Nanomatrix Coated Stent Enhances Endothelialization but Reduces Platelet, Smooth Muscle Cell, and Monocyte Adhesion under Physiologic Conditions.

Cardiovascular disease is presently the number one cause of death worldwide. Current stents used to treat cardiovascular disease have a litany of unacceptable shortcomings: adverse clinical events including restenosis, neointimal hyperplasia, thrombosis, inflammation, and poor re-endothelialization. We have developed a biocompatible, multifunctional, peptide amphiphile-based nanomatrix coating for stents. In this study, we evaluated the ability of the nanomatrix coated stent to simultaneously address the issues facing current stents under physiological flow conditions in vitro. We found that the nanomatrix coated stent could increase endothelial cell migration, adhesion, and proliferation (potential for re-endothelialization), discourage smooth muscle cell migration and adhesion (potential to reduce neointimal hyperplasia and restenosis), and decrease both platelet activation and adhesion (potential to prevent thrombosis) as well as monocyte adhesion (potential to attenuate inflammatory responses) under physiological flow conditions in vitro. These promising results demonstrate the potential clinical utility of this nanomatrix stent coating, and highlight the importance of biocompatibility, multifunctionality, and bioactivity in cardiovascular device design.

Controlled-release matrix tablets of ibuprofen using cellulose ethers and carrageenans: effect of formulation factors on dissolution rates.

The study was conducted to investigate the effects of carrageenans, and cellulose ethers on the drug release rates of ibuprofen controlled-release tablet matrices prepared by direct compression. Polymer blends containing carrageenans or cellulose ethers were used for the formulation and the effect of varying the polymer concentration on the release of the drug was studied. Other factors such as changes in surface topography of the matrices due to hydration were observed using a cryogenic scanning electron microscopy technique. Multiple regression analysis was used to predict the time for 50% release (t50) as a function of the concentration of the polymers used. Most of the formulations showed linear release profiles (r(2)>or=0.96-0.99) and sustained the release of ibuprofen over 12-16 h. The highest t50 (9.3 h) was for the formulation that contained a blend of 1:2 ratio of Viscarin and HPMC, while the lowest (3 h) was for the matrices that contained a 2:1 ratio of methylcellulose and Gelcarin. The majority of the matrix tablets that contained 10% polymer disintegrated prematurely. Of all the polymer blends that were investigated, the combination of Viscarin and HPMC gave almost linear release profiles over the entire range of concentration that was studied. The least effective combination was methylcellulose in combination with HPMC. Most of the formulations released ibuprofen by an anomalous (non-Fickian) transport mechanism, except those matrices that contained methylcellulose and Gelcarin (in a 1:1 and 1:2 ratio), which showed zero-order release.

Plasma levels of clobazam after three oral dosage forms in health subjects.

As can be seen from the tables, the terminal half-life of clobazam is about 50 hours, and from a solid dosage form the peak plasma level occurs approximately 1.5 hours after ingestion. Thus, there is a significant, yet relatively short, dosage form delay effect when the solid dosage forms are compared to the rapidly available solution of the drug. However, based on the areas under the curve, comparison of the solid dosage forms with the solution indicates that the fraction of clobazam absorbed is 1. Pupil diameter measurement at 2, 4, and 6 hours after ingestion of clobazam correlated well with the plasma levels at these times. Pupils were constricted to the highest degree at 2 hours and approached the initial pupillary diameter at the 6-hour measurement.

Plasma level studies of penbutolol after oral dose in man.

Plasma levels of penbutolol (HOE 893d) were determined in eight healthy adult male subjects after oral administration of 50-mg capsules. Fast absorpiton of the drug from the gastrointestinal tract was indicated by the rapid increase in plasma levels during the absorption phase, with a peak time at about 1 hour after dosing in all subjects. After the peak level, plasma concentrations declined biexponentially, with an average half-life of 2.5 and 27 hours for the fast and slow disposition phases, respectively. These values were in good agreement with data previously found for this drug. Cumulative excretion of intact drug in the urine of the eight subjects during 72 hours after dosing was less than 4 per cent, except for one subject who excreted 9.82 per cent of the dose. Large individual variations were found for area under the plasma level curves, disposition rates, and amounts of intact drug excreted in the urine. Significant pharmacologic effects were noted in all eight subjects at the 50-mg dose level, and mild side effects were evident in one half of these subjects. The average drop in blood pressure and pulse rate for all subjects was 26/18 mm Hg and 19 beats per minute, respectively.

Pharmacokinetic studies of pentylenetetrazol in dogs.

Pharmacokinetic profiles of pentylenetetrazol in the dog were studied following rapid intravenous and oral administrations of a convulsant dose (15-20 mg/kg). Plasma level-time curves after a rapid intravenous injection showed biexponential decline, indicating that the disposition of this drug in the dog follows a two-compartment body model. Pharmacokinetic parameters were calculated from the intravenous data. After oral administration of the solution dose, the peak plasma level appeared at about 30 min postdose, indicating that the absorption occurs rapidly. Areas under the oral plasma level-time curves s howed that the drug was absorbed completely and that the first-pass metabolism effect was minimal. The ligation studies of the kidney and the liver suggested that the main elimination pathway of this drug was biotransformation in the liver. The average plasma half-life was 1.4 hr. At steady state, the volume of distribution was approximately equivalent to the volume of the total body water.

Kinetics of hydrolysis of methenamine.

The kinetics of degradation of methenamine were studied in citrate--phosphate buffers between pH 2.0 and 7.4 at 37.5 degrees. GLC was used to monitor the rate of hydrolysis. The conversion of methenamine to formaldehyde was found to be pH dependent in the buffers of constant ionic strength, with the reaction half-life decreasing from 13.8 hr at pH 5.8 to 1.6 hr at pH 2.0. The kinetics of degradation also were measured at 47, 57, and 67 degrees, and the reaction obeyed the Arrhenius relationship. At pH 2.0, the activation energy was calculated to be 23.5 kcal/mole; at pH 5.1, it was 12.0 kcal/mole.

Distribution of tetracycline in red blood cells.

The distribution of tetracycline into human red blood cells was studied in vitro at 37 degrees. The drug was taken up rapidly by the cells, and its distribution equilibrium was reached after approximately 10 min of incubation. The steady-state distribution ratio of the drug between the red cells and extracellular fluid of 0.9% NaCl solution was 2.84, while the distribution ratio between the cells and the plasma solution was 0.9. The reduced cellular uptake in plasma was due to binding of the drug to plasma components. Calcium ions in plasma appeared to reduce tetracycline uptake by the red cells. The red cell distribution of tetracycline in dogs was in close agreement with the in vitro data using the washed human red cells. A dog suffering from severe hypoalbuminemia showed greater uptake of the drug by the erythrocytes, while a normal healthy dog exhibited the red cell-plasma distribution ratio of 0.98. The release rate of tetracycline from the preloaded cells into normal saline solution indicated that the release was directly proportional to the cellular concentration of the drug; the first-order release rate was approximately 1.38 hr-1.

GLC determination of methenamine in tablets.

A rapid and sensitive GLC method was developed for the quantitative determination of methenamine in tablets. The method was shown to possess several advantages over the official NF assay. After dissolution of the whole tablet in absolute ethanol and addition of an internal standard (pentylenetetrazol), an aliquot was injected into the gas chromatograph for analysis. The sample was chromatographed using a stainless steel column packed with 10% OV-17 on Chromosorb W-HP. Quantitation was achieved by measuring peak heights. The simplicity, directness, extreme rapidity, and accuracy of the method represents an improvement over the official method and the other proposed assays.

Anti-inflammatory activity of ketoprofen gel on carrageenan-induced paw edema in rats.

The anti-inflammatory activity of a 1% ketoprofen gel containing 20% Pluronic F-127 was evaluated using the carrageenan-induced rat paw edema method. The activity of the gel was compared with that of other topical nonsteroidal anti-inflammatory drug (NSAID) preparations. The Pluronic gel formulation was significantly more effective against edema formation than other ketoprofen gels used. The 1% ketoprofen gel in the Pluronic base inhibited 53% of the carrageenan-induced edema formation as compared with 38% inhibition obtained with a 3% ketoprofen gel in a Carbopol-based formulation. The topical ED50 of the 1% ketoprofen gel was 2.2 mg/kg whereas the oral ED50 of ketoprofen in a suspension was 6.1 mg/kg, indicating that the relative equiponderal availability of the topical gel was nearly three times that of the oral suspension. The application of 50 mg of the 1% ketoprofen gel on the rat hind paw at various time intervals from 0 to 24 h prior to the carrageenan injection significantly inhibited edema formation in all groups of dosed rats. A significant correlation was found between the percent inhibition of rat paw edema and the log dose of ketoprofen injected subplantarly for the dose range between 0.1 and 10 micrograms/paw.

Separation and quantitation of methenamine in urine by ion-pair extraction.

An ion-pair extraction technique is described for separating methenamine, a urinary tract antibacterial agent, from formaldehyde in human urine samples. Separation conditions are developed from extraction constants for the methenamine-bromocresol green ion-pair. The technique involves adsorption of the ion-pair onto a silica cartridge and elution with methylene chloride:1-pentanol (95:5). Methenamine is freed from the ion-pair by the addition of excess tetrabutylammonium iodide and converted to formaldehyde (determined spectrophotometrically) by reaction with ammonia and acetylacetone. Linear standard plots were obtained from urine containing methenamine which was diluted to 10-160 micrograms/mL. The lower limit of detection was 6 micrograms/mL of methenamine. Absolute recovery from urine was greater than or equal to 94.5%. The precision (CV) of detection of methenamine in the presence of formaldehyde was less than 2%, and less than or equal to 4.5% for the detection of formaldehyde in the presence of methenamine. No interferences were noted. The applicability of the method was demonstrated by analysis of human urine levels of both methenamine and formaldehyde following oral administration of a methenamine salt to a volunteer.

Release rates of ketoprofen from poloxamer gels in a membraneless diffusion cell.

Release rates of ketoprofen from topical gels consisting of poloxamer 407 were evaluated using a membraneless diffusion cell with isopropyl myristate as the receptor medium. The effects of formulation variables such as polymer content (20-30%), drug (0.2-3.0%) and ethanol (0-20%) concentrations, pH (3.0-6.0), and temperature of the gels (25-45 degrees C) on drug release were studied. Release of ketoprofen from the gel decreased exponentially as the polymer concentration increased. Over the temperature range studied, the drug release rate appeared to correlate with the Arrhenius function. The change of the gel pH from 3 to 6 substantially increased the release rate of ketoprofen. The enhanced drug release in the presence of ethanol is attributed to the decrease in viscosity of the gel. With higher drug loading in the gel, an increase in the release rate, but a reduction of diffusion coefficient of the drug, was observed.

Interaction of tricyclic antipsychotic and antidepressant drugs with 1-anilino-8-naphthalenesulfonic acid.

The binding of 1-anilino-8-naphthalenesulfonic acid to selected tricyclic antipsychotic and antidepressant drugs was studied by fluorescence spectroscopy. The acid exhibited an increase in fluorescence intensity accompanied by a hypsochromic shift of the emission lambdamax in the presence of these drugs. These fluorescence characteristics, in addition to those of acid-drug complexes after addition of potassium chloride or urea, suggested that binding was hydrophobic. The spectra also provided evidence regarding the importance of certain structural features of drugs in determining the nature of binding.

Pharmacokinetics of insect repellent N,N-diethyl-m-toluamide in beagle dogs following intravenous and topical routes of administration.

The common topical insect repellent N,N-diethyl-m-toluamide (DEET) has caused serious adverse effects in the users of DEET products due to its high skin permeability. This study investigated the pharmacokinetics of DEET following i.v. and dermal routes of administration in beagle dogs. The pharmacokinetics of DEET was linear over the dose range of 2.5-6.0 mg/kg. Following the i.v. dosing, plasma DEET concentrations declined biexponentially with an elimination half-life of 2.56 h. Volume of distribution at steady-state, systematic clearance, and mean residence time were estimated as 6.21 L/kg, 2.66 L/h/kg, and 2.34 h, respectively, indicating that DEET underwent extensive extravascular distribution and rapid elimination. After the dermal application of a commercial lotion and a new DEET lotion at 15 mg of DEET/kg, plasma DEET concentrations peaked at 1-2 h postdose. The DEET transdermal bioavailability and mean absorption time were 18.3% and 2.05 h, respectively, for the commercial lotion and 14.0% and 2.66 h, respectively, for the new lotion. The difference in DEET transdermal absorption between the two lotions suggested that commercial DEET products could be optimized for reduced DEET absorption for safer use.

Formation of a cyclic derivative of ethacrynic acid with diazomethane.

Samples of ethacrynic acid were treated with methanol-hydrochloric acid or with diazomethane. GLC and mass spectrometric analysis indicated that the methanol-hydrochloric acid reaction gave the expected methyl ester, whereas diazomethane treatment gave a compound containing an additional 14 mass units. Accurate mass measurement and PMR and IR spectra showed that this product was a cyclic derivative of the methyl ester of ethacrynic acid, methyl 4-(2,3-dihydro-4-ethyl-5-furyl)-2,3-dichlorophenoxyacetate. Either derivatization method can be used for development of an assay for ethacrynic acid.

Nitrofurantoin solubility in aqueous urea and creatinine solutions.

Experiments were carried out to determine the effect of urea and creatinine on the solubility of nitrofurantoin in water at different temperature and pH conditions. The addition of urea to aqueous media increased nitrofurantoin solubility up to a maximum concentration level and then decreased solubility at higher urea concentrations. The amount of urea needed to bring about maximum nitrofurantoin solubility was dependent on temperature and ranged between 1.75 and 2.50%. Spectral studies suggest a possible interaction between urea and nitrofurantoin molecules. Nitrofurantoin solubility increased with an increasing creatinine concentration ranging from 0.05 to 1.6%. Spectral studies indicate a strong interaction between creatinine and nitrofurantoin molecules in solution. The combined effect of urea and creatinine of the solubility of nitrofurantoin could account for the absence of crystalluria with this drug, even though unusually high concentrations in urine have been reported.

Drug-biomolecule interactions: fluorescence studies on interaction of aminonaphthalenesulfonic acid derivatives with serum albumins.

The binding of the three aminonaphthalenesulfonic acid derivatives to human and bovine serum albumins was studied by measuring the fluorescence enhancement of the compounds. The number of binding sites of human and bovine serum albumins for these compounds appears to be one and two, respectively, under the experimental conditions. As the molar ratio of the fluorescent compounds to bovine serum albumin increased, the binding sites appeared to increase for the compounds. The quenching of the native fluorescence of albumin was examined by the successive addition of methanolic solutions of these compounds. 1-Anilinonaphthalene-8-sulfonate quenched the protein fluorescence to a greater extent than the other compounds studied, indicating that 1-anilinonaphthalene-8-sulfonate molecules are bound more closely to the tryptophan residues of albumin. The finding that the three compounds did not quench the fluorescence of tryptophan dissolved in water indicates no direct molecular interaction between tryptophan and the three fluorescent probes. The driving force for binding may be due to the structural characteristics of the amino acid sequence surrounding the tryptophan residues.

Blood level studies of all-trans- and 13-cis-retinoic acids in rats using different formulations.

Studies to determine the bioavailability of all-trans-retinoic acid from a microencapsulated product were carried out using rats as test animals. The microcapsules were tableted in rat food and individual rats given a tablet containing the equivalent of 10 mg of all-trans-retinoic acid. Comparisons were made with bioavailability data obtained after intravenous and oral administrations of a solution and a suspension. The elimination of all-trans-retinoic acid following intravenous administration of 1- to 5-mg doses occurred by dose-dependent kinetics. The half-lives for the terminal linear portion of the elimination phase after the plateau level were 0.78, 0.74, and 0.93 hr for the 1-, 2.5-, and 5-mg doses, respectively. Based on the doses administered and the relative area under the serum level curves, the all-trans-retinoic acid microcapsules were found to be approximately 34% as bioavailable as the solution dosage form and the microfine suspension 93% as bioavailable. The bioavailability of all-trans-retinoic acid in oral solution was approximately 40% of the intravenous dose. For comparison, rats were also dosed intravenously with 13-cis-retinoic acid, and this compound was found not to follow dose-dependent kinetics at similar dosage levels used for all-trans-retinoic acid.

Improved and rapid high-performance liquid chromatographic assay for 13-cis-retinoic acid or all-trans-retinoic acid.

A rapid, specific, and sensitive reversed-phase high-performance liquid chromatographic (HPLC) assay for the quantitative determination of all-trans-retinoic acid (I) or 13-cis-retinoic acid (II) in rat serum without extraction of lyophilization is described. Chromatographic separation from retinol, serum components, and retinol acetate standard was achieved on octadecylsilane-coated particles with acetonitrile-1% ammonium acetate as th eluent. Serum samples (100 microliter) containing as little as 10 ng of retinoid were analyzed. Serum level profiles of rats dosed with the retinoids demonstrated the utility of the assay and indicated elimination half-lives of 0.58 and 0.92 hr for I and II, respectively.

Quantitative GLC determination of pentylenetetrazol in biological fluids.

A quantitative, sensitive, and specific GLC method was developed for the determination of pentylenetetrazol in water, plasma, and urine. The assay involves a single extraction of the sample into chloroform followed by centrifugation, evaporation, and chromatography. The method for pentylenetetrazol is reproducible, and the sensitivity limit of the assay is 0.5 mug of pentylenetetrazol/ml of biological fluid using a 2-ml sample. This method has a sensitivty sufficient to detect human plasma levels after therapeutic clinical doses and was successfully applied to monitor complete plasma level profiles of this drug in dogs. The data indicate that this drug is very rapidly absorbed following an oral dose, and the half-life of the drug in plasma is approximately 1 hr.

Examination of blood clobazam levels and several pupillary measures in humans.

The State-Trait Anxiety Inventory was administered to 15 subjects before initiation of the experiment. Three subgroups of five subjects were defined by computing the unweighted sum of the state and trait anxiety scores. A 40-mg dose of clobazam, a 1.5-benzodiazepine, was administered to each subject and repeated with two additional dosage forms following a 2-week washout period. Blood samples were withdrawn, and blood levels were determined by fluorometric analysis. Additionally, pupillary measures of critical flicker fusion, constriction, and dilation in response to a cognitive task were obtained at 0, 2, 4, and 6 hr. A repeated measures analysis of variance revealed that blood levels were, as expected, statistically different over time and dosage form. The pupillary constriction mirrored the blood levels in statistical patterns. The pupillary measure of cognition related to the anxiety state after the performance effects of the cognitive task were statistically removed. The results suggest that clobazam has less immediate human effect than does diazepam.