Development of a UPLC-MS/MS method for the simultaneous determination of atorvastatin, 2-hydroxy atorvastatin, and naringenin in rat plasma and its application to pharmacokinetic interaction studies.

Recent studies have revealed that the combination therapy of atorvastatin (ATV) with naringenin (NG) can offer meaningful benefits in the treatment of hypercholesterolemia, while decreasing adverse side effects. To investigate whether there are pharmacokinetic interactions among ATV, its metabolite 2-hydroxy atorvastatin (2-ATV), and NG, in the current study, we developed and validated a simple, rapid, and specific UPLC-MS/MS method to simultaneously determine the concentrations of these analytes in the rat plasma. Sample preparation was performed using simple protein precipitation. Chromatographic analysis was carried out on an Acquity UPLC BEH C18 column (1.7 µm, 2.1 × 100 mm) using gradient elution mode, and these three analytes were detected using a Xevo® TQD triple quadrupole tandem mass spectrometer, in the positive ion electrospray ionization interface. The developed method showed good linearity over the following concentrations in rat plasma samples: 3-1200 ng/ml (r = 0.9965) for ATV, 1.5-600 ng/ml (r = 0.9934) for 2-ATV, and 3-1200 ng/ml (r = 0.9964) for NG. The assays were validated and satisfied the acceptance criteria recommended by U.S. Food and Drug Administration guidelines. Upon successful application of the method to a pharmacokinetic interaction study, the results indicated that NG significantly enhanced the bioavailability of ATV and 2-ATV.

No Interference of H9 Extract on Trastuzumab Pharmacokinetics in Their Combinations.

Trastuzumab is used to treat breast cancer patients overexpressing human epidermal growth factor receptor 2, but resistance and toxicity limit its uses, leading to attention to trastuzumab combinations. Recently, the synergistic effect of trastuzumab and H9 extract (H9) combination against breast cancer has been reported. Because drug exposure determines its efficacy and toxicity, the question of whether H9 changes trastuzumab exposure in the body has been raised. Therefore, this study aimed to characterize trastuzumab pharmacokinetics and elucidate the effect of H9 on trastuzumab pharmacokinetics at a combination dose that shows synergism in mice. As a result, trastuzumab showed linear pharmacokinetics after its intravenous administration from 1 to 10 mg/kg. In the combination of trastuzumab and H9, single and 2-week treatments of oral H9 (500 mg/kg) did not influence trastuzumab pharmacokinetics. In the multiple-combination treatments of trastuzumab and H9 showing their synergistic effect (3 weeks of trastuzumab with 2 weeks of H9), the pharmacokinetic profile of trastuzumab was comparable to that of 3 weeks of trastuzumab alone. In tissue distribution, the tissue to plasma ratios of trastuzumab below 1.0 indicated its limited distributions within the tissues, and these patterns were unaffected by H9. These results suggest that the systemic and local exposures of trastuzumab are unchanged by single and multiple-combination treatments of H9.

Epicatechin exerts dual action to shield sickling and hydroxyurea-induced myelosuppression: Implication in sickle cell anemia management.

Hydroxyurea (HU) is the key drug to treat Sickle cell anemia (SCA). However, its treatment is associated with the liability of myelosuppression. The present study aimed to investigate the potential of epicatechin as a supplementation therapy for the symptomatic management of SCA under HU therapy. A panel of experiments were performed at first to observe epicatechin's effect on sickling and hemolytic behaviour using SCA patient's blood (ex vivo). Thereafter, the effect of HU in the presence or absence of epicatechin was investigated on cytokine inhibition in rat splenocytes (ex vivo) as well as alterations in hematological parameters and kidney function tests in rats (in vivo). Then, any effect of epicatechin on pharmacokinetic modulation of HU in rats was elucidated along with the underlying mechanism using a battery of in vitro and in vivo models. Epicatechin exhibited potent action on anti-sickling, polymerization inhibition, and erythrocyte membrane stability. It did not show any inherent hemolytic activity and reduced TNF-α level during concomitant administration with HU. Based on hematological changes in rats, epicatechin treatment aided to the beneficial effect of HU and prevented the treatment-linked disadvantageous effects of HU like neutropenia. The plasma exposure of HU was significantly augmented in rats upon simultaneous oral administration of epicatechin with HU. Down-regulation of Oatp1b2 and catalase possibly contributed to the pharmacokinetic interaction of HU. Epicatechin is found to be a promising candidate and should be explored at a reduced dose level of HU towards offsetting the dose-dependent myelosuppressive effect of HU under the frame of supplementation therapy in SCA.

Cytochrome P450 3A4-mediated pharmacokinetic interaction study between tadalafil and canagliflozin using high-performance thin-layer chromatography.

Diabetes is a known risk factor for sexual dysfunction in men; diabetic men have an increased risk of erectile dysfunction compared to non-diabetic men. Canagliflozin is one of the common antidiabetic drugs that is readily used in the treatment of type-2 diabetes. Concomitantly phosphodiesterase 5 inhibitors, such as tadalafil, can be given to the patient to alleviate erectile dysfunction. Canagliflozin is reported to be one of the cytochrome P450 3A4 enzyme inhibitors, that might seriously influence blood concentration levels of tadalafil but there is no study till now, discussing this interaction. Therefore, a fast, simple, and sensitive high-performance thin-layer chromatographic method was developed, validated, and applied for the simultaneous determination of tadalafil and canagliflozin in spiked and real human plasma. The limit of detection for tadalafil was 0.14 ng/band and for canagliflozin was 0.16 ng/band. The limit of quantitation value for tadalafil was 0.43 ng/band and for canagliflozin was 0.47 ng/band. Tadalafil and canagliflozin were determined simultaneously in real human plasma using the described procedure and the method was applied for in vivo pharmacokinetic drug interaction study between the studied drugs, which proved significant interaction between them when administered simultaneously.

P-glycoprotein mediates the pharmacokinetic interaction of olanzapine with fluoxetine in rats.

Clinical trials of olanzapine combined with fluoxetine (Olanzapine/Fluoxetine Combination, OFC) in the treatment of refractory depression have shown significant efficacy, but the drug-drug interaction (DDI) between them remains unclear. In this report, the pharmacokinetic interaction between olanzapine and fluoxetine was studied in wild-type (WT) and Mdr1a/b gene knockout (KO) rats. By analyzing the pharmacokinetics and tissue distribution of olanzapine in single dose and combination, the potential DDI mediated by P-gp was explored. The results showed that in WT rats, the combination of fluoxetine increased the peak concentration (Cmax, 44.1 ± 5.1 ng/mL in the combination group vs 9.0 ± 1.5 ng/mL in the monotherapy group) and the exposure (AUC0-t, 235.8 ± 22.7 h × ng/mL in the combination group vs 47.5 ± 8.4 h × ng/mL in monotherapy group) of olanzapine, and decreased the clearance (CL, 8119.0 ± 677.9 mL/h/kg in the combination group vs 49,469.0 ± 10,306.0 mL/h/kg in monotherapy group). At the same time, fluoxetine significantly increased the in vivo exposure of olanzapine in brain, liver, kidney and ileum of WT rats, indicating the occurrence of DDI. The same phenomenon was observed in Caco-2 cells in vitro as well. However, in KO rats, there was no significant difference in pharmacokinetic parameters between the monotherapy group and the combination group. In conclusion, P-gp plays an important role in the pharmacokinetic interaction between olanzapine and fluoxetine in rats. This study may provide a reference for the clinical safety of olanzapine combined with fluoxetine.

Pharmacokinetic interaction between atorvastatin and fixed-dose combination of sofosbuvir/ledipasvir in healthy male Egyptian volunteers.

PURPOSE: Comorbid conditions of heart and liver disorders added to HCV-induced hepatic steatosis make co-administration of statins, and direct-acting antivirals is common in clinical practice. This study aimed to evaluate the pharmacokinetic interaction of atorvastatin and fixed-dose combination of sofosbuvir/ledipasvir "FDCSL" with rationalization to the underlying mechanism. METHODS: A randomized, three-phase crossover study that involves 12 healthy volunteers was performed. Participants received a single-dose of atorvastatin 80 mg alone, atorvastatin 80-mg plus tablets containing 400/90 mg FDCSL, or tablets containing 400/90 mg FDCSL alone. Plasma samples were analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) for atorvastatin, sofosbuvir, ledipasvir, and sofosbuvir metabolite "GS-331007," and their pharmacokinetics parameters were determined. RESULTS: Compared to atorvastatin alone, the administration of FDCSL caused a significant increase in both areas under the concentration-time curve from time zero to infinity (AUC0-∞) and maximum plasma concentration (Cmax) of atorvastatin by 65.5% and 156.0%, respectively. Also, atorvastatin caused a significant increase in the AUC0-∞ and Cmax of sofosbuvir by 32.0% and 11.0%, respectively. Similarly, AUC0-∞ and Cmax of sofosbuvir metabolite significantly increased by 84.0% and 74.0%, respectively. However, ledipasvir AUC0-∞ showed no significant change after atorvastatin intake. The elimination rate in all drugs revealed no significant changes. CONCLUSION: After concurrent administration of FDCSL with atorvastatin, the AUC0-∞ of both atorvastatin and sofosbuvir were increased. Caution should be taken with close monitoring for possible side effects after co-administration of atorvastatin and FDCSL in clinical practice.

Amalgamation of in-silico, in-vitro and in-vivo approach to establish glabridin as a potential CYP2E1 inhibitor.

CYP2E1 is directly or indirectly involved in the metabolism of ethanol and endogenous fatty acids but it plays a major role in the bio-activation of toxic substances that produce reactive metabolites leading to hepatotoxicity. Therefore, identification of CYP2E1 inhibitor from bioflavonoids class having useful pharmacological properties has dual benefit regarding avoidance of severe food-drug/nutraceutical-drug interaction and scope to develop a phytotherapeutics through an intended pharmacokinetic interaction.In the present study, we aimed to identify CYP2E1 inhibitor from experimental bioflavonoids which are unexplored for CYP2E1 inhibition till date using in-silico, in-vitro and in-vivo approaches.Results of in-vitro CYP2E1 inhibitory studies using CYP2E1-mediated chlorzoxazone 6-hydroxylation in human liver microsomes showed that glabridin have the highest potential than fisetin, epicatechin, nobiletin, and chrysin to inhibit CYP2E1 enzyme. Mechanistic investigations indicate that glabridin is a competitive CYP2E1 inhibitor. Molecular docking study results demonstrate that glabridin strongly interacted with the active site of human CYP2E1 enzyme. Pharmacokinetics of a CYP2E1 substrate in mice model indicates a significant alteration of chlorzoxazone and 6-hydroxychlorzoxazone plasma levels in the presence of glabridin. Further studies are needed to confirm the results at clinical level.Overall, glabridin is found to be a potential CYP2E1 inhibitor.

Significant interaction between high-dose methotrexate and high-dose piperacillin-tazobactam causing reversible neurotoxicity and renal failure in an osteosarcoma patient.

INTRODUCTION: Pharmacokinetic interaction of high-dose methotrexate (MTX) and other concomitantly administered renally secreted medicinal products may lead to insufficient methotrexate serum level decrease and significant MTX toxicity. CASE REPORT: We report the case of an 18-year-old male patient treated with high-dose MTX for an osteosarcoma and with high-dose piperacillin-tazobactam at the same time. MTX serum levels were severely elevated 24 hours after the MTX infusion and did not decrease in accordance with the specific calcium folinate rescue protocol. The patient experienced renal failure accompanied by neurological symptoms, most consistent with MTX-related renal and CNS toxicity.Management and outcome: After discontinuation of piperacillin-tazobactam, intensified calcium folinate rescue therapy, and IV hydration, the MTX serum levels decreased appropriately, and toxicity symptoms resolved. DISCUSSION: Severe MTX-related toxicity, caused by drug-drug interaction, suggests that the concomitant use of high-dose MTX and high-dose piperacillin-tazobactam should be avoided generally.

Effect of Water Extract of Mangosteen Pericarp on Donepezil Pharmacokinetics in Mice.

The pharmacokinetic (PK) change in a drug by co-administered herbal products can alter the efficacy and toxicity. In the circumstances that herb-drug combinations have been increasingly attempted to alleviate Alzheimer's disease (AD), the PK evaluation of herb-drug interaction (HDI) is necessary. The change in systemic exposure as well as target tissue distribution of the drug have been issued in HDIs. Recently, the memory-enhancing effects of water extract of mangosteen pericarp (WMP) has been reported, suggesting a potential for the combination of WMP and donepezil (DNP) for AD treatment. Thus, it was evaluated how WMP affects the PK change of donepezil, including systemic exposure and tissue distribution in mice after simultaneous oral administration of DNP with WMP. Firstly, co-treatment of WMP and donepezil showed a stronger inhibitory effect (by 23.0%) on the neurotoxicity induced by Aß(25-35) in SH-SY5Y neuroblastoma cells than donepezil alone, suggesting that the combination of WMP and donepezil may be more effective in moderating neurotoxicity than donepezil alone. In PK interaction, WMP increased donepezil concentration in the brain at 4 h (by 63.6%) after administration without affecting systemic exposure of donepezil. Taken together, our results suggest that WMP might be used in combination with DNP as a therapy for AD.

Simultaneous bioanalysis and pharmacokinetic interaction study of acebrophylline, levocetirizine and pranlukast in Sprague-Dawley rats.

The combination of acebrophylline (ABP), levocetirizine (LCZ) and pranlukast (PRN) is used to treat allergic rhinitis, asthma, hay-fever and other conditions where patients experience difficulty in breathing. This study was carried out with the aim of developing and validating a reverse-phase high-performance liquid chromatographic bioanalytical method to simultaneously quantitate ABP, LCZ and PRN in rat plasma. The objective also includes determination of the pharmacokinetic interaction of these three drugs after administration via the oral route after individual and combination treatment in rat. Optimum resolution between the analytes was observed with a C18 Kinetex column (250 mm × 4.6 mm × 5 µm). The chromatography was performed in a gradient elution mode with a 1 mL/min flow rate. The calibration curves were linear over the concentration range of 100-1600 ng/mL. The intra- and inter-day precision and accuracy were found to be within acceptable limits as specified in US Food and Drug Administration guideline for bioanalytical method validation. The analytes were stable on the bench-top (8 h), after three freeze-thaw cycles, in the autosampler (8 h) and as a dry extract (-80°C for 48 h). The statistical results of the pharmacokinetic study in Sprague-Dawley rats showed a significant change in pharmacokinetic parameters for PRN upon co-administration of the three drugs.

Investigation of pharmacokinetic interaction between ivermectin and praziquantel after oral administration in healthy dogs.

The purpose of this study was to determine the pharmacokinetic interaction between ivermectin (0.4 mg/kg) and praziquantel (10 mg/kg) administered either alone or co-administered to dogs after oral treatment. Twelve healthy cross-bred dogs (weighing 18-21 kg, aged 1-3 years) were allocated randomly into two groups of six dogs (four females, two males) each. In first group, the tablet forms of praziquantel and ivermectin were administered using a crossover design with a 15-day washout period, respectively. Second group received tablet form of ivermectin plus praziquantel. The plasma concentrations of ivermectin and praziquantel were determined by high-performance liquid chromatography using a fluorescence and ultraviolet detector, respectively. The pharmacokinetic parameters of ivermectin following oral alone-administration were as follows: elimination half-life (t1/2λz ) 110 ± 11.06 hr, area under the plasma concentration-time curve (AUC0-∞ ) 7,805 ± 1,768 hr. ng/ml, maximum concentration (Cmax ) 137 ± 48.09 ng/ml, and time to reach Cmax (Tmax ) 14.0 ± 4.90 hr. The pharmacokinetic parameters of praziquantel following oral alone-administration were as follows: t1/2λz 7.39 ± 3.86 hr, AUC0-∞ 4,301 ± 1,253 hr. ng/ml, Cmax 897 ± 245 ng/ml, and Tmax 5.33 ± 0.82 hr. The pharmacokinetics of ivermectin and praziquantel were not changed, except Tmax of praziquantel in the combined group. In conclusion, the combined formulation of ivermectin and praziquantel can be preferred in the treatment and prevention of diseases caused by susceptible parasites in dogs because no pharmacokinetic interaction was determined between them.

Effect of valproic acid on perampanel pharmacokinetics in patients with epilepsy.

We prospectively examined the effect of antiepileptic (AED) cotherapy on steady state plasma concentrations of perampanel (PMP) in epileptic patients. We classified AEDs as strong enzyme inducers (carbamazepine, phenobarbital, phenytoin, oxcarbazepine), not strong enzyme inducers/not inhibitors (levetiracetam, lamotrigine, topiramate, rufinamide, lacosamide, zonisamide, clobazam), and enzyme inhibitors (valproic acid [VPA]). The main outcome was the comparison of PMP plasma concentration to weight-adjusted dose ratio (C/D; [µg/mL]/mg kg-1  d-1 ) among comedication subgroups. From 79 patients (42 females, 37 males) aged (mean ± standard deviation) 33 ± 13 years (range = 12-66 years), 114 plasma samples were collected. Twenty-eight patients (44 samples) were cotreated with enzyme inducers (group A), 21 (27 samples) with not strong enzyme inducers/not inhibitors (group B), 21 (31 samples) with not strong enzyme inducers/not inhibitors + VPA (group C), and 9 (12 samples) with enzyme inducers + VPA (group D). PMP C/D was reduced (-56%, P < .001) in group A (1.79 ± 0.80) versus group B (4.05 ± 2.16) and increased (P < .001) in group C (6.72 ± 4.04) compared with groups A (+275%), B (+66%), and D (2.76 ± 2.00, +143%). Our study documents the unpublished higher PMP C/D in patients cotreated with VPA. These findings have both theoretical relevance, suggesting better characterization of PMP metabolic pathways with ad hoc studies, and clinical usefulness in managing patients on AED polytherapy.

Rivaroxaban and macitentan can be coadministered without dose adjustment but the combination of rivaroxaban and St John's wort should be avoided.

AIMS: We assessed the potential mutual interaction of oral macitentan (cytochrome P450 (CYP) 3A4 substrate) at steady-state with single-dose oral rivaroxaban (CYP3A4 and P-glycoprotein substrate) and evaluated the effect of the CYP3A and P-glycoprotein inducer St John's wort (SJW) on the pharmacokinetics of these drugs in healthy volunteers. METHODS: Twelve healthy volunteers completed this open-label, monocentre, two-period, one-sequence phase I clinical trial. The pharmacokinetics of macitentan (10 mg) was assessed on study days 3 (single dose), 15 (steady-state), 16 (impact of rivaroxaban) and 29 (after induction by oral SJW), and of rivaroxaban on days 2 (single dose), 16 (impact of macitentan at steady-state) and 29 (after induction by SJW). Concurrently, we quantified changes of CYP3A activity using oral microdoses of midazolam (30 µg). RESULTS: Rivaroxaban and macitentan did not significantly change the pharmacokinetics of each other. After induction with SJW, CYP3A activity increased by 272% and geometric mean ratios of macitentan AUC decreased by 48% and of Cmax by 45%. Concurrently, also geometric mean ratios of rivaroxaban AUC and Cmax decreased by 25%. CONCLUSIONS: There is no evidence for a relevant pharmacokinetic interaction between macitentan and rivaroxaban suggesting that these two drugs can be combined without dose adjustment. SJW strongly increased CYP3A activity and substantially reduced rivaroxaban and macitentan exposure while estimated net endothelin antagonism only decreased by 20%, which is considered clinically irrelevant. The combination of SJW with rivaroxaban should be avoided.

Pharmacokinetic interaction of aconitine, liquiritin and 6-gingerol in a traditional Chinese herbal formula, Sini Decoction.

1. This study aimed to investigate the pharmacokinetic interaction of the three ingredients in a traditional Chinese herbal formulation, Sini Decoction, and provide evidence for its compatibility mechanism. 2. First, the effect of liquiritin and 6-gingerol on the pharmacokinetic parameters of aconitine was investigated in rats by using a sensitive and reliable LC-MS/MS method. Then the Caco-2 cell monolayer model and Rhodamine-123 uptake assay were used to investigate the effect of liquiritin and 6-gingerol on the absorption of aconitine and the activity of P-gp. 3. The Cmax of aconitine increased significantly (p < 0.05) from 10.34 ± 1.99 to 17.68 ± 2.65 ng/mL with the pretreatment of liquiritin (20 mg/kg), and to 17.43 ± 0.96 ng/mL with 6-gingerol (20 mg/kg). When aconitine was co-administered with liquiritin and 6-gingerol, the Cmax and AUC(0-t) of aconitine increased approximately twofold, and while t1/2 only increased 1.2-fold. The Caco-2 cell monolayer model and Rhodamine-123 uptake assay indicated that both liquiritin and 6-gingerol could increase the absorption of aconitine by inhibiting the activity of P-gp. 4. These results indicated that both liquiritin and 6-gingerol could promote the absorption of aconitine and increase its drug concentration in blood by inhibiting the activity of P-gp, and it could also provide evidence for compatibility mechanism of the traditional Chinese herbal formula, Sini Decoction.

Pharmaco-parasitological evaluation of the ricobendazole plus levamisole nematodicidal combination in cattle.

The goals of the current study were to evaluate the potential pharmacokinetic (PK) interactions and the clinical efficacy occurring after the subcutaneous (s.c.) administration of ricobendazole (RBZ) and levamisole (LEV) given both separately and co-administered to calves naturally infected with susceptible gastrointestinal nematodes. The clinical efficacy was shown in two seasons, winter and spring, with predominance of different nematode populations. Groups of 15 calves were treated with RBZ alone, LEV alone and RBZ + LEV combination, and an untreated group was kept as a Control. RBZ and LEV plasma concentrations were quantified by HPLC. The clinical efficacy was determined by the faecal egg count reduction test. RBZ and LEV have similar plasma persistence, being detected in plasma over 24 hr post-treatment. No PK interactions were observed after the combined treatment, with similar PK parameters (p > .05) obtained for the single-drug and the combination-based strategy. In winter, the observed clinical efficacies were 96%, 99% and 100% for groups treated with RBZ, LEV and RBZ + LEV, respectively; however, in spring, the efficacies were 95%, 93% and 96% for the same groups. Remarkably, the combination was the only treatment that achieved 100% clinical efficacy against both Haemonchus spp and Ostertagia spp in winter; but the increased presence of Ostertagia spp. in spring (28% in untreated group) determined a tendency to reduced efficacies compared to winter time (only 10% of Ostertagia spp. in untreated group), even for the combined treatment. Overall, in a scenario where the nematode population is susceptible, the RBZ + LEV treatment may be a valid combination in cattle to delay the development of resistance, especially in winter when this combination achieved 100% of efficacy. Thus, selection of anthelmintic resistance will never occur. In fact, this is one of the greatest challenges for the whole cattle production system: to be one step ahead of anthelmintic resistance.

A Compositive Strategy to Study the Pharmacokinetics of TCMs: Taking Coptidis Rhizoma, and Coptidis Rhizoma-Glycyrrhizae Radix et Rhizoma as Examples.

Pharmacokinetic studies are crucial for elucidating the effective constituents and formula compatibility of traditional Chinese medicines (TCMs). However, studies have usually been limited to single dosages and detection of systemic blood concentrations. To obtain comprehensive pharmacokinetic information, here we propose a multi-dosage and multi-sampling (blood from portal vein or systemic circulation, and liver) strategy to comparatively study the pharmacokinetics of multi-form TCMs, i.e., pure constituents, TCMs, or TCM formula extracts. Based on this strategy, we studied the pharmacokinetics of pure berberine, berberine in CoptidisRhizoma (CRE), and berberine in CoptidisRhizoma-GlycyrrhizaeRadix etRhizoma extracts (CR-GRE). After simple calculation and comparison of the obtained area under the curve (AUC) values, the results revealed the drastically different pharmacokinetic properties of pure berberine compared to CRE and CR-GRE. The results contribute to explaining the pharmacological loss of berberine activity after purification and the compatibility of the CR-GR drug pair. The results also innovatively showed that it was intestinal absorption that differentiated the pharmacokinetics of CRE and pure berberine, and CRE and CR-GRE. In conclusion, we propose a composite strategy to comparatively study the pharmacokinetics of TCMs, which could provide sufficient information to obtain a comprehensive view, before follow-up mechanism-of-action studies.

Simultaneous determination of epalrestat and puerarin in rat plasma by UHPLC-MS/MS: Application to their pharmacokinetic interaction study.

In the present study, a simple, rapid and reliable ultrahigh-performance liquid chromatography-tandem mass spectrometric (UHPLC-MS/MS) method was developed and validated to determine simultaneously epalrestat (EPA) and puerarin (PUE) in rat plasma for evaluation of the pharmacokinetic interaction of these two drugs. Both the analytes and glipizide (internal standard, IS) were extracted using a protein precipitation method. The separation was performed on a C18 reversed phase column using acetonitrile and 5 mmol/L ammonium acetate in water as the mobile phase with a gradient elution program. The analytes, including IS, were quantified with multiple reaction monitoring under negative ionization mode. The optimized mass transition ion pairs (m/z) were 318.1 → 274.0 for EPA, 415.1 → 266.9 for PUE and 444.2 → 166.9 for IS. The linear calibration curves for EPA and PUE were obtained in the concentration ranges of 10-4167 and 20-8333 ng/mL, respectively (r > 0.99). The current method was successfully applied for the pharmacokinetic interaction study in rats following administration of EPA and PUE alone or co-administration (EPA 15 mg/kg, oral; PUE 30 mg/kg, intravenous). The results showed that the combination of EPA and PUE could increase t1/2 of EPA and reduce Tmax of EPA. These changes indicated that EPA and PUE might cause drug-drug interactions when co-administrated.

Pharmacokinetic herb-drug interactions with traditional Chinese medicine: progress, causes of conflicting results and suggestions for future research.

Traditional Chinese medicine (TCM) has a long history of medical use in China and is still used worldwide. Unexpected herb-drug interactions (HDIs) may lead to adverse drug reactions or loss of therapeutic efficacy of the victim drug. Here, based on searches of Medline, EBSCO, Science Direct and Web of Science using various keywords, we summarize the TCM-derived pharmacokinetic HDIs that were reported from 1990 to 2015 and discuss the underlying mechanisms. In general, many pre-clinical and clinical pharmacokinetic HDIs have been reported. Our searches show that TCMs cause pharmacokinetic interactions with therapeutic drugs mainly by inhibiting or inducing drug-metabolizing enzymes and transporters. However, most of the interactions result from a small number of prescription medications and the actual potential for harm is low. Moreover, such HDIs can be avoided by discontinuing the TCMs. Despite the extensive number of reports on TCM-derived HDIs, the findings are frequently conflicting and can be confusing. The causes of the conflicts vary, but we classified them into three basic categories as follows: (1) complicated nature and poor quality control of TCMs, (2) different responses of various test systems to TCM exposure and (3) diverse study designs. Accordingly, we propose rational study designs for future HDI research. We also propose that a specific authoritative guide be established that provides recommendations for HDI studies. This review provides insights into the progress and challenges in TCM-derived pharmacokinetic HDI research.

Influence of everolimus on the pharmacokinetics of tacrolimus in Japanese renal transplant patients.

OBJECTIVES: To examine whether a trough concentration of everolimus in the therapeutic range of 3-5 ng/mL affects the pharmacokinetics of tacrolimus in renal transplant patients. METHODS: A total of 52 Japanese renal transplant patients receiving tacrolimus were enrolled in this study. In 28 of them, everolimus was co-administered on day 14 after surgery. Changes in the dose-adjusted blood trough concentration of tacrolimus from day 14 to 28 after surgery were investigated. RESULTS: The dose-adjusted blood trough concentration of tacrolimus on day 28 was affected by CYP3A5*3/*3 and hemoglobin level (P < 0.001 and P = 0.007), but not by everolimus (P = 0.171). In addition, there was no change in the dose-adjusted blood trough concentration of tacrolimus in patients before or after everolimus coadministration (P = 0.165). On day 28, there was no correlation between the rate of change in the dose-adjusted blood trough concentration of tacrolimus and the blood trough concentration or area under the plasma concentration-time curve from 0 to 12 h for everolimus after initiation of combination therapy (r = 0.341, P = 0.076 and r = 0.234, P = 0.231). CONCLUSIONS: A pharmacokinetic interaction between tacrolimus and everolimus was not observed clinically in renal transplant patients. Safe and reliable immunosuppressive therapy in renal transplant patients might be achieved using a combination of tacrolimus and everolimus.

In vitro and in vivo identification of metabolites of magnoflorine by LC LTQ-Orbitrap MS and its potential pharmacokinetic interaction in Coptidis Rhizoma decoction in rat.

Magnoflorine, an important aporphine alkaloid in Coptidis Rhizoma, is increasingly attracting research attention because of its pharmacological activities. The in vivo and in vitro metabolism of magnoflorine was investigated by LC LTQ-Orbitrap MS. In vivo samples including rat urine, feces, plasma and bile were collected separately after both oral (50 mg kg(-1) ) and intravenous administration (10 mg kg(-1) ) of magnoflorine, along with in vitro samples prepared by incubating magnoflorine with rat intestinal flora and liver microsome. As a result, 12 metabolites were found in biological samples. Phase I metabolites were identified in all biological samples, while phase II metabolites were mainly detected in urine, plasma and bile. In a pharmacokinetic study, rats were not only dosed with magnoflorine via oral (15, 30 and 60 mg kg(-1) ) and intravenous administration (10 mg kg(-1) ) but also dosed with Coptidis Rhizoma decoction (equivalent to 30 mg kg(-1) of magnoflorine) by intragastric administration to investigate the interaction of magnoflorine with the rest of compounds in Coptidis Rhizoma. Studies showed that magnoflorine possessed lower bioavailability and faster absorption and elimination. However, pharmacokinetic parameters altered significantly (p < 0.05) when magnoflorine was administered in Coptidis Rhizoma decoction. Oral gavage of Coptidis Rhizoma decoction decreased the absorption and elimination rates of magnoflorine, which revealed that there existed pharmacokinetic interactions between magnoflorine and the rest of ingredients in Coptidis Rhizoma.