The effects of CYP3A4 induction and inhibition on the pharmacokinetics of alisporivir in humans

In vitro data suggest that alisporivir is a substrate and inhibitor of CYP3A4 and P-gp. Hence, the potential for drug-drug interactions when alisporivir is co-administered with CYP3A4 and/or P-gp inhibitors such as ketoconazole, azithromycin and CYP3A4 inducers such as rifampin were evaluated in three separate clinical studies. Co-administration with ketoconazole (a strong CYP3A4 inhibitor) increased the Cmax , AUC and terminal elimination half-life of alisporivir by approximately two-, eight- ,and threefold, respectively. Co-administration with azithromycin (a putative weak CYP3A4 inhibitor and substrate) had no impact on the Cmax and AUC of alisporivir. Rifampin (a CYP3A4 inducer) caused an approximate 90% reduction in alisporivir Cmax and AUC and a fourfold reduction in alisporivir terminal elimination half-life. Alisporivir as an inhibitor of CYP3A4 caused a 39% increase in azithromycin exposure. The results from these studies establish alisporivir as a sensitive CYP3A4 substrate in vivo. Consequently, co-administered potent CYP3A4 inhibitors and inducers are likely to cause clinically significant changes in the exposure to alisporivir.

Pharmacokinetic and pharmacodynamic drug-drug interaction assessment between pradigastat and digoxin or warfarin

Pradigastat, a novel diacylglycerol acyltransferase-1 inhibitor, was evaluated for both pharmacokinetic (PK) and pharmacodynamic (PD) drug-drug interactions when co-administered with digoxin or warfarin in healthy subjects. This open-label study included two parallel subject cohorts each with three sequential treatment periods. Forty subjects were enrolled in the study with 20 subjects allocated to each cohort. PK and PD (PT/INR for warfarin only) samples were collected in each period. The statistical analysis results showed that the 90% CIs of the geometric mean ratios of digoxin, R-warfarin, and S-warfarin PK parameters (AUC and Cmax) were all within 0.80-1.25 interval. The 90% CIs of the geometric mean ratios of pradigastat PK parameters (AUC and Cmax) were within 0.80-1.25 interval when co-administered with warfarin; while co-administration with digoxin slightly reduced pradigastat exposure (∼15%). The results also showed that 90% CIs of the geometric mean ratios of warfarin PD parameters (AUC(PT), PTmax, AUC(INR), and INRmax) were within 0.80-1.25 interval. Pradigastat and digoxin or warfarin had no relevant clinical PK or PD drug-drug interactions. Administration of pradigastat and warfarin or pradigastat and digoxin as a mono or combined treatment appears to be safe and tolerated.

Abstract 449: Assessment of Pharmacokinetic Drug Interaction Between LCZ696 and Digoxin

Objective: LCZ696 is a first-in-class angiotensin receptor neprilysin inhibitor (ARNI) being developed for the treatment of cardiovascular diseases including hypertension and heart failure. Ingestion of LCZ696 results in systemic exposure to AHU377 (an inactive prodrug converted to LBQ657, a neprilysin inhibitor) and valsartan (angiotensin receptor inhibitor). Digoxin, a narrow therapeutic index drug, is a commonly administered medication to heart failure patients. Since LCZ696 and digoxin may be co-administered in this patient population, this study was conducted to evaluate the pharmacokinetic drug-drug interaction potential between LCZ696 and digoxin.

Methods: This study employed an open label, two-period, single sequence study design in 24 healthy subjects. In period 1, subjects received 200 mg LCZ696 b.i.d for 3 days and a single dose of 200 mg LCZ696 on Day 4 morning. Following a 4-7 day washout, in period 2, all subjects received 0.25 mg digoxin q.d. for 14 days and 200 mg LCZ696 b.i.d co-administered from Day 11 to Day 14. Serial PK samples were collected in both treatment periods and analyzed using validated LC/MS/MS bioanalytical methods. The PK parameters including Cmaxss and AUCtau of LCZ696 analytes (LBQ657, valsartan) and digoxin were determined using non-compartmental analysis and the results were statistically evaluated.

Results: The 90% confidence intervals of the geometric mean ratios (test/reference) for Cmaxss and AUCtau of digoxin were within the 0.8-1.25 range indicating that LCZ696 did not affect the PK of digoxin. Similarly, the 90% confidence intervals of the geometric mean ratios for Cmaxss and AUCtau for both LBQ657 and valsartan were within the 0.8-1.25 range indicating that digoxin did not affect the PK of LCZ696 analytes.

Conclusion: After co-administration of LCZ696 200 mg b.i.d with digoxin 0.25 mg q.d., exposures of digoxin and the LCZ696 analytes (LBQ657 and valsartan) remained unchanged. LCZ696 200 mg b.i.d was safe and well tolerated in healthy subjects when administered alone and in combination with digoxin 0.25 mg qd.

Abstract 457: Assessment of Pharmacokinetic Drug-drug Interaction between LCZ696 and Carvedilol

Objective: LCZ696 is a first-in-class angiotensin receptor neprlysin inhibitor (ARNI) being developed for the treatment of hypertension and heart failure. Ingestion of LCZ696 results in systemic exposure to AHU377 (inactive prodrug of LBQ657, a neprilysin inhibitor) and valsartan (angiotensin receptor blocker). Carvedilol is a third-generation, non-selective beta-blocker with vasodilating properties and one of three beta-blockers with efficacy in reducing the risk of death in patients with heart failure. Since LCZ696 may be co-administered with carvedilol for optimal blood pressure control, this study was conducted to evaluate the pharmacokinetic (PK) drug-drug interaction potential between LCZ696 and carvedilol.

Methods: An open-label, three-period, single sequence study in 28 healthy subjects was conducted. In Period 1, subjects received oral LCZ696 400 mg qd x 5 days and were discharged for a 4-10 day washout. In Period 2, subjects received oral carvedilol 12.5 mg bid x first 2 days, then 25 mg bid x 4 days, and in Period 3, LCZ696 400 mg qd + carvedilol 25 mg bid x 5 days. Serial PK samples were collected and analyzed by a validated LC-MS/MS method. PK parameters (AUCtau,ss, Cmax,ss) of LCZ696 analytes(LBQ657, valsartan) and carvedilol (R(+)-and S(-)-carvedilol) in plasma were determined using non-compartmental analysis, and results were statistically evaluated.

Results: The 90% CIs of the geometric mean ratio for AUCtau,ss and Cmax,ss of LBQ657, and AUCtau,ss of valsartan fell within the range of (0.80-1.25); the lower bound for Cmax,ss of valsartan (0.88, 0.78-0.98) was below the range, indicating PK of LBQ567 was not altered but Cmax,ss of valsartan decreased by 12% when co-administered with carvedilol. Those for AUCtau,ss and Cmax,ss of both R(+)-and S(-)carvedilol fell within the range (0.80-1.25), indicating no change in PK of Carvedilol in combination with LCZ696.

Conclusion: When LCZ696 400 mg qd and carvedilol 25 mg bid were co-dministered, PK of carvedilol (R(+)-and S(-)-carvedilol) was unchanged. PK of LBQ657 or AUCtau,ss of valsartan was unchanged, while Cmax,ss decreased by 12%. LCZ696 400 mg qd was safe and well tolerated in healthy subjects when administered alone and in combination with carvedilol 25 mg bid.

Abstract 455: Assessment of Pharmacokinetic Drug-drug Interaction between LCZ696 and Hydrochlorothiazide

Objective: LCZ696 is a first-in-class angiotensin receptor neprilysin inhibitor (ARNI) being developed for the treatment of cardiovascular diseases, including hypertension and heart failure. Ingestion of LCZ696 results in systemic exposure to AHU377 (inactive prodrug of LBQ657, a neprilysin inhibitor) and valsartan (angiotensin receptor blocker). Hydrochlorothiazide (HCTZ) is indicated as first line treatment of hypertension. Since LCZ696 and HCTZ may be co-administered for optimal blood pressure control, this study was conducted to evaluate the pharmacokinetic (PK) drug-drug interaction potential between LCZ696 and HCTZ.

Methods: An open-label, three-period, single sequence study in 27 healthy subjects was conducted. In Period 1, subjects received oral HCTZ 25 mg qd x 4 days and were discharged for a 4-10 day washout. In Period 2, subjects received LCZ696 400 mg qd x 5 days, and in Period 3, HCTZ 25 mg qd + LCZ696 400 mg qd x 4 days. Serial PK samples were collected and analyzed by a validated LC-MS/MS method. PK parameters (AUCtau,ss,Cmax,ss) of LCZ696 analytes (LBQ657, valsartan) and HCTZ in plasma were determined using non-compartmental analysis, and the results were statisticallyevaluated.

Results: The 90% CIs confidence intervals (CIs) for the geometric mean ratio for AUCtau,ss of HCTZ fell within the ( 0.8 - 1.25) range, while those of Cmax,ss (0.74, 0.70-0.78) fell outside the range, indicating Cmax,ss of HCTZ decreased by 26% when co-administered with LCZ696. Those for AUCtau,ss of LBQ657 fell within the range but the upper bound for Cmax,ss (1.19, 1.10-1.28) was outside the range, indicating Cmax of LBQ657 increased by 19%; the upper bound for valsartan exposures(AUCtau,ss: 1.14, 1.00-1.29; Cmax,ss: 1.16, 0.98-1.37) were above the range, indicating AUCtau,ss and Cmax,ss of valsartan increased by 14%and 16%, respectively.

Conclusion: When LCZ696 400mg qd and HCTZ 25mg qd were co- administered, AUCtau,ss of HCTZ was unchanged but Cmax,ss decreased by 26%; AUCtau,ss of LBQ657 was unchanged but Cmax,ss increased by 19%; and lastly, AUCtau,ss and Cmax,ss of valsartan increased by 14%and 16%, respectively. LCZ696 400 mg qd was safe and well tolerated in healthy subjects when administered alone and in combination with HCTZ 25 mg qd.

Abstract 448: Assessment of Drug Interaction Potential Between LCZ696 and Warfarin

Objective: LCZ696 is a first-in-class angiotensin receptor neprilysin inhibitor (ARNI) being developed for the treatment of cardiovascular diseases including hypertension and heart failure. Ingestion of LCZ696 results in systemic exposure to AHU377 (an inactive prodrug converted to LBQ657, neprilysin inhibitor) and valsartan (angiotensin receptor inhibitor). Warfarin, a CYP2C9 substrate and narrow therapeutic index drug , is administered to patients with cardiovascular diseases including heart failure . Since LCZ696 is a known weak inhibitor of CYP2C9, the objective of this study was to determine whether LCZ696 affects the pharmacokinetics (PK) and pharmacodynamics (PD) of warfarin. Also, the warfarin effect on the PK of LCZ696 was evaluated.

Methods: This study employed an open label, single blind, two-period, crossover design in 26 healthy subjects. In each period, subjects received either 200 mg LCZ696 or matching placebo b.i.d for 10 days with a single dose of 25 mg warfarin co-administered on Day 5. Serial PK samples were collected on Day 4 and Day 5 and analyzed using validated LCMS/MS methods. Prothrombin time (PTT) and INR values were measured for up to 144 hours post warfarin dose. The PK parameters including Cmax and AUCs of LCZ696 analytes (LBQ657 and valsartan) and warfarin (R-warfarin and S-warfarin) and PD parameters of warfarin (peak PTT, peak INR, AUC-PTT, and AUC-INR) were determined using noncompartmental methods and results were statistically evaluated.

Results: The 90% confidence intervals (CI) of geometric mean ratios of Cmax and AUCs (test/reference) for R-warfarin, S-warfarin, LBQ657, and valsartan were within the 80 - 125% suggesting lack of PK interaction between LCZ696 and warfarin. Further, the 90% CI of geometric mean ratios of average (AUC effect/144) and peak PD effects (PTT and INR) were also within the 80 - 125% range indicating no impact of LCZ696 on warfarin PD.

Conclusion: Co-administration of 200 mg LCZ696 b.i.d with single dose of 25 mg warfarin did not alter the PK exposures of LCZ696 analytes (LBQ657 and valsartan) and warfarin. Also, LCZ696 did not affect the PD effects of warfarin. LCZ696 200 mg b.i.d was safe and well tolerated when administered alone or with single dose of 25 mg warfarin.

Abstract 456: Assessment of Pharmacokinetic Drug Interaction between LCZ696 and Metformin

Objective: LCZ696 is a first-in-class angiotensin receptor neprilysin inhibitor (ARNI) being developed for the treatment of cardiovascular diseases, including hypertension and heart failure. Ingestion of LCZ696 results in systemic exposure to AHU377 (inactive prodrug that is converted to LBQ657, a neprilysin inhibitor) and valsartan (angiotensin receptor blocker). Metformin is the most commonly prescribed oral treatment for type 2 diabetes mellitus (T2DM), a condition prevalent in patients with cardiovascular diseases. Since LCZ696 and metformin may be co-administered, the potential for a pharmacokinetic (PK) interaction was assessed between these drugs.

Methods: The study was conducted in 27 healthy subjects of Japanese descent using an open-label, three-period, single-sequence design. In Period 1, subjects received metformin 1000 mg once daily (q.d.) for 4 days. Following a metformin washout of 4-10 days, subjects received LCZ696 400 mg q.d. for 5 days in Period 2. In Period 3, LCZ696 400 mg q.d. and metformin 1000 mg q.d. were co-administered for 4 days. Serial PK samples were taken during all treatment periods and analyzed using validated LC/MS/MS bioanalytical techniques. The PK parameters (Cmax,ss, AUCtau,ss) of active LCZ696 analytes (LBQ657 and valsartan) and metformin were determined using non-compartmental analysis, and the results were evaluated by statistical analysis.

Results: The 90% confidence intervals for the geometric mean ratios for Cmax,ss and AUCtau,ss of LCZ696 analytes (LBQ657 and valsartan) were within the 0.8-1.25 range indicating that metformin did not affect the PK of the LCZ696 analytes. The lower bound of the 90% confidence intervals for the geometric mean ratios for metformin exposures were below the 0.8-1.25 range (Cmax,ss: 0.77, 0.70-0.84; AUCtau,ss: 0.77, 0.71-0.82), indicating a decrease in Cmax,ss and AUCtau,ss of metformin by 23%.

Conclusion: After co-administration of LCZ696 400 mg q.d. and metformin 1000 mg q.d., the exposures of LBQ657 and valsartan remained unchanged whereas the exposure to metformin decreased by 23%. LCZ696 400 mg q.d. was safe and well tolerated in healthy subjects when administered alone and in combination with metformin 1000 mg q.d..

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.

Evaluation of pharmacokinetic interactions between amlodipine, valsartan, and hydrochlorothiazide in patients with hypertension

The steady-state pharmacokinetic (PK) interaction potential between amlodipine (10 mg), valsartan (320 mg), and hydrochlorothiazide (HCTZ; 25 mg) was evaluated in patients with hypertension in a multicenter, multiple-dose, open-label, 4-cohort, parallel-group study. Eligible patients were randomly allocated to the dual combination of valsartan + HCTZ, amlodipine + valsartan, or amlodipine + HCTZ and nonrandomly allotted to amlodipine + valsartan + HCTZ triple combination treatment. After 6 days of treatment with a half-maximal dose of different combinations, patients were up-titrated to the maximal drug doses from day 7 through day 17. PK parameters of corresponding analytes from the triple- and dual-treatment groups were estimated on day 17 and compared. Safety and tolerability of all treatments was assessed. The C ( ssmax ) and AUC(0-τ) values of amlodipine or HCTZ remained unaffected when administered with valsartan + HCTZ or valsartan + amlodipine, respectively. On the other hand, valsartan exposure increased by 10% to 25% when coadministered with HCTZ and amlodipine, which is not considered clinically relevant. In conclusion, there were no clinically relevant PK interactions with amlodipine, valsartan, and HCTZ triple combination compared with the corresponding dual combinations. All treatments were safe and well tolerated.

Population pharmacokinetics of valsartan in pediatrics

The objective of this work was to develop a population pharmacokinetic model to assess the influence of subject covariates on the pharmacokinetics of valsartan in children. Data were collected from a single dose study in 26 hypertensive children ages 1 to 16 years. Subjects received 2 mg/kg valsartan suspension up to a maximum dose of 80 mg. Plasma samples were collected and analyzed using LC/MS/MS. Several structural pharmacokinetic models were evaluated for appropriateness. Allometric scaling and standard covariate analyses were performed to explain interindividual variabilities. Objective function values and goodness of fit plots were used for model selection. A posterior predictive check was used for model evaluation. A linear 2-compartment first-order elimination model with zero-order absorption and lag-time best described the disposition of valsartan. Allometric scaling and standard covariate analysis revealed that age and body size have similar influence; however, after adjustment for body size using fat free mass (FFM), the effect of increasing age was no longer significant on valsartan clearance (2% per year relative to a typical 8 year old with FFM of 30 kg). The population pharmacokinetic model reveals that increase in age has minimal influence on body size dependent clearance of valsartan in children.

Probenecid treatment enhances retinal and brain delivery of N-4-benzoylaminophenylsulfonylglycine: an anionic aldose reductase inhibitor

Anion efflux transporters are expected to minimize target tissue delivery of N-[4-(benzoylaminophenyl)sulfonyl]glycine (BAPSG), a novel carboxylic acid aldose reductase inhibitor, which exists as a monocarboxylate anion at physiological conditions. Therefore, the objective of this study was to determine whether BAPSG delivery to various eye tissues including the retina and the brain can be enhanced by probenecid, a competitive inhibitor of anion transporters. To determine the influence of probenecid on eye and brain distribution of BAPSG, probenecid was administered intraperitoneally (120 mg/kg body weight; i.p.) 20 min prior to BAPSG (50 mg/kg; i.p.) administration. Drug disposition in various eye tissues including the retina and the brain was determined at 15 min, 1, 2 and 4h after BAPSG dose in male Sprauge-Dawley rats. To determine whether probenecid alters plasma clearance of BAPSG, influence of probenecid (120 mg/kg; i.p.) on the plasma pharmacokinetics of intravenously administered BAPSG (15 mg/kg) was studied as well. Finally, the effect of probenecid co-administration on the ocular tissue distribution of BAPSG was assessed in rabbits following topical (eye drop) administration. Following pretreatment with probenecid in the rat study, retinal delivery at 1h was increased by about 11-fold (2580 ng/g vs. 244 ng/g; p<0.05). Further, following probenecid pretreatment, significant BAPSG levels were detectable in the brain (45 + or - 20 ng/g) at 1h, unlike controls where the drug was not detectable. Plasma concentrations, plasma elimination half-life, and total body clearance of intravenously administered BAPSG were not altered by i.p. probenecid pretreatment. In the topical dosing study, a significant decline in BAPSG delivery was observed in the iris-ciliary body but no significant changes were observed in other tissues of the anterior segment of the eye including tears. Thus, inhibition of anion transporters is a useful approach to elevate retinal and brain delivery of BAPSG.

Evaluation of the potential for steady-state pharmacokinetic interaction between vildagliptin and simvastatin in healthy subjects

BACKGROUND

Vildagliptin is an orally active, potent and selective inhibitor of dipeptidyl peptidase IV (DPP-4), the enzyme responsible for the degradation of incretin hormones. By enhancing prandial levels of incretin hormones, vildagliptin improves glycemic control in type 2 diabetes. Co-administration of vildagliptin and simva statin, an HMG-CoA-reductase inhibitor may be required to treat patients with diabetes and dyslipidemia. There fore, this study was conducted to determine the potential for pharmacokinetic drug-drug interaction between vildagliptin and simvastatin at steady-state.

METHODS

An open label, single center, multiple dose, three period, crossover study was conducted in 24 healthy subjects. All subjects received once daily doses of either vildagliptin 100 mg or simvastatin 80 mg or the combination for 7 days with an inter-period washout of 7 days. Plasma levels of vildagliptin, simvastatin, and its active metabolite, simvastatin beta-hydroxy acid (major active metabolite of simvastatin) were determined using validated LC/MS/MS methods. Pharmacokinetic and statistical analyses were performed using WinNonlin and SAS, respectively.

RESULTS

The 90% confidence intervals of C(max) and AUC(tau) of vildagliptin, simvastatin, and simvastatin beta-hydroxy acid were between 80 and 125% (bioequivalence range) when vildagliptin and simvastatin were admin istered alone and in combination. These data indicate that the rate and extent of absorption of vildagliptin and simvastatin were not affected when co-administered, nor was the metabolic conversion of simvastatin to its active metabolite. All treatments were safe and well tolerated in this study.

CONCLUSIONS

The pharmacokinetics of vildagliptin, simvastatin, and its active metabolite were not altered when vildagliptin and simvastatin were co-administered.

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.

Evaluation of a pharmacokinetic interaction between valsartan and simvastatin in healthy subjects

OBJECTIVE

The potential for a pharmacokinetic drug interaction between valsartan, an antihypertensive drug, and simvastatin, a lipid-lowering agent, was investigated in this study. This was an open-label, multiple-dose, randomized, three-period, cross over study in 18 healthy subjects. Each subject received one 160 mg valsartan tablet or one 40 mg simvastatin tablet or co-administration of valsartan (160 mg) and simvastatin (40 mg) tablets for 7 days, with a 7-day inter-dose washout period. The steady-state pharmacokinetics of valsartan, simvastatin beta-hydroxy acid (active metabolite of simvastatin) and simvastatin (pro-drug) were determined on day 7 of each dosing period.

RESULTS

The results were interpreted based on the point estimates and the 90% confidence intervals. These results indicated that the area under the curve of plasma concentration from 0 to 24 hours (AUC(0-24)) of valsartan, simvastatin beta-hydroxy acid and simvastatin was increased by 14%, 19%, and 23%, respectively, with the combination treatment. In addition, the maximum concentration (C(max)) of valsartan and simvastatin beta-hydroxy acid was increased by 10% and 22%, respectively, and the C(max) of simvastatin was decreased by 26% with the combination treatment. All treatments were safe and well tolerated.

CONCLUSIONS

Based on the wide therapeutic dosage ranges of valsartan and simvastatin, and the highly variable pharmacokinetics of three analytes, the observed differences in the exposure and C(max) of valsartan, simvastatin beta-hydroxy acid and simvastatin in the combination treatment are unlikely to be of clinical relevance.

Systemic and ocular pharmacokinetics of N-4-benzoylaminophenylsulfonylglycine (BAPSG), a novel aldose reductase inhibitor

To better develop N-[4-(benzoylamino)phenylsulfonyl]glycine (BAPSG), a potent and selective aldose reductase inhibitor capable of delaying the progression of ocular diabetic complications, the objective of this study was to assess its pharmacokinetics. The plasma pharmacokinetics of BASPG was assessed in male Sprague-Dawley rats following intravenous, intraperitoneal and oral routes of administration and its distribution to various tissues including those of the eye was studied following intraperitoneal administration. In addition, rat plasma protein binding of BAPSG was studied using ultracentrifugation method and its ocular tissue disposition was assessed following topical administration in rabbits. Plasma and tissue levels of BAPSG were analysed using an HPLC assay. BAPSG exhibited dose-proportionate AUC0 --> infinity (area under the plasma concentration-time curve) following both intravenous and intraperitoneal administration over the dose range (5-50 mg kg(-1)) studied and an erratic oral absorption profile with low oral bioavailability. The fraction bioavailability following oral and intraperitoneal administration was 0.06 and 0.7-1, respectively. BAPSG exhibited short plasma elimination half-lives in the range 0.5-1.5 h. BAPSG was bound to rat plasma proteins and the percent protein binding ranged from 83 to 99.8%. BAPSG was better distributed to cornea, lens and retina than to brain, following intraperitoneal administration in rats. However, the distribution was lower compared with kidney and liver. Following topical administration in rabbits, BAPSG delivery to the surface ocular tissues, cornea and conjunctiva was higher compared with intraocular tissues, aqueous humour, iris-ciliary body and lens. Thus, BAPSG was distributed to ocular tissues following systemic and topical modes of administration.

Iontophoretic in vivo transdermal delivery of beta-blockers in hairless rats and reduced skin irritation by liposomal formulation

PURPOSE

To demonstrate the in vivo transdermal delivery and establish the comparative pharmacokinetics of five beta-blockers in hairless rat.

METHODS

Intravenous dosing was initially done via jugular cannula. For iontophoretic delivery, current (0.1 mA/cm2) was applied for 2 h through a drug reservoir patch containing the beta-blocker (10 mg/ml). Blood samples were collected and analyzed by stereoselective HPLC assays. Any irritation resulting from patch application was quantified by a chromameter. Multilamellar liposomal formulation was prepared by the thin-film hydration method and converted to unilamellar liposomes by extrusion.

RESULTS

With transdermal iontophoresis, therapeutically relevant amounts of propranolol (83.78 +/- 7.4 ng/ml) were delivered within an hour and lasted for up to 4 h. Cmax (185.1 +/- 56.8 ng/ml) was reached at hour 3. A significantly higher amount (p < 0.05) of sotalol HCl was delivered compared to other beta-blockers. There was no significant difference in the S/R ratio of AUC0-t for enantiomers after both intravenous and transdermal delivery. Skin irritation was significantly reduced (p < 0.05) when a liposomal formulation of the propranolol base was used rather than the base itself.

CONCLUSIONS

The comparative pharmacokinetics of intravenous and transdermal iontophoretic delivery of five beta-blockers in hairless rats was established. It was shown that there is no stereoselective permeation.