 18-45 years) investigated the dose proportionality of vildagliptin pharmacokinetics (n = 20) and the effect of food (n = 24) on vildagliptin pharmacokinetics. There was a linear relationship (r(2) = 0.999) between vildagliptin doses of 25, 50, 100, and 200 mg and area under the plasma concentration-time curve from time zero to infinity (AUC(0-infinity)) and maximum plasma concentration (C(max)). Dose proportionality was assessed using a statistical power model [X = alpha x (dose)(beta)]. The 90% confidence intervals of the proportionality coefficient, beta, for AUC(0-infinity) (1.15-1.19) and C(max) (1.04-1.14) indicated that deviations from dose proportionality were small (<7.7%). Doubling of dose led to 2.1- to 2.3-fold increases in AUC(0-infinity) and C(max) but no dose-dependent changes in time to reach C(max) or terminal elimination half-life. Administration of vildagliptin 100 mg following a high-fat meal decreased C(max) by 19% and AUC(0-infinity) by 10%. Vildagliptin displays approximately dose-proportional pharmacokinetics over the 25- to 200-mg dose range, and administration with food has no clinically relevant effect on vildagliptin pharmacokinetics.

Effect of the novel oral dipeptidyl peptidase IV inhibitor vildagliptin on the pharmacokinetics and pharmacodynamics of warfarin in healthy subjects.

OBJECTIVE: Vildagliptin is a potent and selective dipeptidyl peptidase-IV (DPP-4) inhibitor that improves glycemic control in patients with type 2 diabetes by increasing alpha and beta-cell responsiveness to glucose. This study assessed the effect of multiple doses of vildagliptin 100 mg once daily on warfarin pharmacokinetics and pharmacodynamics following a single 25 mg oral dose of warfarin sodium. RESEARCH DESIGN AND METHODS: Open-label, randomized, two-period, two-treatment crossover study in 16 healthy subjects. RESULTS: The geometric mean ratios (co-administration vs. administration alone) and 90% confidence intervals (CIs) for the area under the plasma concentration-time curve (AUC) of vildagliptin, R- and S-warfarin were 1.04 (0.98, 1.11), 1.00 (0.95, 1.04) and 0.97 (0.93, 1.01), respectively. The 90% CI of the ratios for vildagliptin, R- and S-warfarin maximum plasma concentration (Cmax) were also within the equivalence range 0.80-1.25. Geometric mean ratios (co-administration vs. warfarin alone) of the maximum value and AUC for prothrombin time (PT(max), 1.00 [90% CI 0.97, 1.04]; AUC(PT), 0.99 [0.97, 1.01]) and international normalized ratios (INRmax, 1.01 [0.98, 1.05]; AUC(INR), 0.99 [0.97, 1.01]) were near unity with the 90% CI within the range 0.80-1.25. Vildagliptin was well tolerated alone or co-administered with warfarin; only one adverse event (upper respiratory tract infection in a subject receiving warfarin alone) was reported, which was judged not to be related to study medication. CONCLUSIONS: Co-administration of warfarin with vildagliptin did not alter the pharmacokinetics and pharmacodynamics of R- or S-warfarin. The pharmacokinetics of vildagliptin were not affected by warfarin. No dosage adjustment of either warfarin or vildagliptin is necessary when these drugs are co-medicated.