Human urotensin II in internal mammary and radial arteries of patients undergoing coronary surgery

AimsInternal mammary (IMA) and radial artery (RA) have different incidence of vasospasm and long-term patency rates in arterial grafting. We compared the vasoreactivity of human urotensin II (hU-II) and its receptor with mechanism investigations in IMA and RA.MethodsIMA and RA taken from patients undergoing coronary bypass surgery were studied in organ baths. Urotensin receptor expression was determined by RT-PCR.ResultshU-II contracted IMA with pD₂ of 8.57 ± 0.41 and 45.4 ± 9.1% E_max of contraction to 100 mM KCl, whereas caused less contractile responses in RA (pD₂:8.30 ± 0.79, E_max:20.4 ± 4.8%, p < 0.05). Nifedipine inhibited hU-II-contraction in IMA. In U₄₆₆₁₉-precontraction, hU-II elicited comparable relaxation in IMA (pD₂:8.39 ± 0.43, E_max:56.1 ± 4.0%) and RA (pD₂:9.03 ± 0.46, E_max:65.2 ± 7.1%). The relaxation was abolished by endothelium denudation and by indomethacin, oxadiazoloquinoxalinone or N^ω-nitro-l-arginine, oxyhemoglobin, and Ca²⁺-activated K⁺ channel (K_Ca) blockers. Urotensin receptor mRNA was detected in both arteries.ConclusionshU-II is an important spasmogen in arterial grafts with receptors expressed in IMA and RA. hU-II elicits stronger contraction in IMA than in RA and a moderate endothelium-dependent relaxation attributable to nitric oxide, prostacyclin, and endothelium-derived hyperpolarizing factor with involvement of K_Ca activation. The relaxant response of endothelium-intact IMA and RA to hU-II demonstrates the importance of preservation of endothelium in these grafts.     

Pharmacokinetics and pharmacodynamics of propofol and fentanyl in patients undergoing abdominal aortic surgery – a study of pharmacodynamic drug–drug interactions

Propofol is routinely combined with opioid analgesics to ensure adequate anesthesia during surgery. The aim of the study was to assess the effect of fentanyl on the hypnotic effect of propofol and the possible clinical implications of this interaction. The pharmacokinetic/pharmacodynamic (PK/PD) data were obtained from 11 patients undergoing abdominal aortic surgery, classified as ASA III. Propofol was administered by a target‐controlled infusion system. Fentanyl 2–3 µg/kg was given whenever insufficient analgesia occurred. The bispectral index (BIS) was used to monitor the depth of anesthesia. A population PK/PD analysis with a non‐linear mixed‐effect model (NONMEM 7.2 software) was conducted. Two‐compartment models satisfactorily described the PK of propofol and fentanyl. The delay of the anesthetic effect in relation to PK was described by the effect compartment. The BIS was linked to propofol and fentanyl effect‐site concentrations through an additive E_max model. Context‐sensitive decrement times (CSDT) determined from the final model were used to assess the influence of fentanyl on the recovery after anesthesia. The population PK/PD model was successfully developed to describe simultaneously the time course and variability of propofol and fentanyl concentrations and BIS. Additive propofol–fentanyl interactions were observed and quantitated. The duration of the fentanyl infusion had minimal effect on CSDT when it was shorter than the duration of the propofol infusion. If the fentanyl infusion was longer than the propofol infusion, an almost two‐fold increase in CSDT occurred. Additional doses of fentanyl administered after the cessation of the propofol infusion result in lower BIS values, and can prolong the time of recovery from anesthesia. Copyright © 2016 John Wiley & Sons, Ltd.     

The pharmacokinetics and hypoglycaemic effect of sunitinib in the diabetic rabbits

BackgroundDiabetes is one of the most common metabolic diseases in the world, which may influence changes in the pharmacokinetics and pharmacodynamics of drugs. Sunitinib is a tyrosine kinase inhibitor (TKI) broadly used for treatment of numerous cancers, which exhibits the side hypoglycaemic effect. The aim of the study was a comparison of concentrations and pharmacokinetics of sunitinib after a single administration in rabbits with hyperglycaemia and normoglycaemia (control group). Additionally, the effect of sunitinib on glucose levels was investigated.MethodsThe research was carried out on a control group (n = 6) and a group of rabbits with diabetes (n = 6). The rabbits were treated with sunitinib in the oral dose of 25 mg. Plasma concentrations of sunitinib and its metabolite (SU12662) were measured with validated HPLC method with UV detection.ResultsThe comparison of the sunitinib C_max and AUC_0–∞ in the diabetic group with the control group gave the ratios of 1.63 [90% confidence interval (CI) [1.59; 1.66] and 2.03 [1.97; 2.09], respectively. Statistically significant differences between the analyzed groups were revealed for C_max (p = 0.006), AUC_0–∞ (p = 0.0088), and AUC_kel (p = 0.009). The maximum glycaemia drop of 14.4–69.6% and 15.4–33.5% was observed in the diabetic animals and in the control group, respectively. The glycaemia values returned to the initial values in 24 h after the administration of the drug.ConclusionsThe research proved the significant influence of diabetes on the pharmacokinetics of sunitinib and it confirmed the hypoglycaemic effect of the TKI in diabetic rabbits and in normoglycaemia.     

Influence of sex and CYP2D6 genotype on mirtazapine disposition, evaluated in Spanish healthy volunteers

AimsTo evaluate the influence of sex and CYP2D6 genotype on mirtazapine disposition within two bioequivalence studies in healthy volunteers.MethodsSeventy-two healthy volunteers were included in two standard 2 × 2 crossover bioequivalence trials. Subjects received a single 30-mg oral dose of each mirtazapine formulation in each study period. Plasma concentrations were measured from 0 to 96 or 120 h by a HPLC with coupled mass spectrometry validated method. CYP2D6 genotyping was available for 68 subjects that were classified into three phenotypic groups depending on the number of active gene copies: extensive/ultrarapid metabolizers (UM-EM), intermediate (IM) and poor metabolizers (PM). To evaluate the influence of sex and genotype on mirtazapine disposition we performed a linear mixed model for repeated measures. Pharmacokinetic data were log-transformed and AUC and C_max adjusted to the administered dose/weight. Factors included in the model were centre, formulation, period, sequence, sex and genotype as fixed effects, and subject nested sequence × sex × genotype as random one. A second model was also performed adding the interaction sex × genotype to the previous model.ResultsMirtazapine disposition evaluated as AUC_0–∞ is influenced by sex (p = 0.007) and CYP2D6 phenotype group (p = 0.01). Attending to the theoretical figures provided by the model, mean (95% CI) dose/weight adjusted AUC_0–∞ (ng h/ml)/(mg/kg) is 1516.62 (1411.27–1628.22) in EM/UM, 1613.63 (1482.14–1758.55) in IM and 2049.28 (1779.78–2357.24) in PM. In the case of C_max these figures also show a trend to higher values in PM, but it did not reach statistical significance. Females show a lower dose/weight adjusted AUC_0–∞: 1594.39 (1477.70–1720.28) vs. 1837.65 (1694.67–1992.70). On the contrary dose/weight adjusted C_max is higher in females than in males: 38.33 (34.79–42.28) vs. 32.66 (29.44–36.21).ConclusionsBoth CYP2D6 genotype group and sex influence the disposition of mirtazapine in healthy volunteers and confirm reported data in the literature obtained by different methods. No sex-by-genotype interaction could be detected.     

Evaluation of bioimpedance spectroscopy for the measurement of body fluid compartment volumes in rats

IntroductionBioimpedance spectroscopy (BIS) has been used in human and large animal research to assess body fluid compartment volumes (BFC) such as total body water (TBW), extracellular fluid volume (ECFV), and intracellular fluid volume (ICFV). To date, the application of BIS for determination of BFC in small research animals has been limited.MethodsWe sought to evaluate the sensitivity and consistency of BIS for the determination of BFC in male SD rats. Thus, in separate series of experiments, we a) compared BFC values determined using BIS to BFC values obtained using radioisotope indicator dilution methods; b) examined day-to-day intra- and inter-rat BFC variability in small (267.8 ± 5.4 g) and large (372.6 ± 5.6 g) rats (n = 8/group) as compared to empirical normative mammalian values; c) evaluated the sensitivity of BIS to detect time-dependent responses to repeated administration of a potent diuretic; and d) compared empirically generated BFC data to predicted osmotically-induced ECFV and ICFV shifts in response to i.v. administration of hypotonic (0.3%), isotonic (0.9%) or hypertonic (3.0%) saline (n = 6/concentration).ResultsBFC values generated using radioisotope dilution agreed with those generated using BIS. BIS reliably detected differences between small and large rats (p < 0.001), and was associated with low (< 3.5%) day-to-day, intra-animal coefficient of variation (% = Standard Deviation/mean). BIS detected small reductions (~ 10%) in ECFV induced by as few as 2 days of the loop diuretic, furosemide, relative to vehicle treatment (70.8 ± 1.5 ml vs. 84.0 ± 1.5 ml; respectively, p < 0.05). BIS rapidly detected shifts between ECFV and ICFV in response to osmotic saline challenge, and these responses were similar to physiologically predicted responses.DiscussionThe current studies support using BIS as a means of sensitively and reliably performing repeated measurements of BFC in rats of a) differing sizes, b) in response to therapeutic agents known to influence renal sodium handling and c) in response to osmotic challenge.     

Inhibition of T-cell activation and proliferation by mycophenolic acid in patients awaiting liver transplantation: PK/PD relationships

Mycophenolic acid (MPA) plasma concentrations were reported to be associated with a decrease in T-cell proliferation, and in both IL-2 α-chain (CD25) and transferin receptor (CD71) expression. The aim of this study was to confirm, quantify and model these PK/PD relationships.Full profiles of MPA plasma concentrations, T-cell proliferation, intracytoplasmic IL-2 and TNF-α expression, and both CD71 and CD25 expression were collected over the 12 h after dosing in 10 patients on the waiting list for liver transplantation. Data were analyzed using NONMEM^®.Both CD25 and CD71 expression and T cell proliferation clearly decreased (median of decrease from baseline 62%, 68% and 94%, respectively) with increasing MPA concentrations, in contrast to IL-2 and TNF-α expression. The CD25 and CD71 baseline expression (E₀) and maximum effect (E_max) were correlated with the E₀ and E_max values of T-cell proliferation (r² = 0.509 and r² = 0.622, respectively). The CD25, CD71 expression and T-cell proliferation profiles were adequately fitted using a sigmoid inhibitory E_max model. Low estimated values (≤2 mg/L) for 50% inhibitory MPA concentrations were obtained. This study confirmed a transient MPA concentration-dependent decrease in T-cells expressing CD25 and CD71 and a strong reduction of T-cell proliferation and showed that CD25 and CD71 expression was correlated with T-cell proliferation.     

Pharmacokinetics of oxycodone hydrochloride and three of its metabolites after intravenous administration in Chinese patients with pain

ObjectivesThe aim of this study is to evaluate the pharmacokinetic profile of oxycodone and three of its metabolites, noroxycodone, oxymorphone and noroxymorphone after intravenous administration in Chinese patients with pain.MethodsForty-two subjects were assigned to receive intravenous administration of oxycodone hydrochloride of 2.5, 5 or 10 mg. Plasma and urine samples were collected for up to 24 h after intravenous administration of oxycodone hydrochloride.ResultsPharmacokinetic parameters showed that mean values of C_max, AUC_0–t and AUC_0–∞ of oxycodone were dose dependent, whereas T_max and t_1/2 were not. The mean AUC_0–t ratio of noroxycodone to oxycodone ranged from 0.35 to 0.42 over three doses, and those of noroxymorphone, or oxymorphone, to oxycodone were ranging of 0.06–0.08 and 0.007–0.008, respectively. Oxycodone and its three metabolites were excreted from urine. Approximately 10% of unchanged oxycodone was recovered in 24 h. Most adverse events (AEs) reported were mild to moderate. The frequently occurred AEs were dizziness, nausea, vomiting, drowsiness and fatigue. No dose-related AEs were found.ConclusionOur pharmacokinetics of oxycodone injection in Chinese patients with pain strongly support continued development of oxycodone as an effective analgesic drug in China.     

In vivo and in vitro evaluation of the estrogenic properties of the 17β-(butylamino)-1,3,5(10)-estratrien-3-ol (buame) related to 17β-estradiol

BackgroundBuame [17β-(butylamino)-1,3,5(10)-estratrien-3-ol] possesses anticoagulant and antiplatelet activities that are potentially antithrombotic. Since its estrogenicity is unknown, it was evaluated by established methods.MethodsBuame (10, 100, 500, and 1,000 μg/kg), 17β-estradiol (E₂) (100 μg/kg), or propylene glycol (10 ml/kg) were subcutaneously (sc) administered for three days to immature Wistar female rats (21 days old). The relative uterotrophic effect to E₂ was 78 (E₂ = 100) with a relative uterotrophic potency of 1.48 (E₂ = 100). Adult ovariectomized Wistar rats received an sc injection at 8:00 h (reversed cycle) of: 7.5 μg of E₂ (≈ 30 μg/kg), buame (≈ 750, 1,500, 3,000 μg/kg), or corn oil (≈ 1.2 ml/kg). After 24 h, progesterone (4–5 mg/kg) was administered. Sexual receptivity was assessed 5 to 7 h later, and the lordosis quotient (LQ; number lordosis/number mounts × 100) was evaluated.ResultsBuame induced lordosis (LQmax 85 ± 9; ED50 952 ± 19 μg/kg) and E₂ LQmax 56 ± 8; ED50 10 ± 2 μg/kg; the relative LQpotency was 0.51 (E₂ = 100). Buame competed with [³H]E₂ for the estrogen receptor (Buame RBA = 0.15 and Ki = 5.9 × 10^?7 M; E₂ RBA = 100; Ki = 6.6 × 10^?9 M). Buame increased MCF-7 cells proliferation, from 10^?11 to 10^?9 M, its proliferative effect was 1.73–1.79 (E₂ = 3.0–3.9); its relative proliferative effect to E₂ was 33–40% (E₂ = 100%) and relative potency 10.4–10.7 (E₂ = 100). Tamoxifen and fulvestrant (ICI 182,780) inhibited buame's proliferation indicating mediation through estrogen receptors in this response.ConclusionBuame is therefore an estrogen partial agonist with a weak estrogenic activity.     

Effect of total and partial nephrectomy on the elimination of ciprofloxacin in humans

BackgroundRenal cell carcinoma (RCC) is the most common form of kidney cancer. Surgery is a standard procedure to resect the tumor during total (TN) or partial (nephron-sparing) nephrectomy (PN). Ciprofloxacin is most often administered at the usual intravenous dose of 100–400 mg/12 h. The application of such low doses of ciprofloxacin as 200 mg/24 h carries the risk of achieving subtherapeutic concentrations even in patients with limited renal function. The aim of the study was a comparison of concentrations and pharmacokinetics for ciprofloxacin at steady-state in patients after total and partial nephrectomy and evaluation of the effectiveness of the iv dose 200 mg/24 h against the theoretical value of MIC, 0.5 μg/ml.MethodsThe research was carried out on two groups of patients after nephrectomy: total (group 1, n = 21; mean [SD], age, 62.9 [14.4] years; weight, 76.0 [14.6] kg; creatinine clearance, clcr, 90.7 [22.2] ml/min) and partial (group 2, n = 15; 61.7 [9.3] years; 87.8 [16.4] kg; CL_CR, 107.8 [36.4] ml/min). The patients were treated with ciprofloxacin in the dose of 200 mg/24 h (iv). Plasma concentrations of ciprofloxacin at steady state were measured with validated HPLC method with UV detection.ResultsThe mean values of plasma concentrations of ciprofloxacin at steady state in group 1 and 2 were: C^ss_max, 2.012 and 1.345; C^ss_min, 0.437 and 0.244 μg/ml, respectively. The main pharmacokinetic parameters for ciprofloxacin in group 1 and 2 were as follows: AUC_(0–last), 30.9 [17.9] and 19.5 [8.7] μg h/ml; AUMC_(0–last), 177.91 [11.1] and 91.9 [66.5] μg h²/ ml; _t1/2β, 13.9 [7.7] and 9.8 [3.3] h; MRT, 16.5 [12.1] and 9.77 [5.4] h; V_d, 115.0 [67.2] and 142.2 [78.7] l; CL, 6.2 [3.3] and 10.8 [5.7] l/h, respectively. With the assumed MIC = 0.5 μg/ml, the values of C^ss_max/MIC < 10 and AUC/MIC < 125 were obtained in all the patients.ConclusionIn our patients we observed significant differences in some pharmacokinetic parameters of ciprofloxacin after two types of nephrectomy.     

Preparation of estradiol chitosan nanoparticles for improving nasal absorption and brain targeting

The estradiol(E₂)-loaded chitosan nanoparticles (CS-NPs) were prepared by ionic gelation of chitosan with tripolyphosphate anions (TPP). The CS-NPs had a mean size of (269.3 ± 31.6) nm, a zeta potential of +25.4 mV, and loading capacity of E₂ CS-NPs suspension was 1.9 mg ml⁻¹, entrapment efficiency was 64.7% on average. Subsequently, this paper investigated the levels of E₂ in blood and the cerebrospinal fluid (CSF) in rats following intranasal administration of E₂ CS-NPs. E₂-loaded CS-NPs were administered to male Wister rats either intranasally or intravenously at the dose of 0.48 mg kg⁻¹. The plasma levels achieved following intranasal administration (32.7 ± 10.1 ng ml⁻¹; t_max 28 ± 4.5 min) were significantly lower than those after intravenous administration (151.4 ± 28.2 ng ml⁻¹), while CSF concentrations achieved after intranasal administration (76.4 ± 14.0 ng ml⁻¹; t_max 28 ± 17.9 min) were significantly higher than those after intravenous administration (29.5 ± 7.4 ng ml⁻¹ t_max 60 min). The drug targeting index (DTI) of nasal route was 3.2, percent of drug targeting (DTP%) was 68.4%. These results showed that the E₂ must be directly transported from the nasal cavity into the CSF in rats. Finally, compared with E₂ inclusion complex, CS-NPs improved significantly E₂ being transported into central nervous system (CNS).     

Pharmacokinetics of garenoxacin in elderly patients with respiratory tract infections

The pharmacokinetics of the new oral des-fluoroquinolone antimicrobial garenoxacin (GRNX) was investigated in elderly patients with respiratory tract infections. Patients were treated with GRNX (200 mg or 400 mg) once daily for 7 days. Plasma GRNX concentrations were determined and pharmacokinetic parameters were estimated by Bayesian predictions using reported population pharmacokinetic parameters. At each dose, the maximum plasma concentration (C_max) and the area under the concentration–time curve (AUC) were comparable with those reported in young subjects, except that the estimated C_max and AUC values in one patient receiving the 200 mg dose whose body weight and creatinine clearance rate (CL_Cr) were 38 kg and 17 mL/min, respectively, were higher than those of the other patients given 200 mg GRNX and were comparable with those of patients who received the 400 mg dose. These results suggest that the recommended dose of GRNX should be 400 mg for most elderly and young patients, but only 200 mg in patients whose body weight and CL_Cr are <40 kg and <30 mL/min, respectively.     

Kaempferol-induces vasorelaxation via endothelium-independent pathways in rat isolated pulmonary artery

Background

Kaempferol, a flavonoid, is the essential part of human diet. Flavonoids have different pharmacological activities like cardioprotective, anti-inflammatory and anti-oxidant. The aim of current study was to investigate vasorelaxant potential of kaempferol on rat isolated pulmonary artery and to assess the underling mechanisms.

Co-treatment of mouse antral follicles with 17β-estradiol interferes with mono-2-ethylhexyl phthalate (MEHP)-induced atresia and altered apoptosis gene expression

Mono-2-ethyhexyl phthalate (MEHP) is a metabolite of a plasticizer found in many consumer products. MEHP inhibits mouse ovarian follicle growth by reducing 17β-estradiol (E₂) production. Yet, whether MEHP causes follicle death (atresia) is unclear. We hypothesized that MEHP causes atresia by altering apoptosis gene expression, and that E₂ co-treatment blocks these effects. Follicles were exposed to MEHP (0.36–36 μM) ± E₂ for 48–96 h to determine the effect of MEHP ± E₂ on atresia and gene expression. MEHP increased atresia, but this effect was blocked by co-treatment with E₂. MEHP increased the expression of the pro-apoptotic gene Aifm1, but decreased that of the pro-apoptotic gene Bok and the anti-apoptotic gene Bcl2l10. E₂ interfered with MEHP-induced changes in Aifm1 and Bcl2l10. Our findings suggest that decreased E₂ levels are required for MEHP-induced follicle atresia and that Aifm1, Bok, and Bcl2l10 are involved in this process.     

Changes in ambient temperature differentially alter the thermoregulatory,cardiac and locomotor stimulant effects of 4-methylmethcathinone (mephedrone)

BackgroundThe substituted cathinone compound known as mephedrone (4-methylmethcathinone; 4-MMC) has become popular with recreational users of psychomotor-stimulant compounds. Only recently have the first preclinical studies provided information about this drug in the scientific literature; nevertheless, media reports have led to drug control actions in the UK and across several US states. Rodent studies indicate that 4-MMC exhibits neuropharmacological similarity to 3,4-methylenedioxymethamphetamine (MDMA) and prompt investigation of the thermoregulatory, cardiac and locomotor effects of 4-MMC. This study focuses on the role of ambient temperature, which has been shown to shift the effects of MDMA from hyperthermic to hypothermic.MethodsMale Sprague-Dawley rats were monitored after subcutaneous administration of 4-MMC (1.0–5.6 mg/kg) using an implantable radiotelemetry system under conditions of low (20 °C) and high (30 °C) ambient temperature.ResultsA pharmacokinetic study found a T_max of 0.25 h and a C_max of 1206 ng/ml after 5.6 mg/kg 4-MMC. A dose-dependent reduction of body temperature was produced by 4-MMC at 20 °C but there was no temperature change at 30 °C. Increased locomotor activity was observed after 4-MMC administration under both ambient temperatures, however, significantly more activity was observed at 30 °C. Heart rate was slowed by 1.0 and 5.6 mg/kg 4-MMC at 20 °C, and was slower in the 30 °C vs. 20 °C condition across all treatments.ConclusionThese results show that the cathinone analog 4-MMC exhibits in vivo thermoregulatory properties that are distinct from those produced by MDMA.     

Normothermic and hypothermic models for studying the deleterious effects of hypoxia-reoxygenation on EDHF-mediated relaxation in isolated porcine coronary arteries

IntroductionThe vasomotor response of the coronary artery is altered by hypoxia–reoxygenation (H–R) induced damage. The aim of our study was to compare and evaluate normothermic and hypothermic models which are suitable for future drug studies of vasoprotective action against H–R injury.MethodsPorcine coronary arterial rings were isolated and placed in Krebs–Henseleit (K–H) solution. Rings were exposed to normoxic conditions (control group) and two different H–R conditions: the first induced by a 95% N₂–5% CO₂ gas mixture (40- and 60-min hypoxia) in a normothermic protocol, and the second induced by hypothermic (4 °C) hypoxia–reoxygenation in an air-tight beaker filled with K–H solution (24- and 48-hours hypoxia). Reoxygenation was applied by introducing K–H solution aerated with a 95% O₂–5% CO₂ mixture under normothermic (37 °C) conditions. To test the EDHF-mediated relaxation by substance P, rings were first incubated in L-NNA, nitric oxide synthase inhibitor, and indomethacin, cyclooxygenase inhibitor, and then pre-contracted with thromboxane analogue U-46619. Analysis of the maximum relaxation of the arterial rings was performed by one-way ANOVA, followed by Bonferroni's post-test.ResultsDistal segments of the coronary artery responded faster to contraction induced by U-46619 and were relaxed by substance P to a greater extent than proximal segments. Maximal relaxations of arterial rings induced by a 10 nM solution of substance P were significantly reduced (p < 0.001) from the values for normoxic rings (81.0 ± 1.0%, n = 30) after 40-min H–R (50.5 ± 5.3%, n = 30), 60-min H–R (32.1 ± 3.5%, n = 30), 24-hours hypothermic H–R (56.0 ± 2.3%, n = 30) and after 48-hours hypothermic H–R (38.5 ± 5.1%, n = 30).ConclusionsThe model employing 40-min normothermic H–R is as effective as 24-hours hypothermic H–R, and 60-min normothermic H–R as 48-hours hypothermic H–R for studying the deleterious effects of H–R on EDHF-mediated relaxation.     

Comparison of average,scaled average,and population bioequivalence methods for assessment of highly variable drugs: An experience with doxifluridine in beagle dogs

Several strategies for overcoming the challenge of establishing bioequivalence (BE) for highly variable drugs (HVDs; drugs having within-subject variability >0.3) have been considered in recent years. Within-subject variability of the area under the curve (AUC_4 h) and peak concentration (C_max) of doxifluridine in the minimal group (n = 24) were 0.444 and 0.491, respectively, meeting the criteria for an HVD. For the large group (n = 60), within-subject variability of the AUC_4 h and C_max were 0.431 and 0.493, respectively. The 90% confidence interval for the AUC_4 h and C_max of the ratio of the test drug to the reference drug exceeded the acceptable BE limits (0.80–1.25) of the ABE (average bioequivalence), in both the minimal and large groups. However, the 90% CI fell within the extended BE limits (0.61–1.64) of the SABE (scaled average bioequivalence), calculated using within-subject variability. The 95% CI of the AUC_4 h and C_max of the ratio of test to reference drug were within the extended BE limit (<1.73) of the PBE (population bioequivalence), calculated using total variance. Our results suggest that the SABE method may be useful for evaluating the BE of HVDs and for meeting the need for international guidelines for BE.     

Nisoxetine blocks sodium currents and elicits spinal anesthesia in rats

BackgroundAlthough nisoxetine has been shown to elicit infiltrative cutaneous local anesthesia, the inhibition of voltage-gated Na⁺ channels by nisoxetine has not been reported. The aim of this study was to evaluate the effect of nisoxetine on Na⁺ currents and its efficacy on spinal anesthesia.MethodsIn in vitro studies, the voltage-clamp method was employed to examine whether nisoxetine blocked Na⁺ currents in mouse neuroblastoma N2A cells.ResultsMepivacaine showed concentration- and state-dependent effect on tonic blockade of voltage-gated Na⁺ currents (IC50 of 3.7 and 74.2 μM at holding potentials of ?70 and ?100 mV, respectively). Nisoxetine was more potent (IC₅₀ of 1.6 and 28.6 μM at holding potentials of ?70 and ?100 mV, respectively). In in vivo studies, after rats were intrathecally injected with nisoxetine and mepivacaine, the dose-response curves were constructed. Nisoxetine acted like local anesthetic mepivacaine and induced spinal anesthesia with a more sensory-selective action (p < 0.05) over motor blockade in a dose-related fashion. Intrathecal 5% dextrose (vehicle) produced no spinal anesthesia. On the 50% effective dose (ED₅₀) basis, nisoxetine elicited more potent spinal anesthesia than did mepivacaine (p < 0.05).ConclusionsOur results showed that nisoxetine displayed a more potent and prolonged spinal anesthesia with a more sensory/nociceptive-selective action over motor blockade, compared with mepivacaine. The local anesthetic effect of nisoxetine could be probably due to the suppression of Na⁺ currents.     

Characterization and structure-activity relationship of natural flavonoids as hERG K+ channel modulators

ObjectivesFlavonoids are present in varying concentrations in plant foods and have been reported to have numerous pharmacological activities, such as anti-cancer, antioxidant, anti-inflammatory, hepatoprotective, and vasodilator effects. We found that quercetin, fisetin, and some related flavonoid derivatives could inhibit human ether-à-go-go-related gene (hERG) K⁺ channels.Key findingsIn this study, we tested the effects of a series of flavonoids on the hERG K⁺ channel expressed in HEK293 cells. For the first time, we demonstrate that quercetin and fisetin (Fise) are potent hERG current blockers. The 50% inhibiting concentration (IC₅₀) and maximum efficacy (E_max) of quercetin were 11.8 ± 0.9 μM and 82 ± 2%, while those of fisetin were 38.4 ± 6 μM and 100 ± 6%, respectively. Luteolin (Lute) was a less potent inhibitor of hERG current (48 ± 1% at 100 μM). Galangin, kaempferol, and isorhamnetin (100 μM) showed weaker activity on the hERG currents.ConclusionThese results suggest that quercetin, fisetin, and luteolin are potent hERG K⁺ channel inhibitors and reveal the structure-activity relationship of natural flavonoids.     

Alteration of pharmacokinetics of proguanil in healthy volunteers following concurrent administration of efavirenz

Efavirenz and proguanil are likely to be administered concurrently for the treatment of patients with HIV and malaria. The metabolism of proguanil is mediated principally by CYP2C19 while efavirenz is known to inhibit this enzyme. This study therefore investigated the effect of efavirenz on proguanil disposition. Fifteen healthy volunteers were each given 300 mg single oral doses of proguanil alone or with the 9th dose of efavirenz (400 mg daily for 11 days) in a crossover fashion. Blood samples were collected at pre-determined time intervals and analyzed for proguanil and its major metabolite, cycloguanil, using a validated HPLC method. Co-administration of proguanil and efavirenz resulted in significant increases (p < 0.05) in C_max, T_max, AUC_T and elimination half-life (T_1/2β) of proguanil compared with values for proguanil alone [C_max: 2.55 ± 0.24 mg/l vs 3.75 ± 0.48 mg/l; T_max: 2.80 ± 0.99 h vs 4.80 ± 0.99 h; AUC_T: 45.58 ± 12.75 mg h/l vs 97.00 ± 23.33 mg h/l; T_1/2β: 16.50 ± 4.55 h vs 23.24 ± 4.08 h]. Also, efavirenz caused a pronounced decrease in the AUC(metabolite)/AUC(unchanged drug) ratio of proguanil along with a significant decrease (p < 0.05) in C_max and AUC of the metabolite.These results indicate that efavirenz significantly alters the pharmacokinetics of proguanil. These suggest that the protection against malaria by proguanil may be decreased when the drug is co-administered with efavirenz and the antimalarial efficacy is dependent on cycloguanil plasma levels.