Covalent organic nanospheres modified magnetic nanoparticles for extraction of blood lipid regulators in water samples.

Covalent organic nanospheres are new kind of nanospherical polymer with large specific surface area, uniform morphology, and excellent chemical and thermal stability. This material can be fabricated by a facile and rapid room temperature solution-phase strategy. In this work, magnetic nanoparticles were attached to the surface of covalent organic nanospheres, and the obtained composites were used for the extraction of blood lipid regulators such as clofibrate and fenofibrate. These composites were characterized with Fourier-transformed infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. Several parameters that might affect the extraction efficiency including acetonitrile content, pH value, extraction time, and sample volume were investigated. Under optimum conditions, the proposed analytical method showed high extraction efficiency toward clofibrate and fenofibrate with enrichment factors between 60 and 83. This method exhibited outstanding analytical performance with wide linear range and excellent reproducibility and had low limits of detection in the range of 0.02-0.03 ng/mL. This method was also applied to the detection of clofibrate and fenofibrate in lake water samples, and good recoveries in the range of 92.6-112.6% was obtained.

Acute kidney disease and acute kidney injury biomarkers in coronary care unit patients.

BACKGROUND: Acute kidney disease (AKD) describes acute or subacute damage and/or loss of kidney function for a duration of between 7 and 90 days after exposure to an acute kidney injury (AKI) initiating event. This study investigated the predictive ability of AKI biomarkers in predicting AKD in coronary care unit (CCU) patients. METHODS: A total of 269 (mean age: 64 years; 202 (75%) men and 67 (25%) women) patients admitted to the CCU of a tertiary care teaching hospital from November 2009 to September 2014 were enrolled. Information considered necessary to evaluate 31 demographic, clinical and laboratory variables (including AKI biomarkers) was prospectively recorded on the first day of CCU admission for post hoc analysis as predictors of AKD. Blood and urinary samples of the enrolled patients were tested for neutrophil gelatinase-associated lipocalin (NGAL), cystatin C (CysC) and interleukin-18 (IL-18). RESULTS: The overall hospital mortality rate was 4.8%. Of the 269 patients, 128 (47.6%) had AKD. Multivariate logistic regression analysis revealed that age, hemoglobin, ejection fraction and serum IL-18 were independent predictors of AKD. Cumulative survival rates at 5 years of follow-up after hospital discharge differed significantly (p < 0.001) between subgroups of patients diagnosed with AKD (stage 0A, 0C, 1, 2 and 3). The overall 5-year survival rate was 81.8% (220/269). Multivariate Cox proportional hazard analysis revealed that urine NGAL, body weight and hemoglobin level were independent risk factors for 5-year mortality. CONCLUSIONS: This investigation confirmed that AKI biomarkers can predict AKD in CCU patients. Age, hemoglobin, ejection fraction and serum IL-18 were independently associated with developing AKD in the CCU patients, and urine NGAL, body weight and hemoglobin level could predict 5-year survival in these patients.

Synthesis of highly water-soluble fibrate derivatives via BGLation.

Three water-soluble fibrates (fenofibrate, bezafibrate and chlofibrate) conjugated with a symmetrically branched glyceryl trimer (BGL003) were synthesized, and an evaluation of the fenofibrate-BGL003 conjugate as a candidate for anti-hyperlipemia drug was carried out using rats. The water-solubility of the fenofibrate-BGL003 conjugate was several thousand times greater than that of the original fenofibrate. The lipid-lowering effects of the fenofibrate-BGL003 conjugate were as strong as those of the same grams of fenofibrate. The actual active species of fenofibrate, fenofibric acid, was detected in rats' blood, but neither the fenofibrate-BGL003 conjugate nor fenofibrate was detected, probably due to enzymatic hydrolysis of the ester bond. The plasma concentration of fenofibric acid derived from the fenofibrate-BGL003 conjugate was five times higher than that derived from fenofibrate 4h after administration.

Pharmacokinetics of drugs in patients with the nephrotic syndrome.

Since the binding of drugs to plasma proteins can significantly after the intensity of pharmacological and toxicological effects of drugs, we studied the pharmacokinetics of three drugs in patients with hypoalbuminemia secondary to the nephrotic syndrome, but with relatively normal renal function. No significant differences were seen in the pharmacokinetic parameters observed for antipyrine, a drug which is less than 10% bound to plasms proteins. The percentage of unbound diphenylhydantoin, a highly plasms protein-bound drug, was found in patients with the nephrotic syndrome to be twice that of healthy individuals (19,2 vs. 10.1%, P smaller than 0.001). However, there was also a lower steady-state plasma concentration of diphenylhydantoin (2.9 plus or minus 0.6 vs. 6.8 plus or minus 0.6 mug/ml, P smaller than 0.001) secondary to an increase in the plasms clearance (0.048 plus or minus 0.019 vs. 0.022 plus or minus 0.006 liter/kg.h, P smaller than 0.001) in the nephrotic patients. The net effect is no difference in the absolute concentration of unbound diphenylhydantoin in healthy individuals (0.69 plus or minus 0.05 mug/ml) and patients with the nephrotic syndrome (0.59 plus or minus 0.06 mug/ml). Qualitatively, similar differences were observed with clofibrate. The dose of these drugs need not be routinely reduced in patients with the nephrotic syndrome as long as they have reasonably normal renal function (creatinine clearance greater than 50 ml/min). With all highly bound acidic drugs, knowledge of the concentration of unbound drug is essential to the proper interpretation of total blood levels and subsequent treatment of the patient.

Modulation of fatty acid metabolism by glucagon in man. III. Role of pharmacologic limitation of FFA availability.

This study was undertaken to examine the contribution of plasma free fatty acid availability upon the regulation of ketone body and endogenous triglyceride concentration in man. This substrate-product relationship was examined both in the basal state and during hormonally induced ketogenic stimulation. Five insulin-deficient diabetics receiving a fixed dose of exogenous insulin were studied after a twelve-hour fast and twenty-four hours after their last therapeutic insulin injection. Reduction in basal free fatty acid concentration was induced with two weeks of clofibrate administration, and hormonal ketogenic stimulation was induced with glucagon administration. A highly significant correlation was observed between the basal free fatty acid level and the basal ketone body concentration. This substrate-product relationship persisted throughout hormonally induced ketogenic stimulation, suggesting that the basal free fatty acid concentration is a major determinant of the plasma ketone body concentration in man. In contrast, alterations in basal free fatty acid concentration were not accompanied by consistent changes in plasma triglyceride concentration, suggesting that plasma free fatty acid concentration may not be the principal determinant of the endogenous triglyceride concentration in clofibrate-treated diabetic man.

Fluorescence labeling method for aryl halides with 4-(4,5-diphenyl-1H-imidazol-2-yl)phenylboronic acid based on Suzuki coupling reaction.

For the first time, fluorescence labeling methods for aryl halides with a fluorescent arylboronic acid was developed on the basis of a Suzuki coupling reaction. 4-(4,5-diphenyl-lH-imidazol-2-yl)phenylboronic acid (DPA) was used as a fluorescence labeling reagent. In order to explore its analytical performance, the reaction conditions were optimized using simple bromobenzene derivatives. The reactivity was then investigated with chloro- and iodobenzene derivatives, and also bromobenzene derivatives with different position of substituents. The order of reactivity with DPA: iodobenzene > bromobenzene more more than chlorobenzene derivatives, and p- > m- > o-substituted bromobenzenes. The detection limits of bromobenzene, 4-bromotoluene, and 4-bromoanisole ranged from 0.2 to 1.4 pmol/injection at a signal-to-noise ratio, (S/N) of 3. The applicability of the method to biological samples was also evaluated using clofibrate as the analyte. The reaction was found not only to proceed well but also to be selective for clofibrate even in the presence of plasma components. The method allowed the sensitive detection of clofibrate in human plasma with the detection limit of 170 pmol/mL (260 fmol/injection) at a S/N = 3. The proposed method is highly selective and sensitive and thus would be useful for labeling of aryl halides that do not have other functional groups that could be labeled by currently available fluorescent labeling reagents.

Control of clofibrate toxicity in uremic hypertriglyceridemia.

A daily dose of 1.5 to 2.0 gm of clofibrate lowers serum triglyceride (TG) levels in patients with normal renal function but causes muscle toxicity and elevated creatine phosphokinase (CPK) levels in patients with long-term renal failure. Plasma clofibrate disappearance is prolonged as much as seven times normal in severely uremic patients. A marked reduction in the standard 14 gm/wk clofibrate dose to a total dose of 1.0 to 1.5 gm/wk effectively lowered serum TG levels (--28%, p less than 0.02) in hypertriglyceridemic hemodialysis patients without toxicity. The serum clofibrate level at this dose was comparable to that in hypertriglyceridemic nonuremic patients receiving 14 gm/wk of clofibrate. The dose of clofibrate administered to hemodialysis patients can be adjusted to avoid toxicity and provide the desired therapeutic effect by monitoring serum CPK and TG levels.

Effect of clofibrate on the chiral inversion of ibuprofen in healthy volunteers.

OBJECTIVES: To determine the influence of the hypolipidemic drug clofibrate on the stereoselective metabolism of ibuprofen in humans. METHODS: Healthy male subjects (n = 12) ingested a dose of 400 mg pseudoracemic ibuprofen (200 mg R-ibuprofen, 160 mg S-ibuprofen, and 40 mg 13C-S-ibuprofen) on two occasions after either pretreatment with clofibrate (2 gm/day over 1 week) or no pretreatment in a randomized order. RESULTS: When subjects were pretreated with clofibrate, clearances of R-ibuprofen and 13C-S-ibuprofen increased significantly from 55.0 and 66.4 ml/min to 186.2 and 106.7 ml/min (p < 0.01), respectively. This increase was similarly reflected in the clearance by inversion of R-ibuprofen (control, 36.0 ml/min; treated, 118.8 ml/min; p < 0.01), as well as in the clearance by noninversion (control, 19.0 ml/min; treated, 67.4 ml/min; p < 0.01). Unbound clearance values significantly increased for R-ibuprofen (control, 19.5 L/min; treated, 38.7 L/min) but not for 13C-S-ibuprofen (11.8 versus 10.6 L/min, respectively). The fractional inversion of ibuprofen calculated from the urinary metabolite data was increased after clofibrate pretreatment (clofibrate group, 66.4%; control, 53.5%; p < 0.01). However, this was not evident when fractional inversion was calculated from the plasma concentration-time data for the unmetabolized drug. CONCLUSIONS: Clofibrate altered the stereoselective disposition of ibuprofen in healthy volunteers by increased formation of R-ibuprofenoyl-coenzyme A rather than by an effect on oxidative metabolism of ibuprofen. This interaction has potential therapeutic implications.

The concentration of high density lipoprotein in patients with type IV hyperlipoproteinemia and the effect of clofibrate.

Lipid and lipoprotein concentrations, including high density lipoproteins (HDL) and its subfractions, were contrasted in subjects with Type IV hyperlipoproteinemia, before and after therapy with clofibrate. Very low density lipoprotein (VLDL) levels were raised, whereas both low density lipoprotein (LDL) and HDL values were reduced in the patient group. Clofibrate reversed this trend and VLDL cholesterol and protein levels fell to approximate control values. LDL and HDL cholesterol increased but remained significantly lower than in normal controls. However, LDL and HDL protein did approach control values. Of the HDL subfractions, HDL-3 was significantly reduced in the group with Type IV hyperlipoproteinemia. Clofibrate resulted in a significant increase in the HDL-2: HDL-3 cholesterol ratio, but had only a modest effect on HDL-3 concentrations. HDL-3 may be the critical HDL subfraction responsible for the inverse correlation between levels of HDL and the development of ischemic heart disease.

Pharmacokinetics of clofibrate in familial hypercholesterolemia.

Some patients with familial hypercholesterolemia (FHC, type II) are highly responsive to the cholesterol-lowering effect of clofibrate, while others are not only resistant to this effect but may even show an increase in plasma beta-lipoproteins. In an attempt to find an explanation for these striking differences, we have studied the pharmacokinetics of clofibrate in FHC patients at both extremes of responsiveness. The results disclosed several major differences between the two groups. Plasma clofibric acid (CPIB) measured during the chronic administration of the drug was significantly higher in the responders than in the non-responders, whether all patients in each group or only those with tendon xanthomas were considered. Plasma CPIB concentrations were negatively correlated with body weight in the responders but not in CPIB-resistant patients. They were also inversely proportional to decreases in plasma beta-lipoprotein cholesterol after chronic clofibrate administration in the responsive group, but directly proportional to increases in the non-responders. Increasing the dose of clofibrate from 2 to 3 g/day in CPIB-resistant patients always resulted in an increase in plasma CPIB levels, but this was followed in some patients by a decrease and in others by an increase in plasma beta-lipoprotein cholesterol concentrations, so that the overall effect was not statistically significant. The half-life of plasma CPIB was measured over 48 h after a single 1-g dose of clofibrate in patients who had not received this drug for at least 3 weeks. Half-life was significantly longer in the responsive patients. In addition, the bioavailability and the rate of absorption of clofibrate tended to be higher in this group than in the resistant patients. We suspect that both groups differ not only in the metabolic handling of clofibrate but also in some aspect of their beta-lipoprotein cholesterol metabolism.

Drug distribution in renal failure.

Plasma protein binding of many drugs is impaired in patients with renal disease. This often results in a larger apparent volume of distribution and a larger clearance of the drug compared to that observed in patients with normal renal function. Hence, renal disease can also influence the pharmacokinetics of drugs that are eliminated from the body by biotransformation rather than by renal excretion, Repetitive administration of a given dose of a drug that is eliminated from the body by nonrenal mechanisms may result in considerably lower steady-state concentrations of total drug in the plasma of patients with renal disease than in that of patients with normal renal function. On the other hand, in the absence of liver disease, the average steady-state serum concentration of free (unbound) drug is likely to be the same in both groups of patients. For this reason, it is probably not necessary to change the usual daily dose of a drug that is eliminated from the body by nonrenal mechanisms when it is given to a patient with renal disease. However, such drugs should be administered in divided doses to minimize adverse effects.

9-Chloro-2,3-dihydro-5H-1,4-dioxepino(6,5-b)benzofuran, a novel antilipidemic agent structurally related to clofibrate.

The synthesis and antilipidemic activity of 9-chloro-2,3-dihydro-5H-1,4-dioxepino[6,5-b]benzofuran (3), a novel enol lactone which is considerably more resistant to serum esterase hydrolysis than clofibrate (1), are discussed. Whereas both 3 and 1 reduced hypercholesterolemic and hypertriglyceridemic serum levels in the Triton WR-1339 induced hyperlipidemic Sprague-Dawley rat to normal, the hydrolysis product of 3, namely 5-chloro-3(2'-hydroxyethoxy)-2-benzofurancarboxylic acid (4), was found to be inactive. Further, 3 is comparable to the hydrolysis product of 1 when both were assessed for their ability to block norepinephrine (NE) induced lipolysis in vitro. 4 is inactive at comparable concentrations (5 times 10(-4)-10(-3) M). The antilipidemic action of 3 and 1 may, in part, be due to their ability to block NE-induced lipolysis.

Synthesis and pharmacological evaluation of a clofibrate-related tricyclic spirolactone, 5-chloro-4',5-dihydrospiro[benzofuran-2(3H),3'(2'H)-furan]-2'-one.

The chemistry and pharmacology of the title compound, spirolactone 4, are reported. The synthesis represents a new approach to the preparation of spiro compounds. The pharmacological profiles of 4 are compared to that of clofibrate in Triton-induced hyperlipidemic, sucrose-fed, and normal Sprague-Dawley rat models. Clofibrate was effective in all animal models, but the spirolactone 4 exhibited antitriglyceridemic activity only in the Triton model. The inactivity of 4 in sucrose- and chow-fed rats could not be attributed to a resistance to hydrolysis by serum esterases. Comparative studies revealed that inhibition of hepatic HMG-CoA reductase activity may not be an index of hypocholesterolemic action in sucrose-fed rats. Additionally, only clofibrate exhibited significant changes in components of the hepatic microsomal monooxygenase system.

Drug protein binding and the nephrotic syndrome.

A reduction in plasma albumin concentration, as seen in patients with the nephrotic syndrome, is usually associated with a decrease in plasma protein binding of highly bound drugs. Therefore, the fraction of the unbound drug increases, but the absolute free concentration remains essentially unchanged due to a compensatory reduction in the steady state total plasma concentration. With phenytoin, protein binding and plasma albumin concentration are closely related, so that the degree of binding can be estimated without specific binding techniques. To be able to correctly interprete plasma levels the degree of protein binding should be known, since a reduced total concentration may be fully effective, if the free drug fraction is increased in hypoalbuminaemic patients. Although the mean steady state plasma concentration of highly bound drugs is not affected in the nephrotic syndrome, a greater fluctuation of the unbound level is observed between doses, offering a possible explanation for the increased incidence of toxicity in hypoalbuminaemic patients. As a consequence, shorter dosing intervals of these drugs seems to be advisable, rather than a reduction in the total daily dose. Reduced protein binding is accompanied by an increase in the total plasma clearance which is a function of the elimination rate constant and the volume of distribution.

Role of testosterone in the induction of hepatic peroxisome proliferation by clofibrate.

Hepatic peroxisome proliferation is induced by a number of agents, including clofibrate. Sustained proliferation of peroxisomes is associated with the development of hepatocellular carcinoma. In the present study, we have investigated the role of testosterone in peroxisome proliferation induced by clofibrate. Three groups of male rats (intact, castrated, and castrated replaced with testosterone) were studied. Proliferation of peroxisomes was induced by feeding clofibrate (0.25%, 0.50%, and 1.0% of diet) for 2 weeks. Peroxisome proliferation was monitored by measuring total peroxisomal beta-oxidation activity. In intact rats, the peroxisomal beta-oxidation activity (nmol/min/mg protein) increased in a dose-dependent manner and was 7.2 +/- 0.4, 52.6 +/- 7.5, 63.2 +/- 3.7, and 92.4 +/- 4.0 at clofibrate doses of 0%, 0.25%, 0.50%, and 1.0%, respectively. In contrast, in castrated rats, the total peroxisomal beta-oxidation activity was significantly (P < .01) lower at clofibrate levels of 0.25% and 0.50% (25.8 +/- 2.7 and 42.5 +/- 2.2, respectively), but not at the clofibrate level of 1.0% (85.0 +/- 6.3). Testosterone replacement of castrated rats restored the peroxisomal beta-oxidation activity. To determine whether the above results were related to the metabolism of clofibrate in the absence or presence of testosterone, we measured serum clofibrate levels. These levels were 50% lower in castrated rats than in intact rats or in testosterone-treated castrated rats. The activity of hepatic uridine diphosphate (UDP)-glucuronyltransferase, the enzyme catalyzing the glucuronidation of clofibrate, was measured using either bilirubin or 4-methylumbelliferone as substrates and was found to be unaffected by castration or testosterone treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of colestipol hydrochloride on the bioavailability and pharmacokinetics of clofibrate.

Since it has been reported by several authors that colestipol HCl and clofibrate have an additive effect in lowering serum cholesterol levels, it was felt advisable to evaluate the blood levels of clofibrate when given simultaneously with colestipol HCl to see whether there was any evidence for drug interaction between the two products that might dictate a need for separation of their administration time. After concomitant single-dose administration, the serum p-chlorophenoxyisobutyric acid levels, bioavailability parameters, and pharmacokinetic parameters investigated provided no evidence for an interaction and suggested that colestipol and clofibrate can be administered concomitantly or at separated in tervals according to whichever dosage regimen is deemed advisable by the physician.

A gas-liquid chromatographic determination of p-chlorophenoxyisobutyric acid and its comparison to an ultra violet method.

1. A gas-liquid chromatographic procedure for the determination of p-chlorophenoxyisobutyric acid (CPIB) has been elaborated and compared to the UV spectrophotometric procedure of Barrett and Thorp. 2. Both methods are specific when used to determine CPIB levels in normal sera from laboratory animals or humans treated with clofibrate (Atromid-S). Serum from patients treated with other drugs or abnormal sera from patients affected with a variety of diseases will often contain high and fluctuating levels of non-specific UV absorbing substances and this usually precludes the use of the UV procedure. 3. The GLC method is also applicable to the analysis of CPIB in urine samples.

A high pressure liquid chromatographic determination of p-chlorophenoxyisobutyric acid and its comparison to a GLC and an ultra violet spectrophotometric method.

A rapid and reliable method for the determination of clofibric acid in serum using high pressure liquid chromatography has been elaborated and compared to a GLC and UV spectophotometric procedure. The limit of detection of the method is 0.3 micrograms/ml.

Simultaneous determination of clofibrate and its active metabolite clofibric acid in human plasma by reversed-phase high-performance liquid chromatography with ultraviolet absorbance detection.

A reversed-phase high-performance liquid chromatographic (HPLC) using ultraviolet (UV) absorbance detection method for simultaneous determination of clofibrate (I) and its major metabolite clofibric acid (II) in human plasma has been developed to support a clinical study. I, II and internal standard (I.S., III) are isolated from human plasma by 96-well solid-phase extraction (SPE) C(18)z.ccirf;AR plate and quantified by direct injection of the SPE eluent onto the HPLC with UV detection wavelength at 230 nm. Two chromatographic methods, isocratic and step gradient, have been validated from 1.0 to 100.0 microg/ml and successfully applied to plasma sample analysis for a clinical study. The lower limit of quantitation (LLOQ) is 1.0 microg/ml for both I and II when 500 microl plasma sample is processed. Sample collection and preparation is conducted at 5 degrees C to minimize the hydrolysis of I to II in human plasma.

Simultaneous GLC determination of clofibrate and clofibric acid in human plasma.

A simultaneous assay for the detection of clofibrate and its metabolite, clofibric acid [2-(p-chlorophenoxy)-2-methylpropionic acid], is described. This GLC method is rapid and does not require a derivatization step. It is sensitive to 1-microgram/ml levels of either compound in biological samples and can be used to characterize the in vivo conversion of clofibrate ester to the free acid.