digoxin and 1-hydroxymethylmidazolam

In this open-label study, 24 healthy volunteers received a single intravenous (IV) dose of 0.5 mg of midazolam on day 1 and a single oral dose each of 2 mg of midazolam and 0.5 mg of digoxin on day 3. Telaprevir 750 mg every 8 hours was administered from day 8 through day 23, along with a single IV dose of 0.5 mg of midazolam on day 17 and single oral doses of 2 mg of midazolam and 0.5 mg of digoxin on day 19. Midazolam, 1'-hydroxymidazolam, digoxin, and telaprevir concentrations in plasma and digoxin concentrations in urine were measured and pharmacokinetic parameters calculated. On comparing administration with versus without telaprevir, the geometric least squares mean ratios (with 90% confidence limits) for IV midazolam were 1.02 (0.80, 1.31) for maximum observed concentrations (C(max)) and 3.40 (3.04, 3.79) for area under the curve from 0 to 24 hours (AUC(0-24h)); for oral midazolam 2.86 (2.52, 3.25) for C(max) and 8.96 (7.75, 10.35) for AUC(0-24h); and for oral digoxin 1.50 (1.36, 1.65) for C(max) and 1.85 (1.70, 2.00) for area under the curve from 0 to infinity (AUC(0-∞)). Coadministration of telaprevir with oral midazolam resulted in approximately 3-fold decrease in the mean AUC(0-∞) of 1'-hydroxymidazolam. The renal clearance of digoxin was similar with or without telaprevir. Results show that telaprevir is an inhibitor of CYP3A and P-glycoprotein.

Topics: Adolescent; Adult; Antiviral Agents; Area Under Curve; ATP Binding Cassette Transporter, Subfamily B, Member 1; Cytochrome P-450 CYP3A; Cytochrome P-450 CYP3A Inhibitors; Digoxin; Drug Interactions; Female; Humans; Male; Midazolam; Middle Aged; Oligopeptides; Protease Inhibitors; Young Adult

In order to simultaneously determine in vivo P-glycoprotein (P-gp) and Cytochrome P450 3A (CYP3A) activity, a new, rapid and sensitive liquid chromatography/tandem mass spectrometry (LC-MS/MS) method has been developed and fully validated to simultaneously determine midazolam (MDZ, as CYP3A substrate), 1'-hydroxymidazolam (1'-OHMDZ) and digoxin (DG, as P-gp substrate) in rat plasma using digitoxin as the internal standard (IS). After a single step liquid-liquid extraction with tert-butyl methyl ether/dichloromethane (75:25, v/v), analytes were subjected to LC-MS/MS analysis using positive electro-spray ionization (ESI(+)) under selected reaction monitoring mode (SRM). Chromatographic separation was performed on an XTerra MS C18 column (50mm×2.1mm, i.d. 3.5μm). The MS/MS detection was conducted by monitoring the fragmentation of 326.05 → 244.00 (m/z) for MDZ, 342.02 →168.01 (m/z) for 1'-OHMDZ, 798.33 → 651.36(m/z) for DG and 782.67 → 635.24 (m/z) for IS. The method had a chromatographic running time of 3min and linear calibration curves over the concentrations of 2-400ng/mL for MDZ and 1'-OHMDZ and 0.5-100ng/mL for DG. The recoveries of the method were 86.8-96.3% for MDZ, 84.6-86.4% for 1'-OH MDZ, and 81.7-85.1% for DG. The lower limit of quantification (LLOQ) of the method was 2ng/mL for MDZ and 1'-OHMDZ and 0.5ng/mL for DG. The intra- and inter-batch precision were less than 15% for all quality control samples at concentrations of 5, 50 and 320ng/mL for MDZ and 1'-OHMDZ and 1, 10 and 80ng/mL for DG. The validated LC-MS/MS method has been successfully used to analyze the concentrations of MDZ, 1'-OH MDZ and DG in rat plasma for simultaneous measurement of in vivo P-gp and CYP 3A activity.

Topics: Animals; ATP Binding Cassette Transporter, Subfamily B, Member 1; Biotransformation; Calibration; Cardiotonic Agents; Chromatography, High Pressure Liquid; Cytochrome P-450 CYP3A; Digoxin; Drug Interactions; Drug Stability; Limit of Detection; Male; Midazolam; Random Allocation; Rats; Rats, Sprague-Dawley; Reproducibility of Results; Spectrometry, Mass, Electrospray Ionization; Tandem Mass Spectrometry

Furanocoumarins in grapefruit are known to show inhibitory effects against P-glycoprotein (P-gp) and CYP3A4 in intestinal epithelial cells; however, furanocoumarin derivatives are widely contained in the plants of Rutaceae and Umbelliferae families, which are used as components of Kampo extract medicines. In this study, we investigated the inhibitory effects of 12 furanocoumarins extracted from plants in the Umbelliferae family against P-gp and CYP3A4 activity. Furthermore, we studied their inhibitory effect on P-gp when furanocoumarins are used as Kampo extract medicine rather than as an isolated single compound. From screening of the CYP3A4 inhibitory effect, notopterol and rivulobirin A, the only dimer types of furanocoumarin, were found to be potent inhibitors of CYP3A4. On the other hand, byakangelicol and rivulobirin A showed strong P-gp inhibition from the screening of P-gp inhibitor evaluated by quinidine permeation through the Caco-2 monolayer; however, the chemical structural relationship of furanocoumarins between P-gp and CYP3A4 inhibitory effects could not be obtained. We also investigated the effect of these furanocoumarins on the transport of digoxin through the Caco-2 monolayer. The inhibitory effect of rivulobirin A was more potent than that of byakangelicol. Application of either Senkyu-cha-cho-san or Sokei-kakketsu-to, which are composed of herbal remedies in the Umbelliferae group, significantly decreased the efflux ratio of digoxin. In conclusion, it was found that some furanocoumarins extracted from the plants in the Umbelliferae family strongly inhibited P-gp and CYP3A4. Kampo extract medicines containing herbal remedies belonging to the Umbelliferae family may cause a drug-drug interaction with P-gp or a CYP3A4 substrate drug.

Topics: Anti-Arrhythmia Agents; ATP Binding Cassette Transporter, Subfamily B, Member 1; Caco-2 Cells; Cytochrome P-450 CYP3A; Cytochrome P-450 CYP3A Inhibitors; Digoxin; Furocoumarins; Humans; Medicine, Kampo; Midazolam; Quinidine