Measurement of plasma concentrations of isosorbide dinitrate

Concentrations of the vasodilator isosorbide dinitrate (ISDN) in human plasma can be measured with good sensitivity (about 0·2–0·5 ng ml^?1) using electron-capture gas chromatography after a one-stage extraction. The mean recovery of ISDN from plasma was 83 per cent ± 9 standard deviation (S.D.). The precision of the method for the measurement of ISDN in plasma ranged from ± 14 per cent at 1 ng ml^?1 to ± 7 per cent at 5 ng ml^?1 to ± 4 per cent at 50 ng ml^?1. The 95 per cent confidence limits of the least-squares regression calibration line forced through the origin were ± 100 per cent at 1 ng ml^?1, ± 11 per cent at 10 ng ml^?1, and ± 8 per cent at 30 ng ml^?1. The method has been used to assay many samples withdrawn after doses of drug at therapeutic levels to normal subjects.     

Microcystin-LR and nodularin induce intracellular glutathione alteration, reactive oxygen species production and lipid peroxidation in primary cultured rat hepatocytes

Microcystin-LR (MCYST-LR) and nodularin (NOD) produced by cyanobacteria are potent specific hepatotoxins. However, the mechanisms of their hepatotoxicity have not been fully elucidated. In the present study the effect of non cytotoxic low concentrations of MCYST-LR and NOD on intracellular reduced glutathione (GSH) alteration, reactive oxygen species (ROS) production and lipid peroxidation was investigated in primary cultured rat hepatocytes. Cell viability was determined by the methylthiazoltetrazolium (MTT) dye assay, reduced GSH was evaluated by enzymatic methods, ROS were evaluated by the dichlorofluorescein diacetate (H2DCF-DA) fluorescent probe and lipid peroxidation by dosing malondialdehyde (MDA) by the thiobarbituric acid method. The 24 h LC50 values of MCYST-LR and NOD were 48 and 62 ng/ml, respectively. Exposure of freshly isolated rat hepatocytes to MCYST-LR or NOD at non cytotoxic low concentrations (2, 10 ng/ml) for 3, 24 and 48 h periods resulted in a significant rise of GSH levels and production of ROS. NOD significantly induced in a time- and concentration-dependent lipid peroxidation. However, MCYST-LR treatment did result in a significant decrease in MDA levels compared with controls. Although MCYST-LR and NOD are closely related in terms of structure and inhibition of protein phosphatases, they induce differently the oxidative stress at non cytotoxic low concentrations. Therefore, the results indicate that oxidative stress mediated by reactive intermediates may be a mechanism by which these cyanotoxins induce their hepatotoxic effect.     

Dose-dependent in-vivo toxicity assessment of silver nanoparticle in Wistar rats

This study aims to suggest the limits of silver nanoparticle (AgNP) uses for medicinal purpose and was performed to explore the effect of various doses of silver nanoparticle in rats. Four different doses of AgNP (4, 10, 20, and 40?mg/kg) were injected intravenously. For safety evaluation of injected AgNP, body weight, organ coefficient, whole blood count, and biochemistry panel assay for liver function enzyme (AST, ALT, ALP, and GGTP), comet assay, ROS, and histological parameter were performed; 10–12 week old animals were randomly divided into groups of six individuals each for control, and doses of 40, 20, 10, and 4?mg/kg AgNP injected. Significant changes were observed (p?<?0.01) in hematological parameters (WBC count, platelets counts, haemoglobin, and RBC count) in the 40 and 20?mg/kg groups. The changes were non-significant in the other groups (4 and 10?mg/kg group). In the 40?mg/kg group, a significant increase was also found in liver function enzymes like ALT and AST (p?<?0.01), ALP (p?<?0.01), GGTP (p?<?0.01), and bilirubin (p?<?0.01). ROS in blood serum increased in the high dose group. Tail migration in single cell gel electrophoresis in the 40, 20, 10, 4?mg/kg, and control groups was 34.9, 29.5, 17.8, 5.8, and 0.0 µm, respectively, which indicated damage in the DNA strand in the high dose group. EDXRF showed a ～ 10-times increase in silver concentration in the 40?mg/kg group and TEM image also showed particle deposition in the 40?mg/kg group. This study indicates that the AgNP in doses (< 10?mg/kg) is safe for biomedical application and has no side-effects, but its high dose (> 20?mg/kg) is toxic.     

LC-MS-MS analysis of 2-pyridylacetic acid,a major metabolite of betahistine: application to a pharmacokinetic study in healthy volunteers

1.?A sensitive liquid chromatographic-tandem mass spectrometric assay was developed and validated to determine the major metabolite of betahistine, 2-pyridylacetic acid, in human plasma.

2.?The analyte was extracted from plasma samples by liquid–liquid extraction and analysed using liquid chromatography-tandem mass spectrometry with an electrospray ionization interface. The method has a lower limit of quantitation of 1?ng?ml^?1 for a 0.5-ml plasma aliquot. The intra- and interday precision (relative standard deviation), calculated from quality control (QC) samples, was less than 10%. Accuracy as determined from QC samples was within ±7%.

3.?The validated method was successfully applied to a pharmacokinetic study of betahistine in healthy volunteers. After oral administration of a single dose of 24?mg betahistine mesylate to 20 healthy Chinese male volunteers, C_max was 339.4?ng?ml^?1 (range 77.3–776.4?ng?ml^?1). The t_1/2 was 5.2?h (range 2.0^?1?11.4?h). The AUC_0?t obtained was 1153.5?ng?ml^?1?h (range 278.5–3150.8?ng ml^?1?h). The disposition of the metabolite exhibited a marked interindividual variation.

4.?The plasma concentrations of the parent drug were less than 0.5?ng ml^?1, suggesting that it undergoes almost complete first-pass metabolism. The reported two active metabolites were not detected in the plasma of any volunteer. Although there is no evidence that the major metabolite has pharmacological activity, the clinical importance of 2-pyridylacetic acid in humans should be reinvestigated.     

Comet assay reveals no genotoxicity risk of cationic solid lipid nanoparticles

Cationic solid lipid nanoparticles (cSLN) are colloidal carriers for genes or drugs, particularly lipophilic drugs. Several reports exist on their high efficiency, but only a few studies report the effect of cSLNs on living cells. In the present work, internalization, cell viability (alamar blue assay) and genotoxic potential (alkaline comet assay) of three cSLN formulations (A–C) were evaluated in HepG2 and Caco‐2 cells. cSLN showed an average hydrodynamic diameter (z‐ave) of 141–222 nm, zeta‐potential of 55.0–72.5 mV and polidispersity indices (PdI) of 0.336–0.421. Dispersion in physiological buffers increased z‐ave and PdI. 0.01 mg ml^–1 cSLN unaffected cell viability, but 1.0 mg ml^–1 significantly decreased it, being cSLN‐C (Compritol‐based) the most toxic and HepG2 the most affected. DNA damage was not significantly increased by 0.1 mg ml^–1 cSLN but damage was observed at 1.0 mg ml^–1 cSLN‐C. Thus, no genotoxicity is to be expected at concentrations that do not reduce cell viability. Copyright © 2013 John Wiley & Sons, Ltd.     

Simultaneous determination of glipizide and glimepride by Rp-Hplc in dosage formulations and in human serum

In this article, simple, liquid chromatographic method has been developed and validated for the determination of glipizide and glimepride in pharmaceutical formulations and in human serum. Chromatographic separation was carried out on a Nucleosil, C₁₈ (10?μm, 25?×?0.46?cm) column using the mobile phase 80:20 methanol:water with pH adjusted to 3.5 at a flow rate 1?ml?min^?1. Peak intensity of the drugs was recorded at 230?nm with UV detection. The linearity of the method was studied over the concentration range of 0.15–5?μg?ml^?1 (r?=?0.9979) and 0.5–7.5?μg?ml^?1 (r?=?0.9988) for glipizide and glimepride, respectively. Detection and quantitation limits were found to be 20 and 46?ng?ml^?1 and 70 and 141?ng?ml^?1 for glipizide and glimepride, respectively. There was no significant interference of extra pharmacopeial ingredients and serum observed in the assay of these two drugs.     

Binding pattern and toxicological effects of lectins from genus Canavalia on bovine sperm

The aim of this study was to determine the binding patterns of Canavalia ensiformis (ConA), Canavalia boliviana (ConBol) and Canavalia brasiliensis (ConBr) lectins to bovine sperm and their effects on sperm motility, viability, lipid peroxidation, reactive oxygen species production and fertilization ability. ConA bound to whole spermatozoa, with the exception of the equatorial segment, ConBol did not interact with the acrosome region and ConBr exhibited a fragmented binding pattern. The three lectins decreased sperm motility but did not affect cell viability or lipid peroxidation. Nevertheless, ROS production was increased in comparison to controls and a reduction in the cleavage and blastocyst ratio was induced in comparison to controls. In conclusion, this study determined that structurally similar lectins interact differently with bovine sperm and affect sperm motility, viability, lipid peroxidation, ROS production and fertilization ability in various ways.     

Skin delivery of epigallocatechin-3-gallate (EGCG) and hyaluronic acid loaded nano-transfersomes for antioxidant and anti-aging effects in UV radiation induced skin damage

The present work attempts to develop and statistically optimize transfersomes containing EGCG and hyaluronic acid to synergize the UV radiation-protective ability of both compounds, along with imparting antioxidant and anti-aging effects. Transfersomes were prepared by thin film hydration technique, using soy phosphatidylcholine and sodium cholate, combined with high-pressure homogenization. They were characterized with respect to size, polydispersity index, zeta potential, morphology, entrapment efficiency, Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), in vitro antioxidant activity and ex vivo skin permeation studies. Cell viability, lipid peroxidation, intracellular ROS levels and expression of MMPs (2 and 9) were determined in human keratinocyte cell lines (HaCaT). The composition of the transfersomes was statistically optimized by Design of Experiments using Box–Behnken design with four factors at three levels. The optimized transfersome formulation showed vesicle size, polydispersity index and zeta potential of 101.2?±?6.0?nm, 0.245?±?0.069 and ?44.8?±?5.24?mV, respectively. FTIR and DSC showed no interaction between EGCG and the selected excipients. XRD results revealed no form conversion of EGCG in its transfersomal form. The optimized transfersomes were found to increase the cell viability and reduce the lipid peroxidation, intracellular ROS and expression of MMPs in HaCaT cells. The optimized transfersomal formulation of EGCG and HA exhibited considerably higher skin permeation and deposition of EGCG than that observed with plain EGCG. The results underline the potential application of the developed transfersomes in sunscreen cream/lotions for improvement of UV radiation-protection along with deriving antioxidant and anti-aging effects.     

Early cellular responses against tributyltin chloride exposure in primary cultures derived from various brain regions

Tributyltin (TBT) is a potent biocide and commonly used in various industrial sectors. Humans are mainly exposed through the food chain. We have previously demonstrated tin accumulation in brain following TBT-chloride (TBTC) exposure. In this study, effect of TBTC on dissociated cells from different brain regions was evaluated. Cytotoxicity assay (MTT), mode of cell death (Annexin V/PI assay), oxidative stress parameters (ROS and lipid peroxidation), reducing power of the cell (GSH), mitochondrial membrane potential (MMP) and intracellular Ca²⁺ were evaluated to ascertain the effect of TBTC. Expression of glial fibrillary acidic protein (GFAP) was measured to understand the effect on astroglial cells. TBTC as low as 30 nM was found to reduce GSH levels, whereas higher doses of 300 and 3000 nM induced ROS generation and marked loss in cell viability mainly through apoptosis. Striatum showed higher susceptibility than other regions, which may have further implications on various neurological aspects.     

Garlic Compounds Protect Vascular Endothelial Cells from Oxidized Low Density Lipoprotein-induced Injury

Oxidation of low density lipoprotein (LDL) has been recognized as playing an important role in the initiation and progression of atherosclerosis. In this study, the effects of aged garlic extract and one of its major compounds, S-allylcysteine, on oxidized LDL-induced cell injury were studied. Pulmonary artery endothelial cells were pre-incubated with the garlic extract (1, 2.5 and 5 mg mL^?) or 5-allylcysteine (01, 1, 10 and 20 mm ) at 37°C and 5% CO₂ for 24 h, washed, and then exposed to 01 mg mL^? oxidized LDL for 24 h. Lactate dehydrogenase release as an index of membrane damage, methylthiazol tetrazolium assay for cell viability and thiobarbituric acid reactive substances indicating lipid peroxidation were determined. Preincubation of endothelial cells with the extract or S-allylcysteine significantly prevented membrane damage, loss of cell viability and lipid peroxidation. The data indicate that these compounds can protect vascular endothelial cells from injury caused by oxidized LDL, and suggest that they may be useful for prevention of atherosclerosis.     

Cellular uptake and toxicity effects of silver nanoparticles in mammalian kidney cells

The rapid progress and early commercial acceptance of silver‐based nanomaterials is owed to their biocidal activity. Besides embracing the antimicrobial potential of silver nanoparticles (AgNPs), it is imperative to give special attention to the potential adverse health effects of nanoparticles owing to prolonged exposure. Here, we report a detailed study on the in vitro interactions of citrate‐coated AgNPs with porcine kidney (Pk15) cells. As uncertainty remains whether biological/cellular responses to AgNPs are solely as a result of the release of silver ions or whether the AgNPs themselves have toxic effects, we investigated the effects of Ag⁺ on Pk15 cells for comparison. Next, we investigated the cellular uptake of both AgNPs and Ag⁺ in Pk15 cells at various concentrations applied. The detected Ag contents in cells exposed to 50 mg l^?1 AgNPs and 50 mg l^?1 Ag⁺ were 209 and 25 µg of Ag per 10⁶ cells, respectively. Transmission electron microscopy (TEM) images indicated that the Pk15 cells internalized AgNPs by endocytosis. Both forms of silver, nano and ionic, decreased the number of viable Pk15 cells after 24 h in a dose‐dependent manner. In spite of a significant uptake into the cells, AgNPs had only insignificant toxicity at concentrations lower than 25 mg l^?1, whereas Ag⁺ exhibited a significant decrease in cell viability at one‐fifth of this concentration. The Comet assay suggested that a rather high concentration of AgNP (above 25 mg l^?1) is able to induce genotoxicity in Pk15 cells. Further studies must seek deeper understanding of AgNP behavior in biological media and their interactions with cellular membranes. Copyright © 2014 John Wiley & Sons, Ltd.     

Plasma concentrations and bioavailability of isosorbide dinitrate and pindolol from a combination formulation

The plasma concentrations and bioavailability of sustained-release isosorbide denigrate and standard-release pindolol have been compared after administration of these drugs in combination and alone. Bioavailability parameters of isosorbide dinitrate and pindolol obtained after administration of the drugs in combination were not significantly different (P>0.05) to those obtained after administration of either drug alone. Two peaks of mean concentrations of isosorbide dinitrate occurred in plasma after administration of 30 mg of this drug in combination with 7.5 mg pindolol (4.4 ng ml^?1 at 1 h and 4.5ng ml^?1 at 5h), or alone (5.9ngml^?1 at 2h and 5.7ng ml^?1 at 5h). In each case, plasma concentrations of isosorbide dinitrate were maintained during at least 8 h, whereas the drug was not detected in plasma at 2.5 h after administration of a standardrelease formulation. The peaks of mean concentrations of pindolol were 39.7ng ml^?1 at l.5h after administration of 7.5 mg drug in combination with isosorbide dinitrate and 38.0 ng ml^?1 at 1 h after administration of the drug alone. Concentrations of pindolol in plasma declined with a half-life of 3 h.     

An alkaline comet assay study on the antimalarial drug atovaquone in human peripheral blood lymphocytes: a study based on clinically relevant concentrations

Atovaquone, a hydroxynaphthoquinone, is an anti‐parasite drug, selectively targeting the mitochondrial respiratory chain of malaria parasite. It is used for both the treatment and prevention of malaria, usually in a fixed combination with proguanil. Although atovaquone has not often been associated with severe adverse reactions in the recommended dosages and has a relatively favorable side effect profile, the present study was undertaken to evaluate its cytogenotoxic potential towards human peripheral blood lymphocytes. Two different concentrations of atovaquone found in plasma when used in fixed‐dose combination with proguanile hydrochloride were used with and without S9 metabolic activation: 2950 ng ml^?1 used for prophylactic treatment and 11 800 ng ml^?1 used in treatment of malaria. The results showed that lymphocyte viability was not affected after the treatment, suggesting that atovaquone was not cytotoxic in the given concentrations. With the alkaline comet assay we demonstrated that in human peripheral blood lymphocytes no significant changes in comet parameters occurred after the treatment. There were no differences in tested parameters with the addition of S9 metabolic activation, indicating that atovaquone either has no metabolite or it is not toxic in the given concentrations. Since no effects were observed after the treatment, it is to be concluded that atovaquone is safe from the aspect of genototoxicity in the recommended dosages. Copyright © 2011 John Wiley & Sons, Ltd.     

Protective effect of captopril against diazinon induced nephrotoxicity and neurotoxicity via inhibition of ROS-NO pathway

Diazinon (Dz) is a widely used insecticide. It can induce nephrotoxicity and neurotoxicity via oxidative stress. Captopril, an angiotensin-converting enzyme inhibitor, is known for its antioxidant properties. In this study, we used captopril for ameliorating of Dz-induced kidney and brain toxicity in rats. Animals were divided into five groups as follows: negative control (olive oil), Dz (150?mg kg^?1), captopril (60 and 100?mg kg^?1) and positive control (N-acetylcysteine 200?mg kg^?1) were injected intraperitoneally 30?min before Dz. After 24?h, animals were anesthetized and the brain and kidney tissues were separated. Then oxidative stress factors were evaluated. Also, blood was collected for assessment of blood urea nitrogen (BUN), creatinine (Cr) and nitric oxide (NO) levels. Dz significantly increased oxidative stress markers such as reactive oxygen species (ROS), lipid peroxidation, and protein carbonyl as well as glutathione (GSH) oxidation in both tissues. Increased levels of the BUN, Cr and NO were observed after Dz injection. Interestingly, captopril administration significantly decreased ROS production in both tissues. Captopril significantly protected kidney and brain against lipid peroxidation and GSH oxidation. Administration of captopril could markedly inhibit protein carbonyl production in kidney and brain after Dz injection. Furthermore, captopril ameliorated the increased level of BUN, Cr and NO. These results suggested that captopril can prevent Dz-induced oxidative stress, nephrotoxicity and neurotoxicity because of its antioxidant activity.     

Cumene hydroperoxide-mediated lipid peroxidation in rat alveolar macrophages following induction of phospholipidosis with chlorphentermine

Rats were treated for 4 weeks with chlorphentermine hydrochloride (30 mg/kg, i.p., 5 days/week), a regiment which causes a profound phospholipidosis in the alveolar macrophages (AMs). The susceptibility of these lipid-laden cells to lipid peroxidation was examined and compared to AMs from control (untreated) rats. Lipid peroxidation was induced in cells in vitro by incubation with cumene hydroperoxide (10^?5 M?10^?3 M). A dose dependent increase in malonyl dialdehyde (MDA) formation was observed with both populations of AMs. Two to three times more MDA was found in lipidotic AMs than controls at the higher dose of cumene hydroperoxide. Under these conditions, less loss of cellular viability resulted with the lipidotic AMs than controls. The partial depletion of reduced glutathione in the cells led to an even greater MDA formation by both cell-types with the lipidotic AMs being more markedly affected. Both populations of AMs experienced a greater loss of viability associated with loss of reduced glutathione with the control AMs showing more toxicity than the lipidotic cells. Therefore, while the induction of phospholipidosis renders AMs more susceptible to lipid peroxidation, they show less of a loss in cellular viability than control cells. The previously reported augmentation in the antioxidant defense mechanisms in the lipidotic cells may be partially responsible for these results.     

Copper-induced oxidative stress in rainbow trout gill cells

Copper is known to pose a serious threat to aquatic organisms. However, the mechanisms of its toxicity still remain unclear. Cu is known to exert its toxicity partly due to the formation of reactive oxygen species (ROS). The purpose of this work was therefore to link the exposure to copper at pH 6 and 7 to cellular formation of ROS and effects like cell viability and genotoxicity using the rainbow trout gill cell line RTgill-W1. To relate effects to bioavailable copper, free Cu(2+) concentrations in the medium were calculated using the programm ChemEQL 3.0. 2',7'-Dichlorodihydrofluorescein-diacetate (H(2)DCF-DA) was used as cell-permeant indicator of ROS formation. Cell viability was assessed using the fluorogenic probe 5-carboxyfluorescein diacetate acetoxymethyl ester (CFDA-AM). DNA strand breaks were assessed using the comet assay, and lipid peroxidation was investigated using the thiobarbituric acid-reactive substances assay (TBARS). Copper treatment resulted in a dose-dependent elevation in cytotoxicity and formation of cellular ROS. Cell viability was significantly reduced at total copper (Cu(T)) concentrations of 5 microM (corresponding to a free Cu(2+) of 0.11 microM at pH 7) and higher, resulting in an EC(50) of Cu(T)=29.2 microM (Cu(2+)=0.63 microM, pH 7). Neither an impairment concerning the viability of control cells due to growth at pH 6 was observed nor significant differences for cytotoxicity in cells exposed to the same nominal Cu(T) concentrations at pH 6 compared to pH 7. Cellular ROS concentrations increased significantly and decreased with loss of cell viability. After normalizing ROS formation to cell viability, ROS induction up to 25-35-fold compared to the control was detected, but mainly for rather high concentrations (Cu(T) > or = 100 microM; Cu(2+) > or = 2.2 microM, pH 7). ROS formation rates were slightly higher when cells were exposed to Cu at pH 6 compared to pH 7, correlating with the higher free Cu(2+) concentrations. A significant induction of DNA strand breaks was noted at Cu(T) of 1 and 2.5 microM with greater effects at pH 6 due to higher free Cu(2+) concentrations than at pH 7. No effects on lipid peroxidation were observed. These results lead to the hypothesis that copper-induced loss in viability and genotoxicity in trout gill cells are partially triggered by the generation of ROS and related to the free Cu(2+).     

Identification and quantification of metabolites of arachidonic acid from cultures of endothelial cells by HPLC-MS2

Epoxyeicosatrienoic acids (EETs) and hydroxyeicosatetraenoic acids (HETEs) are oxidative products of arachidonic acid, some of which participate in the regulation of vascular tone. Little is known about the production of EETs and HETEs in cultures of endothelial cells. This paper reports an assay for the simultaneous quantification of isomers of EETs and HETEs from endothelial cell culture supernatants by employing solid-phase extraction and liquid chromatography-mass spectrometry. The method enabled measurement of 5,6-EET, 8,9-EET, 11,12-EET, 14,15-EET, 5-HETE, 8-HETE, 11-HETE, 12-HETE and 15-HETE. The metabolites were chromatographically separated by reversed-phase HPLC and identified by negative ESI tandem mass spectrometry and this method was used to investigate the metabolism of arachidonic acid with an endothelial cell line. For quantification, the sum of signal intensities of characteristic fragment ions was used. The detection limits for 5,6-EET and of other EET and HETE isomers were 2.0, 0.64 and 8?ng?ml^?1 culture medium, respectively. The precision of the method was determined with spiked culture medium (three concentrations, n?=?5) and the average RSD ranged from 6.0 to 24.2%. The dynamic range was 0.6–23.5?ng?ml^?1 culture medium for EETs and 8.0–200?ng?ml^?1 for HETEs. Arachidonic acid was mainly metabolised to HETEs with product levels ranging from 59.3 to 460?ng 10^?6 cells. The median of 8,9-EET and 14,15-EET was 14.5 and 17.7?ng 10^?6 cells, respectively, whereas 5,6-EET and 11,12-EET were below 2?ng 10^?6 cells in a 5-min incubation assay at a 30?µM arachidonic acid substrate concentration.     

Physiologically based modeling of p‐tert‐octylphenol kinetics following intravenous,oral or subcutaneous exposure in male and female Sprague–Dawley rats

The objective of this study was to develop a physiologically based pharmacokinetic (PBPK) model for p‐tert‐octylphenol (OP) for understanding the qualitative and quantitative determinants of its kinetics in Sprague–Dawley rats. Compartments of the PBPK model included the liver, richly perfused tissues, poorly perfused tissues, reproductive tissues, adipose tissue and subcutaneous space, in which OP uptake was described as a blood flow‐ or a membrane diffusion‐limited process. The PBPK model successfully simulated previously published data on blood and tissue OP concentrations in Sprague–Dawley rats following oral, intravenous (i.v.) or subcutaneous (s.c.) routes. The model predicted that OP concentrations would reach 6.8, 13.8 and 27.9 ng ml^?1 (male) and 7.2, 14.7 and 31.4 ng ml^?1 (female), 4 h after a single i.v. dose of 2, 4 and 8 mg kg^?1, respectively. The model also predicted that OP concentrations would reach 53.3, 134.8 and 271.2 ng ml^?1 (male) and 87.4, 221.4 and 449.7 ng ml^?1 (female) 4 h after a single oral dose (50, 125 and 250 mg kg^?1) and that, 4 h after a single s.c. dose (125 mg kg^?1), OP concentrations would reach 111.3 ng ml^?1 (male) and 121.6 ng ml^?1. A marked sex difference was seen in blood and tissue OP concentrations. This was reflected in the model by a gender‐specific maximal velocity of metabolism (V_max) that was higher (1.77×) in male than in female rats. Further studies are required to elucidate the mechanism underlying the gender differences and to evaluate whether that is also observed in humans. Copyright © 2010 John Wiley & Sons, Ltd.     

Radioimmunoassay of the new opiate analgesics alfentanil and sufentanil. Preliminary pharmacokinetic profile in man

The development of two analogous radioimmunoassay (RIA) procedures based on dextran-charcoal separation is described for the quantification of two fentanyl-like analgesics, alfentanil and sufentanil. Immunization of rabbits with conjugates of bovine serum albumin and carboxy-derivatives of the respective drugs resulted in the production of antisera capable of detecting less than 0.05 ng ml^?1 of the parent analgesics with high specificity and almost no cross-reactivity with major metabolites. Excellent agreement was obtained between RIA—without prior extraction—and gas chromatography for alfentanil concentrations in human plasma. Because of sufentanil's low therapeutic plasma levels, no comparison could be made between its RIA and an alternative assay, however, there was strong evidence for the specificity of the assay when applied directly to plasma. With these RIA methods preliminary information was obtained on plasma concentrations and elimination of alfentanil or sufentanil in patients given an intravenous bolus injection of 50 μg kg^?1 of alfentanil, or 5 μg kg^?1 of sufentanil. For both analgesics, the pharmacokinetic profile in man could be described by a three-compartment model. The terminal elimination half-life was 88 min for alfentanil and 140 min for sufentanil. Six hours after a therapeutic dose, plasma levels were in the order of 3 and 0.3 ng ml^?1 for alfentanil and sufentanil respectively.