Liver-to-plasma vaniprevir (MK-7009) concentration ratios in HCV-infected patients.

BACKGROUND: Some drugs that are actively taken up into the liver exhibit greater than dose proportional increases in plasma exposure, although human liver-to-plasma concentration ratios have rarely been evaluated. Understanding these relationships has implications for drug concentrations at the target site for certain classes of compounds, such as direct-acting antivirals, targeted towards HCV. METHODS: Treatment-experienced, chronic HCV non-cirrhotic patients (n=3) received vaniprevir (600 mg or 300 mg twice daily) on days 1-3 and (600 mg or 300 mg single dose) on day 4. Core needle biopsy was performed at 6 or 12 h post-dose on day 4. Blood samples were collected pre-dose on days 1 and 4, and for 24 h post-dose on day 4. The primary study objective was the hepatic concentration of vaniprevir at 6 and 12 h post-dose. RESULTS: Vaniprevir plasma pharmacokinetic parameters increased in a greater than dose-proportional manner between the 300 mg and 600 mg doses, with approximately fivefold increases in AUC0-12 and Cmax associated with a twofold increase in dose (AUC0-12, 10.6 µM/h to 59.5 µM/h; Cmax, 2.60 µM to 13.5 µM). In the 300 mg and 600 mg dose groups, mean liver concentrations of vaniprevir were 84.6 µM and 169 µM at 6 h post-dose, and 29.4 µM and 53.7 µM at 12 h post-dose. Liver concentrations were higher than plasma with liver-to-plasma concentration ratios of approximately 20-280. CONCLUSIONS: These data confirm higher vaniprevir concentrations in human liver compared with plasma and demonstrate that measurement of human liver drug concentration using needle biopsy is feasible.

Bioequivalence of Alendronate and Vitamin D3 in a Combination Tablet Versus Corresponding-Dose Individual Tablets in Healthy Taiwanese Volunteers, Determined Using a Novel Plasma Alendronate Assay.

OBJECTIVE: This study was designed to demonstrate that alendronate (ALN)/vitamin D3 combination tablets (ALN/D5600) are bioequivalent to corresponding doses of ALN and vitamin D3 as individual tablets in healthy Taiwanese volunteers. METHODS: In this open-label, randomized, 2-period, crossover study, 68 volunteers were randomized to a single ALN/D5600 combination tablet or corresponding doses of 70 mg ALN + 5600 IU vitamin D3 (2 × 2800 IU), followed by a 12-day washout period and administration of the alternate formulation. Plasma ALN levels were measured using a newly developed assay. Geometric mean ratios of ALN AUC0-last, AUC0-∞, and Cmax, and unadjusted vitamin D3 AUC0-80h and Cmax were compared and considered bioequivalent if the 90% CI was within 0.8 to 1.25. RESULTS: The geometric mean ratios were: AUC0-last, 1.084 (90% CI, 0.937-1.253); AUC0-∞, 1.081 (90% CI, 0.935-1.249); and Cmax, 1.112 (90% CI, 0.959-1.289) for ALN, and AUC0-80h 0.953 (90% CI, 0.827-1.098) and Cmax, 0.982 (90% CI, 0.854-1.130) for vitamin D3 unadjusted for endogenous levels. CONCLUSIONS: The combination tablet was considered bioequivalent to coadministration based on ALN AUC0-∞ and unadjusted vitamin D3 parameters. Slight differences for ALN AUC0-last and Cmax (upper 90% CIs outside the bounds) were not considered clinically significant. The combination tablet was well tolerated. No serious adverse experiences were reported. © 2015. The Authors. Published by Elsevier Inc. All rights reserved.

Pharmacokinetic-pharmacodynamic studies of the 11ß-hydroxysteroid dehydrogenase type 1 inhibitor MK-0916 in healthy subjects.

AIMS: To characterize pharmacokinetic parameters of MK-0916 and its safety and tolerability in lean, healthy male subjects following single and multiple oral doses. To assess (by stable-isotope labelling) the in vivo inhibition of cortisone-to-cortisol conversion following oral MK-0916. METHODS: Data are presented from two randomized, controlled, double-blind, rising-dose phase I studies. In the first study, subjects received single oral doses of 0.4-100 mg MK-0916 (n = 16). In the second study, subjects received 0.2-225 mg MK-0916 followed by daily doses of 0.2-100 mg for 13 days beginning on day 2 or day 15 (n = 80). Plasma and urine drug concentrations were measured for pharmacokinetic analysis. For pharmacodynamic analysis, concentrations of plasma [(13)C4]cortisol were measured by high-pressure liquid chromatography and tandem mass spectrometry following a single oral dose of 5 mg [(13)C4]cortisone. RESULTS: Doses ≥3 mg were rapidly absorbed (time at which maximal concentration was achieved in plasma, 1.1-1.8 h). Exposure (measured as the area under the concentration-time curve from 0 to 168 h) increased approximately in proportion to dose. Values for the maximal plasma concentration and the plasma concentration at 24 h increased in excess of dose proportionality at doses <6 mg and roughly in proportion to dose at doses >6 mg. In subjects dosed with 6 mg MK-0916 once daily for 14 days, the mean trough plasma concentration was 240 nm and in vivo cortisone-to-cortisol conversion was inhibited by 84%. The relationship between plasma MK-0916 and hepatic 11ß-hydroxysteroid dehydrogenase type 1 inhibition was well represented by a simple Emax model with an IC50 of 70.4 nm. Exposure to MK-0916 was generally well tolerated. CONCLUSIONS: These findings indicate that 11ß-hydroxysteroid dehydrogenase type 1 is effectively inhibited in human subjects by doses of MK-0916 that are well tolerated.

Multiple doses of sitagliptin, a selective DPP-4 inhibitor, do not meaningfully alter pharmacokinetics and pharmacodynamics of warfarin.

Sitagliptin is an orally active, highly selective dipeptidyl peptidase IV (DPP-4) inhibitor for treatment of type 2 diabetes mellitus. This randomized, open-label, 2-part, 2-period crossover study assessed pharmacokinetics/pharmacodynamics of warfarin in the presence/absence of multiple-dose sitagliptin. Twelve participants received treatments A and B separated by >7-day washout: treatment A involved coadministration of sitagliptin 200 mg/d for 11 days (days 1-11) and warfarin 30 mg on day 5, and treatment B involved warfarin 30 mg alone on day 1. R(+) warfarin, S(-) warfarin, and international normalized ratio (INR) were assayed predose and up to 168 hours postdose. The geometric mean ratios (GMRs; warfarin + sitagliptin/warfarin alone) (90% confidence intervals [CIs]) were 0.99 (0.95, 1.03) and 0.95 (0.90, 1.02) for the AUC(0-infinity) of R(+) and S(-) warfarin, respectively. GMRs (warfarin + sitagliptin/warfarin alone) (90% CIs) were 0.89 (0.86, 0.93) and 0.89 (0.86, 0.92) for the C(max) of R(+) and S(-) warfarin, respectively. INR AUC(0-168 h) and INR(max) GMRs were 1.01 (0.96, 1.06) and 1.08 (1.00, 1.17), respectively. Coadministration of sitagliptin and warfarin was generally well tolerated. Pharmacokinetics (AUC for R(+) and S(-) warfarin) and pharmacodynamics (INR of R(+) or S(-) warfarin) were not meaningfully altered following coadministration of multiple-dose sitagliptin and single-dose warfarin, indicating that no dosage adjustment for warfarin is necessary when coadministered with sitagliptin.

Expression of prostaglandin D synthase and the prostaglandin D2 receptors DP and CRTH2 in human nasal mucosa.

BACKGROUND: Prostaglandin D2 (PGD2) is released from mast cells during the allergic response. OBJECTIVE: Since PGD2 has been shown to induce nasal congestion in humans, we investigated the distribution of hematopoietic prostaglandin D synthase (PGDS) and the two PGD2 receptors, DP and CRTH2 in human nasal mucosa from healthy subjects and subjects suffering from polyposis, a severe form of chronic rhinosinusitis. METHODS: DP mRNA expression was detected by in situ hybridization while PGDS, CRTH2 and various leukocyte markers expression were revealed by immunohistochemistry. RESULTS: In the normal mucosa, PGDS was only detected in few resident mast cells while CRTH2 was undetectable. In contrast, DP receptor mRNA was detected in epithelial goblet cells, serous glands and in the vasculature. In the nasal mucosa of subjects suffering from polyposis: (1) PGDS was detected in mast cells and other large infiltrating inflammatory cells, (2) both DP mRNA and CRTH2 were detected in eosinophils and (3) CRTH2 was detected on a subset of infiltrating T cells. Although DP mRNA could not be detected in the T cells invading the nasal mucosa, it was found to be expressed in the T cells present in the lymph node and the thymus from normal individuals. CONCLUSION: This study indicates that cells capable of producing PGD2 are present in the nasal mucosa and that both PGD2 receptors, DP and CRTH2, might play a role in inflammatory disease of the upper airways.