A Reference-Scaled Average Bioequivalence Study of Azithromycin Tablets Manufactured in China and the United States: An Open-Label, Randomized, Single-Dose, 3-Way Crossover Study in Healthy Chinese Subjects Under Fasted and Fed Conditions.

Azithromycin (Zithromax) is an azalide antibiotic that binds to the 50S ribosomal subunit of the susceptible organism and thereby interferes with its protein synthesis. An open-label, randomized, single-dose, 3-way crossover bioequivalence study was conducted to compare the rate and extent of absorption of the azithromycin 250-mg tablet manufactured at Pfizer Dalian (China) and that at Pfizer Barceloneta (United States) under fasted and fed conditions in healthy Chinese subjects. This study aimed to support a generic consistency evaluation program, initiated by the National Medical Products Administration, for evaluating the quality and efficacy of the products manufactured in China. In the study, the within-subject standard deviation for area under the serum concentration-time profile from time 0 to 72 hours after dosing in the fasted condition was <0.294, and the 90%CI for the ratio was within 80% to 125%; the within-subject SDs for serum peak concentration in the fasted condition, area under the serum concentration-time profile from time 0 to 72 hours after dosing in the fed condition, and serum peak concentration in the fed condition, were all >0.294, with the upper confidence bounds being <0.00, and the point estimates of the ratios being within 80% to 125%. The results support the bioequivalence between azithromycin tablets manufactured in China and the United States in fasted and fed conditions, with both tablets showing an acceptable safety/tolerability profile in the studied population.

Is it safe to take Radix Salvia Miltiorrhiza - Radix Pueraria Lobate product with warfarin and aspirin? A pilot study in healthy human subjects.

ETHNOPHARMACOLOGICAL RELEVANCE: Radix Salvia Miltiorrhiza (Danshen) and Radix Pueraria Lobate (Gegen) are officially listed in the Chinese Pharmacopoeia and have long been used together as a Compound Chinese Traditional Medicine (CCTM) for treatment of coronary heart diseases, which are often co-administered with aspirin or warfarin to patients suffering from cardiovascular diseases. AIM OF STUDY: Since significant pharmacokinetic and pharmacodynamic interactions between Danshen-Gegen (DG) formula and aspirin/warfarin have been observed in our previous rat studies, the current study was proposed aiming to further verify such pharmacokinetic and pharmacodynamic interactions in healthy human subjects and explore related mechanisms. MATERIALS AND METHODS: A 5-day, multiple dose, five-session clinical trial has been carried out (n = 14) with 2-week washout periods between sessions, during which the subjects would receive different combinations of the medications. Plasma samples were collected for pharmacokinetic evaluation, and whole blood samples were collected for pharmacodynamic evaluation. In addition, an in-vitro mechanistic study is conducted to investigate the role of danshensu on the anti-thrombotic and anti-platelet aggregation effects of warfarin and aspirin respectively. RESULTS: Significant pharmacokinetic and pharmacodynamic herb-drug interactions were observed in healthy human subjects. pharmacokinetically, co-administration of DG with aspirin or warfarin could lead to a moderately increased AUC0→t of aspirin and a decreased AUC0→t of 7-hydroxyl warfarin respectively. The systemic exposure of danshensu (DSS, the marker component of DG) would be significantly increased after co-administration with warfarin. Pharmacodynamically, a reduction in systemic thromboxane B2 concentration was noticed after administration of DG with aspirin, which could be associated with the increased systemic exposure of aspirin and the synergistic effect of danshensu, aspirin and salicylic acid on cyclooxygenase (COX) inhibition. An offset on the warfarin induced soluble thrombomodulin induction was observed after its co-administration with DG, which could be partially attributed to the COX-2 inhibition effect of danshensu. CONCLUSION: Our results indicated that co-administration of DG with aspirin/warfarin would lead to significant pharmacokinetic and pharmacodynamic herb-drug interactions in healthy human subjects.

Cytosolic ß-glucosidase inhibition and renal blood flow suppression are leading causes for the enhanced systemic exposure of salidroside in hypoxic rats.

The promising benefits of salidroside (SAL) in alleviating high altitude sickness boost investigations on its pharmacokinetics and biological activity. However, the transportation and disposition process of SAL under hypoxic conditions has never been explored. The current study was proposed to investigate the pharmacokinetics of SAL in hypoxic rats and to explore the underlying mechanisms for the distinct metabolic fate of SAL under hypoxia. Pharmacokinetic studies on SAL was conducted in both hypoxic and normoxic rats. The transport properties of SAL were investigated on both hypoxic and normoxic Caco-2 monolayer models. Enzymes involved in SAL metabolism were identified and the effects of hypoxia on these enzymes were assessed by real-time PCR, western blotting analyses, and rat liver homogenate incubation. The renal clearance (CLr) of SAL, effective renal plasma flow (ERPF) and glomerular filtration rate (GFR) in both hypoxic and normoxic rats were also determined for renal function assessment. It was found that the systemic exposure of SAL in hypoxic rats was remarkably higher than that in normoxic rats. The barrier function of Caco-2 monolayer was weakened under hypoxia due to the impaired brush border microvilli and decreased expression of tight junction protein. Hepatic metabolism of SAL in hypoxic rats was attenuated due to the reduced activity of cytosolic ß-glucosidase (CBG). Moreover, CLr of SAL was reduced in hypoxic rats due to the suppressed ERPF. Our findings suggest the potential need for dose-adjustment of SAL or its structural analogs under hypoxic conditions.

Puerarin offsets the anticoagulation effect of warfarin in rats by inducing rCyps, upregulating vitamin K epoxide reductase and inhibiting thrombomodulin.

PURPOSE: The current study was conducted to investigate the potential pharmacokinetic and pharmacodynamic interactions between warfarin and puerarin which is the most abundant component in Pueraria lobata (Gegen). In vivo and ex vivo rat models were used to reveal the underlying mechanisms of such interactions. METHODS: Apart from one control group, five groups of Sprague-Dawley rats were treated with warfarin, oral puerarin, oral puerarin with warfarin, intravenous puerarin, intravenous puerarin with warfarin. The treatment lasted for 5 consecutive days. Thereafter, the levels of warfarin, warfarin metabolites and puerarin in plasma of these rats were monitored and compared. The rCyps activity and expression in rat livers of different treatment groups were assessed. The prothrombin time was observed. The vitamin K epoxide reductase (VKOR) activity and expression in rat livers were evaluated. Thrombomodulin activity and expression in the rat lung and rat plasma were assessed. The soluble thrombomodulin (sTM) concentrations of different treatment groups were examined. RESULTS: Intravenously administered puerarin altered the pharmacokinetics of warfarin significantly by shortening t1/2 , decreasing AUC0-96 h and increasing the clearance of warfarin. Further mechanistic studies suggested that both oral and intravenous administration of puerarin significantly induced the activities and expressions of rCyp2b1, rCyp2c6 and rCyp1a1. In addition, co-administration of puerarin reduced the prothrombin time of rat plasma by enhancing VKOR and inhibiting thrombomodulin. CONCLUSION: Puerarin increased warfarin metabolism and offset warfarin anticoagulation by inducing rCyps, upregulating VKOR and inhibiting thrombomodulin in rats. The clinical impact of such potential interactions warrants further verification. Copyright © 2016 John Wiley & Sons, Ltd.

Comparison of Pharmacokinetics and Tissue Distribution Kinetics of Roxithromycin and Expression of CYP 3A1 between Pregnant Mice and Foetuses.

The roxithromycin, macrolide antibiotics, is recommended for treating mycoplasma infection and has the potential to be administered to pregnant women who are susceptible to the infection. This study compared the pharmacokinetic properties and tissue distribution of roxithromycin among pregnant mice and their foetuses. We also determined the level of CYP3A1, a major enzyme for roxithromycin metabolism, in liver microsomes and investigated the placental transport properties of roxithromycin. Biosamples were collected from female mice at gestational day 17 after a single intragastric administration of roxithromycin. A sensitive and specific liquid chromatography-tandem mass spectroscopy method was developed to detect the drug concentration and to obtain kinetic data. The level of CYP3A1 was significantly lower in foetal liver compared with that in maternal liver according to Western blot data, suggesting a decreased metabolism and prolonged half-life of roxithromycin in the foetus. The tissue distributions of roxithromycin were similar between mother and foetus, indicating that the placental barrier did not block the transport of roxithromycin from mother to foetus. The current findings are consistent with the clinical efficacy of roxithromycin in both pregnant mothers and foetuses. Based on this study, it is feasible and reasonable to predict the transport properties of other lipophilic drugs during pregnancy.

Mechanistic study on the pharmacokinetic process of salidroside in hypoxic rats / 中国药理学与毒理学杂志

OBJECTIVE To investigate the effect of hypoxia on the pharmacokinetic process of salidrosidein rats and to explore its underlying mechanisms. METHODS The Caco-2 cell monolayerwas exposed to 1% oxygen (O2) concentration for 24 h to build the hypoxiccell model. The transportation mode of salidroside was investigated with the aid of this hypoxia model by detecting the apparent permeability coefficient(Papp). Healthy Sprague Dawley (SD) rats were exposed to 9% O2 for 72 h for the construction of hypoxic rat model. Liver sample was subsequently collected from the hypoxic rats with an aim to identify enzymes responsible for salidroside metabolism. The expression levels of sali?droside-transporting and salidroside-metabolizing enzymes, including Sodium-dependent glucose cotrans?porters (SGLT1), β-glucosidase (GBA3)and sulfotransferase (SULT2A1), were thereafter detected by RT-PCR and Western blot. The metabolic activity of GBA3 and SULT2A1 was monitored by rat liver microsome incubation.In addition, the renal function of rats under hypoxia was assessed by detecting concentrations of blood urea nitrogen and creatinine. RESULTS The AUC and t1/2 values of salidroside in hypoxic rats were more than doubled, while the in vivo clearance was significantly reduced. Mechanistic study demonstrated that the PappA- B/PappB- A eualsto 10.3, indicating the potential active transport of salidrosile. The expression of SGLT1 and GBA3 was significantly decreased, which indicated a reduced metabolism of salidroside under hypoxia. Moreover, rat under hypoxia was found to suffer from renal dysfunction, with an abnormal value of blood urea nitrogen. CONCLUSION Due to the reduced metabolism and the abnormal renal function under hypoxia, the systemic exposure of salidroside in rats was signifi?cantly enhanced.

Glucuronidation is the dominating in-vivo metabolism pathway of herbacetin:elucidation of herbacetin pharmacokinetics after intravenous and oral administration in rats / 中国药理学与毒理学杂志

OBJECTIVE To map a comprehensive metabolic pathway of herbacetin in rats, specifically, to elucidate the biotransformation of herbacetin in vivo and to simultaneously monitor the pharmacokinetic process of both parent drug and its major metabolites. METHODS liquid chromatography/ion trap mass spectrometry (LC/MSn) and ultra-liquid chromatography coupled with mass spectrometry (UPLC/MS) were combined in the current study for qualitative and quantitative determinations of herbacetin and its metabolites in bile, urine and feces after both oral and intravenous administration of herbacetin to rats. Enzyme kinetic studies on the intestinal and hepatic metabolism of herbacetin were further conducted to elucidate metabolic profiles of herbacetin in rat tissues and organs. Additionally, plasma concentration profiles of herbacetin and its metabolites in rats were obtained to characterize the overall pharmacokinetic behavior of herbacetin. RESULTS It was found that herbacetin was excreted primarily from rat urine in the form of glucuronide-conjugations. Subsequent in vitro enzyme kinetic studies and in vivo pharmacokinetic investigations suggested an extensive hepatic metabolism of herbacetin and the high exposure of herbacetin- glucuronides in systemic circulation. The clearance, half- life and bioavailability of herbacetin in rats were determined as (16.4±1.92)mL·kg-1·min-1, (11.9±2.7)min, and 1.32%, respectively. On basis of these findings, a comprehensive metabolic pathway of herbacetin in rats was composed. In addition, a physiology based pharmacokinetic (PBPK) model was successfully developed with the aid of the GastroPlus to simulate the pharmacokinetic process of herbacetin in rats. Application of the PBPK modeling can provide a useful starting point to understand and extrapolate pharmacokinetic parameters among different species, populations, and disease states. CONCLUSION After oral administration, herbacetin was subjected to colonic degradation and extensive first pass metabolism, with glucuronidation as its dominating in vivo metabolic pathway.

Enhancement of Exposure and Reduction of Elimination for Paeoniflorin or Albiflorin via Co-Administration with Total Peony Glucosides and Hypoxic Pharmacokinetics Comparison.

There is evidence suggesting that herbal extracts demonstrate greater bioactivities than their isolated constituents at an equivalent dose. This phenomenon could be attributed to the absence of interacting substances present in the extracts. By measuring the pharmacokinetic parameters of paeoniflorin (PF) and albiflorin (AF) after being orally administered to rats in isolated form, in combination with each other and within total peony glucosides (TPG), respectively, the current study aimed to identify positive pharmacokinetic interactions between components of peony radix extracts. Moreover, the pharmacokinetic profiles of PF and AF under normoxia and hypoxia were also investigated and compared. In order to achieve these goals, a highly sensitive and reproducible ultra-peformance liquid chromatography-mass spectrometry (UPLC-MS) method was developed and validated for simultaneously quantitation of PF and AF in rat plasma. This study found that compared with that of single component (PF/AF), the exposure of PF in rat plasma after combination administration or TPG administration was significantly increased, meanwhile the elimination of PF/AF was remarkably reduced. It was also noticed that AUC and Cmax of PF in hypoxia rats were significantly decreased compared with that of normaxia rats, suggesting that there was a decreased exposure of PF in rats under hypoxia. The current study, for the first time, revealed the pharmacokinetic interactions between PF/AF and other constitutes in TGP and the pharmacokinetic profiles of PF and AF under hypoxia. In view of the current findings, it could be supposed that the clinical performance of total peony glucosides would be better than that of single constitute (PF/AF). The outcomes of this animal study are expected to serve as a basis for development of clinical guidelines on total peony glucosides usage.

Radix Puerariae lobatae (Gegen) suppresses the anticoagulation effect of warfarin: a pharmacokinetic and pharmacodynamics study.

BACKGROUND: Radix Salvia miltiorrhiza (Danshen) and Radix Puerariae lobatae (Gegen) are used in Traditional Chinese Medicine to treat cardiovascular diseases. However, adverse herb-drug interactions were observed between warfarin and herbal remedies containing Danshen and Gegen. This study aims to investigate the pharmacokinetic and pharmacodynamic interactions between warfarin and the different components found in Danshen and Gegen. METHODS: Sixty Sprague-Dawley rats were used to investigate the effects of warfarin (0.2 mg/kg), Danshen (240 or 480 mg/kg) and Gegen (240 or 480 mg/kg) both in isolation and combination. The rats in the warfarin and Danshen/Gegen combination groups were given an oral dose of Danshen or Gegen 2 h after being given an oral dose of warfarin. After five consecutive days of treatment, the pharmacokinetic interactions between Danshen/Gegen and warfarin were investigated by simultaneously monitoring and comparing the cytochrome P450 (CYP) activities, mRNA and protein expression levels in the livers of the rats from the different treatment groups. The pharmacodynamic interactions were evaluated by monitoring and comparing the vitamin K epoxide reductase (VKOR) activities, mRNA and protein expression levels in the livers of rats from the different groups, as well as the thrombomodulin (TM) activities, mRNA and protein in the lungs of these animals. The rat plasma soluble thrombomodulin concentrations of the different treatment groups were also evaluated. Microsomes incubation, Real Time-Polymerase Chain Reaction and Western blot was applied respectively to study the activity, mRNA expression and protein expression of CYP, VKOR and TM. RESULTS: The activities and expression levels of the CYP and VKOR enzymes in the warfarin-Gegen combination groups increased by nearly 30 % (P = 0.02) compared with the warfarin-alone group, whereas those of TM decreased by almost 25 % (P = 0.02). The administration of Danshen did not lead to any changes in the activities or the expression levels of the CYP, VKOR or TM enzymes compared with those of the control group. Gegen induced several warfarin-metabolizing CYP enzymes and neutralized the effects of warfarin towards VKOR and TM. CONCLUSION: Gegen, rather than Danshen at the same tested dosage, offsets the anticoagulant effects of warfarin by accelerating the phase I liver metabolism of warfarin, as well as increasing the activity, mRNA and protein expression of VKOR while decreasing those of TM.

Induction of liver cytochrome P450s by Danshen-Gegen formula is the leading cause for its pharmacokinetic interactions with warfarin.

ETHNOPHARMACOLOGICAL RELEVANCE: Although the increased usage of herbal medicine leading to herb-drug interactions is well reported, the mechanism of such interactions between herbal medicines with conventionally prescribed drugs such as warfarin is not yet fully understood. Our previous rat in vivo study demonstrated that co-administration of Danshen-Gegen Formula (DGF), a Radix Salvia miltiorrhiza (Danshen) and Radix Puerariae lobatae (Gegen) containing Chinese medicine formula recently developed for the treatment of cardiovascular disease, with warfarin could cause significant herb-drug interactions. The current study aims to explore the pharmacokinetics-based mechanism of the DGF-warfarin interactions during absorption, distribution and metabolism processes. MATERIALS AND METHODS: Caco-2 cell monolayer model and rat in situ intestinal perfusion model were used to study the DGF-warfarin interactions during the intestinal absorption processes. Male Sprague-Dawley rats were orally administered warfarin in presence and absence of DGF for consecutive 5 days. The microsomal activity and expression of the liver CYP isozymes were determined and compared among different treatment groups. Blood from the rats administered DGF was employed to evaluate effects of DGF on the plasma protein binding of warfarin. RESULTS: Absorption studies demonstrated that DGF could potentially increase the intestinal absorption of warfarin (32% and 75% increase of warfarin Papp in Caco-2 and intestinal perfusion models, respectively) via altering the regional pH environment in GI tract. DGF administration could lead to significant increase in liver microsomal activity and mRNA expression of CYP1A1 and CYP2B1, indicating the potential induction on the liver metabolism of warfarin by DGF. Moreover, it has been proven by ex vivo study that the single-dose administration of DGF could decrease the protein binding of warfarin in plasma by at least 11.6%. CONCLUSION: Collectively, current study demonstrated that DGF could significantly induce the liver phase I metabolism of warfarin, and to a less extent, potentially increase the intestinal absorption and decrease the plasma protein binding of warfarin. The inductive effects of DGF on the liver phase I metabolism of warfarin may be dominantly responsible for the DGF-warfarin pharmacokinetics interactions.

Updates on the clinical evidenced herb-warfarin interactions.

Increasing and inadvertent use of herbs makes herb-drug interactions a focus of research. Concomitant use of warfarin, a highly efficacious oral anticoagulant, and herbs causes major safety concerns due to the narrow therapeutic window of warfarin. This paper presents an update overview of clinical findings regarding herb-warfarin interaction, highlighting clinical outcomes, severity of documented interactions, and quality of clinical evidence. Among thirty-eight herbs, Cannabis, Chamomile, Cranberry, Garlic, Ginkgo, Grapefruit, Lycium, Red clover, and St. John's wort were evaluated to have major severity interaction with warfarin. Herbs were also classified on account of the likelihood of their supporting evidences for interaction. Four herbs were considered as highly probable to interact with warfarin (level I), three were estimated as probable (level II), and ten and twenty-one were possible (level III) and doubtful (level IV), respectively. The general mechanism of herb-warfarin interaction almost remains unknown, yet several pharmacokinetic and pharmacodynamic factors were estimated to influence the effectiveness of warfarin. Based on limited literature and information reported, we identified corresponding mechanisms of interactions for a small amount of "interacting herbs." In summary, herb-warfarin interaction, especially the clinical effects of herbs on warfarin therapy should be further investigated through multicenter studies with larger sample sizes.