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PubMed2005

Solid state characteristics of ternary solid dispersions composed of PVP VA64, Myrj 52 and itraconazole.

The purpose of the present study was to characterize the solid state properties of ternary solid dispersions made up of PVP VA64, Myrj 52 and itraconazole. The solid dispersions were prepared by dissolving the materials in methylene chloride, followed by evaporation under reduced pressure of the solvent at 55 degrees C in a rotovapor. Binary and ternary solid dispersions were characterized by standard and modulated temperature differential scanning calorimetry and X-ray powder diffraction. Although PVP VA64 and itraconazole were found to be completely miscible in the solid state, addition of a small amount of Myrj 52 to the drug-polymer system leads to separation of itraconazole thus demonstrating that Myrj 52 expels the drug from the polymer phase.

Antifungal Agents↗
PubMed2004

Poly(vinylpyrrolidone-co-dimethyl maleic acid) as a novel renal targeting carrier.

Poly(vinylpyrrolidone-co-dimethyl maleic acid) (PVD) was found to have high renal-targeting capability and safety as a drug carrier. To optimize the renal drug delivery system using PVD, the relationship between the molecular weight of PVD and its renal accumulation were evaluated in mice by their intravenous injection. It was found that the molecular size of 6-8 kDa was associated with the highest renal accumulation. The specific bioactivity of PVD-conjugated superoxide dismutase (SOD) relative to that of unmodified SOD gradually decreased with an increase in the degree of modification to SOD with PVD6K. The conjugated SOD (L-PVD-SOD) with the molecular size of 73 kDa, which had comparable specific bioactivity with native SOD, showed longer plasma half-life than native SOD. About sixfold more L-PVD-SOD was distributed to the kidneys than native SOD 3 h after intravenous injection, whereas extensive PVD modification did not enhance the renal accumulation of SOD. This L-PVD-SOD effectively accelerated recovery from mercuric chloride-induced acute renal failure in vivo. These results suggest that L-PVD-SOD may be the optimal derivative as a potential therapeutic agent to various renal diseases.

Acute Kidney Injury↗
PubMed2005

Bioavailability of nerodilol-based transdermal therapeutic system of nicorandil in human volunteers.

The objective of the present investigation was to design and evaluate a nerodilol-based transdermal therapeutic system (TTS) for finding its ability in providing the desired steady-state plasma concentration of nicorandil in human volunteers. The influence of EVA2825 membrane, adhesive-coated EVA2825 membrane and adhesive-coated EVA2825-rat skin composite on the in vitro permeation of nicorandil from a nerodilol-based HPMC gel drug reservoir was studied against a control (excised rat skin alone). The flux of nicorandil from the nerodilol-based HMPC drug reservoir across excised rat skin (control) was 384.0+/-4.6 microg/cm2 h and this decreased to 222.7+/-7.1 microg/cm2 h when studied across EVA2825 membrane indicating that EVA2825 membrane was effective as rate controlling membrane. The flux of the drug decreased to 183.8+/-5.7 microg/cm2 h on application of a water-based acrylic adhesive (TACKWHITE A 4MED) coat to EVA2825 membrane. However, the flux of nicorandil across adhesive-coated EVA2825-membrane-rat-skin composite was 164.8+/-1.8 microg/cm2 h, which was 1.74-times of the required flux that prompted for preparation of TTS. The nerodilol-based drug reservoir system was sandwiched between a composite of adhesive-coated EVA2825 membrane-release liner and a backing membrane. The resultant sandwich was heat-sealed to produce circle-shaped TTS (20 cm2) that were subjected to bioavailability study in human volunteers against immediate release nicorandil tablet. The nerodilol-based TTS provided a steady-state plasma concentration of 25.5 ng/ml for 24 h in human volunteers. It was concluded that the nerodilol-based TTS of nicorandil provided the desired plasma concentration of the drug for the predetermined period of time with minimal fluctuations.

Administration, Cutaneous↗
PubMed2004

Poly(ethylene glycol dimethacrylate-n-vinyl imidazole) beads for heavy metal removal.

Poly(ethylene glycol dimethacrylate-n-vinyl imidazole) [poly(EGDMA-VIM)] hydrogel (average diameter 150-200 microm) was prepared by copolymerizing ethylene glycol dimethacrylate (EGDMA) with n-vinyl imidazole (VIM). The copolymer hydrogel bead composition was characterized by elemental analysis and found to contain 5 EGDMA monomer units each VIM monomer unit. Poly(EGDMA-VIM) beads had a specific surface area of 59.8 m2/g. Poly(EGDMA-VIM) beads were characterized by swelling studies and scanning electron microscopy (SEM). These poly(EGDMA-VIM) beads with a swelling ratio of 78% were used for the heavy metal removal studies. Chelation capacity of the beads for the selected metal ions, i.e., Cd(II), Hg(II) and Pb(II) were investigated in aqueous media containing different amounts of these ions (10-750 mg/l) and at different pH values (3.0-7.0). Chelation rate was very fast. The maximum chelation capacities of the poly(EGDMA-VIM) beads were 69.4 mg/g for Cd(II), 114.8 mg/g for Pb(II) and 163.5 mg/g for Hg(II). The affinity order on molar basis was observed as follows: Hg(II) > Cd(II) > Pb(II). Chelation behavior of heavy metal ions could be modelled using both the Langmuir and Freundlich isotherms. pH significantly affected the chelation capacity of VIM incorporated beads. Chelation of heavy metal ions from synthetic wastewater was also studied. The chelation capacities are 45.6 mg/g for Cd(II), 74.2 mg/g for Hg(II) and 92.5 mg/g for Pb(II) at 0.5 mmol/l initial metal concentration. Regeneration of the chelating-beads was easily performed with 0.1 M HNO3. These features make poly(EGDMA-VIM) beads potential candidate adsorbent for heavy metal removal.

Acrylates↗
PubMed2006

On-line arsenic co-precipitation on ethyl vinyl acetate turning-packed mini-column followed by hydride generation-ICP OES determination.

An alternative and new system for on-line preconcentration of arsenic by sorption on a mini-column associated to hydride generation--inductively coupled plasma--optical emission spectrometry determination was studied. It is based on the sorption of arsenic on a column packed with ethyl vinyl acetate (EVA) turnings and the use of La(III) as co-precipitant reagent. This polymeric material was employed here for the first time as filling material for column preconcentration. It could work both as adsorbent and as sieve material. Sample and co-precipitant agent (lanthanum nitrate) were off-line mixed and merged with ammonium buffer solution (pH 10.0), which promoted precipitation and quantitative collection on the small EVA turnings. The arsenic preconcentrated by co-precipitation with lanthanum hydroxide precipitate was subsequently eluted with hydrochloric acid, which was the medium used for hydride generation. Considering a flow rate of 5 ml/min, three enrichment factors were obtained, 28-, 38- and 45-fold at three different sampling times, 60, 120 and 180s; respectively. The detection limits (3s) obtained for each case were 0.013, 0.009 and 0.007 microg/l. Additionally, the calculated precisions expressed as relatively standard deviation (R.S.D.) were 0.9, 1.3 and 1.1%. Satisfactory results were obtained for the determination of arsenic in standard reference material NIST 1643e Trace Elements in Water and drinking water samples.

Arsenic↗
PubMed2005

HPLC determination of lincomycin in premixes and feedstuffs with solid-phase extraction on HLB OASIS and LC-MS/MS confirmation.

A rapid clean-up procedure based on solid-phase extraction (SPE) and HPLC determination of lincomycin in premixes with UV detection is described. After extraction of lincomycin from premix with extraction solvent the extract is applied to OASIS HLB column treated with methanol and water. Lincomycin is eluted with methanol and effluent is analysed on analytical column (phenyl) using mobile phase consists 0.2% phosphoric acid in water and acetonitrile (875:125, v/v). Detection is performed at 208 nm. Quantitation is carried out using external standard. The mean recovery of lincomycin was 105.0+/-7.3%, in concentration range of 250-750 mg kg(-1), and 99.8+/-3.7%, in concentration range of 10,000-150,000 mg kg(-1). The limit of determination, based on a signal-to-noise ratio of 10:1, was 5.2 mg kg(-1). LC-MS/MS confirmation of lincomycin is also presented. Identification was performed by monitoring two pairs of multiple reaction monitoring ions from the parent ions (m/z 407.2-->126.1 and 407.2-->359.2) at the defined retention time window and by matching of the specific tolerance of relative abundance of major ions as stated in the European Union Commission Decision 2002/657/EC.

Animal Feed↗
PubMed2005

Liquid chromatographic assay of ivermectin in human plasma for application to clinical pharmacokinetic studies.

There is a need for an accurate, sensitive and selective high-performance liquid chromatography (HPLC) method for the quantitation of ivermectin in human plasma that separates the parent drug from metabolites. Ivermectin and the internal standard, moxidectin, were extracted from 0.2 ml of human plasma using Oasis HLB solid phase extraction cartridges. After extraction, fluorescent derivatives of ivermectin and moxidectin were made by reaction with trifluoroacetic anhydride and N-methylimidazole. Separation was achieved on a Alltech Ultrasphere C18 5mu column with a mobile phase composed of tetrahydrofuran-acetonitrile-water (40:38:22 v/v/v). Detection is by fluorescence, with an excitation of 365 nm and emission of 475 nm. The retention times of ivermectin and internal standard, moxidectin are approximately 24.5 and 12.5 min, respectively. The assay is linear over the concentration range of 0.2-200 ng/ml of ivermectin in human plasma (r = 0.9992, weighted by 1/concentration). Recoveries of ivermectin are greater than 80% at all concentrations. The analysis of quality control samples for ivermectin 0.2, 25, and 200 ng/ml demonstrated excellent precision with coefficient of variation of 6.1, 3.6 and 2.3%, respectively (n = 6). The method is accurate with all intra-day (n = 6) and interday (n = 12) mean concentration within 10% of nominal values at all quality control sample concentrations. Storage stability for 30 days at -80 degrees C and after three freeze-thaw cycles are within acceptable limits. The method separates ivermectin from multiple less and more polar unidentified metabolites. This method is robust and suitable for clinical pharmacokinetic studies. The analytical procedure has been applied to a pharmacokinetic study of ivermectin in healthy volunteers and to the analysis of plasma specimens from patients with disseminated strongyloidiasis.

Antiparasitic Agents↗
PubMed2004

Initiation of delayed ovotoxicity by in vitro and in vivo exposures of rat ovaries to 4-vinylcyclohexene diepoxide.

Repeated daily dosing of rats with the ovotoxic, occupational chemical 4-vinylcyclohexene diepoxide (VCD, 80 mg/kg, i.p.) selectively depletes primordial and primary ovarian follicles. This study was designed to investigate whether follicle loss can be achieved following a single, acute exposure to VCD. Ovaries removed from postnatal-day-4 female Fischer 344 rats were cultured in the absence or presence of VCD for 15 days. Continuous in vitro exposure to VCD (15 days) caused concentration-dependent loss of primordial and small primary follicles. A single exposure to VCD in vitro (30 microM, 24 h) also caused significant losses of primordial and primary follicles 14 days later. Additionally, 28-day-old female rats were given a single injection of VCD (40-320 mg/kg, i.p.). A single dose at 320 mg/kg resulted in substantial loss of all follicle stages beginning 6 days later. Overall, these results demonstrate that an acute exposure to high concentrations/doses of VCD is sufficient to cause subsequent delayed loss of follicles.

Animals↗
PubMed2005

Differences between rats and mice in the involvement of the aryl hydrocarbon receptor in 4-vinylcyclohexene diepoxide-induced ovarian follicle loss.

Repeated dosing with the occupational chemical 4-vinylcyclohexene diepoxide (VCD) selectively depletes small pre-antral follicles in the ovaries of rats and mice via apoptosis. The aryl hydrocarbon receptor (AhR) plays a role in mediating the effects of several xenobiotics. Therefore, this study was designed to investigate a potential role of the AhR in VCD-induced ovotoxicity. Female F344 rats, C57BL/6 mice, or AhR-deficient (-/-, AhRKO) mice were dosed daily (15 days) with vehicle, VCD (80 mg/kg, i.p.) and/or the AhR antagonist, alpha-naphthoflavone (ANF; 80 mg/kg, i.p.). Compared with controls, VCD caused a 60% reduction (P < 0.05) in primordial and primary follicles in mice and rats. Concurrent dosing with ANF protected against the VCD-induced follicle loss in rats, but not in mice. As with AhR-intact mice and rats, VCD induced a 70% loss (P < 0.05) of small pre-antral follicles in AhRKO mice. AhR mRNA expression was increased (P < 0.05) by VCD dosing in small pre-antral follicles isolated from ovaries of rats but not mice. AhR protein in rats was increased by VCD dosing in oocyte nuclei in primordial and primary follicles when measured by immunofluorescence and confocal microscopy. In rat small pre-antral follicles, apoptosis-associated caspase-3-like activity was increased (P < 0.05) by VCD treatment, decreased (P < 0.05) by ANF treatment, and unaffected by VCD plus ANF treatment. VCD had no effect on expression of GST Ya1 or GST Ya2 mRNA or CYP 1A1 protein in rats. Taken together, these findings demonstrate a difference between rats and mice in the potential involvement of AhR as related to VCD-induced ovotoxicity. Whereas, AhR appears to be involved in rats, no evidence for a similar role in mice was obtained. Overall, these findings point out that there can be mechanistic species differences in ovarian responses to xenobiotic chemicals.

Animals↗
PubMed2003

A site-specific polymeric drug carrier for renal disease treatment.

A well-designed polymeric carrier for site-specific drug delivery in the treatment of renal disease has been reported recently. Approximately 80% of the water-soluble polymer poly(vinylpyrrolidone-co-dimethyl maleic anhydride selectively accumulated in the kidney of mice 24 h after intravenous injection. The detailed mechanism of such selective accumulation is not clear but an energy-dependent process, other than endocytosis, might be involved in the uptake of the polymer. This study is the first to report active targeting using a synthetic polymeric drug carrier.

Animals↗
PubMed2005

Vinyl acetate induces intracellular acidification in mouse oral buccal epithelial cells.

Vinyl acetate exposure in drinking water has been associated with tumor formation in the upper gastrointestinal tract of rats and mice. One potential mechanism for inducing carcinogenesis involves acidification of the intracellular environment due to the metabolism of vinyl acetate to acetic acid. Prolonged intracellular acidification is thought to produce cytotoxic and/or mitogenic responses that are the sentinel pharmacodynamic steps toward cancer. To determine whether exposure to vinyl acetate affects the intracellular pH of intact oral cavity tissue, isolated mouse oral buccal epithelium was loaded with the pH-sensitive dye BCECF, and then exposed to vinyl acetate concentrations ranging from 10 to 1000 microM for up to 4 min. Extracellular vinyl acetate exposure induced a progressive intracellular acidification that was reversible upon removal of the vinyl acetate. The rate of the acidification was concentration-dependent and increased exponentially within the concentration range tested. The magnitude of the vinyl acetate-induced acidification was inhibited by pretreatment with the carboxylesterase inhibitor bis(p-nitrophenyl)phosphate. These results are consistent with the hypothesis that vinyl acetate contributes to the generation and progression of oral cavity tumors via a process of intracellular acidification. Such a process has been proposed to have practical dose-response thresholds below which the intracellular environment can be maintained within homeostatic bounds and the contribution of exposure to carcinogenic risk is negligible.

Acids↗
PubMed1990

Saturation transfer electron spin resonance of Ca2(+)-ATPase covalently spin-labeled with beta-substituted vinyl ketone- and maleimide-nitroxide derivatives. Effects of segmental motion and labeling levels.

The Ca2(+)-ATPase in native sarcoplasmic reticulum membranes was selectively spin-labeled for saturation transfer electron spin resonance (ESR) studies by prelabeling with N-ethylmaleimide and by using low label/protein ratios. Results with the nitroxide derivative of the standard sulphydryl-modifying reagent, maleimide, were compared with a series of six novel nitroxide beta-substituted vinyl aryl ketone derivatives which differed (with two exceptions) in the substituent at the ketone position. The two exceptions had a different electron withdrawing group at the alpha-carbon, to enhance further the electrophilic character of the beta-carbon. Although differing in their reactivity, all the conjugated unsaturated ketone nitroxide derivatives displayed saturation transfer ESR spectra indicative of much slower motion than did the maleimide derivative. The saturation transfer ESR spectra of maleimide-labeled Ca2(+)-ATPase therefore most likely contain substantial contributions from segmental motion of the labeled group. The effects of the level of spin labeling were also investigated. With increasing degree of spin label incorporation, the linewidths of the conventional ESR spectrum progressively increased and the intensity of the saturation transfer spectrum dropped dramatically, as a result of increasing spin-spin interactions. The hyperfine splittings of the conventional spectrum and the outer lineheight ratios of the saturation transfer spectrum remained relatively unchanged. Extrapolation back to zero labeling level yielded comparable values for the effective rotational correlation times deduced from the saturation transfer spectrum intensities and from the lineheight ratios, for the vinyl ketone label. For the maleimide label the extrapolated values from the integral are significantly lower than those from the lineheight ratios, probably because of the segmental motion. Comparison is made of the effective rotational correlation time for the vinyl ketone label with the predictions of hydrodynamic models for the protein diffusion, in a discussion of the aggregation state of the Ca2(+)-ATPase in the native sarcoplasmic reticulum membrane. The implications for the study of protein rotational diffusion and segmental motion, and of the proximity relationships between labeled groups, using saturation transfer ESR spectroscopy are discussed.

Animals↗