Assessment of the effect of type of dairy product and of chocolate matrix on the oral absorption of monomeric chocolate flavanols in a small animal model.

This study has examined the effects of type of dairy product (whole milk, skim milk, heavy cream) and chocolate matrix (baking, dark, dairy milk, white) on the oral absorption of the chocolate flavanols (+)-catechin and (-)-epicatechin in a small animal model. In the study, each flavanol compound, as a solution in water or a dairy product or as a chocolate dispersion in water, was administered intragastrically to male Sprague-Dawley rats in an amount equal to or equivalent to 350 mg/kg. In each instance, blood samples were collected over a 5 h period, and used to measure plasma total catechin concentrations by HPLC after enzymatic hydrolysis of flavanol conjugates. Pharmacokinetic data were evaluated using a one compartment approach. Whole milk and heavy cream, and to a much lesser extent skim milk, lowered the oral absorption of both (+)-catechin and (-)-epicatechin and altered the AUC, C(max), k(a), k(e) and t1/2 values in direct proportion to their fat, but not to their protein, content. In addition, the t(max) for solutions of (-)-epicatechin in water and skim milk occurred 2 h earlier than from solutions in whole milk and heavy cream. Similarly, dispersions of baking chocolate in water and in whole milk yielded plasma levels of monomeric catechins that were, respectively, about equal to and much lower than those from aqueous solutions of authentic flavanols. A determining role for a chocolate matrix (dark, dairy milk or white chocolate) on the oral absorption of its constitutive monomeric flavanols was suggested by the apparent variability in plasma total catechins levels that existed among them both before and after their spiking with equal amounts of exogenous (+)-catechin and (-)-epicatechin. Such a variability could reflect differences among different chocolates in terms of their physical properties, matrix components, and matrix characteristics imposed by the manufacturing process used for each type of chocolate. In all the experiments, (+)-catechin demonstrated a higher oral absorption than (-)-epicatechin.

Investigation of the micellar properties of the tocopheryl polyethylene glycol succinate surfactants TPGS 400 and TPGS 1000 by steady state fluorometry.

This study has investigated the micellar properties of the d-alpha-tocopheryl polyethylene glycol succinate esters 400 (TPGS 400) and 1000 (TPGS 1000) in terms of critical micellar concentration (CMC), apparent aggregation number (N(agg)), microviscosity and micropolarity using steady state fluorescence techniques and fluorescent probes. In addition it has compared these properties against those of a Triton-type surfactant such as Triton X-100. The CMC values for TPGS 400, TPGS 1000 and Triton X-100 were 1.51 mM, 0.02 mM and 0.19 mM, respectively. The N(agg) values for TPGS 1000 and Triton X-100 were, respectively, 10 and 63. Due to the cloudiness of its aqueous solutions, no attempt was made to evaluate the microviscosity and to obtain the N(agg) for TPGS 400. Microviscosity at the probe site for all three surfactants was high and rather similar in spite of differences among their CMC values. The ability of TPGS 400 and TPGS 1000 to provide an environment for the fluorescence quenching of micelle-solubilized pyrene appears to be associated with their hydrophobic aromatic domains. To our knowledge the present study is the first attempt at systematically studying the micellar properties of the two most widely used TPGS compounds and of comparing these properties against each other and against those of an established nonionic surfactant.

A stability-indicating proton nuclear magnetic resonance spectroscopic method for the analysis of propantheline bromide in pharmaceutical samples.

A rapid, specific and accurate proton nuclear magnetic resonance (1H NMR) spectroscopic method was developed for the simultaneous quantitative analysis of propantheline bromide and its degradation product, xanthanoic acid, in bulk materials and tablets. 1,3,5-Trinitrobenzene served as an internal standard and deuterochloroform was used as the solvent for the analytical samples. The quantities of propantheline bromide and xanthanoic acid were calculated on the basis of the integrals for signals of the methine proton of propantheline at 5.09 ppm, the methine proton of xanthanoic acid at 4.99 ppm, and the aromatic protons of the internal standard at 9.39 ppm. The accuracy of the method was established through the analysis of synthetic mixtures containing the parent compound, its degradation product and the internal standard. An excellent agreement was verified between the assay results and the quantities of the various compounds in the mixtures. The mean +/- SD recovery values for propantheline bromide and xanthanoic acid from a set of 10 synthetic mixtures were 99.6 +/- 0.8% and 98.9 +/- 1.8%, respectively. The assay of 10 lots of commercial propantheline bromide tablets by 1H NMR spectroscopy indicated drug and degradate contents in the ranges 97.1-99.8% and 0.1-0.9%, respectively. In addition, the proposed analytical method was found suitable for detecting the formation of xanthanoic acid from propantheline bromide in aqueous media in concentrations below 0.1% of that of the parent compound.

A simple method for the identification and assay of iopamidol and iothalamate meglumine in pharmaceutical samples based on proton nuclear magnetic resonance spectroscopy.

A proton nuclear magnetic resonance (PMR) spectroscopic method is described for the direct assay and identification of the triiodinated radiographic contrast agents iopamidol (nonionic type) and iothalamate meglumine (ionic type) in commercial solutions and as a bulk material. Samples were prepared by simply diluting an injectable solution with or dissolving a powdered sample in D2O. Sodium acetate was added to serve as an internal standard. Quantitations were based on the resonance signals for the protons of the CH3-CO-group at 1.58 ppm (iopamidol) or 2.25 ppm (iothalamate), CH3-N-group at 2.38 ppm (meglumine) and CH3-CO-group at 1.92 ppm (acetate). The mean +/- SD (n = sets of 10 samples each) recovery of iopamidol, iothalamic acid and meglumine from synthetic mixtures with the internal standard were 99.6 +/- 0.63, 99.7 +/- 0.66 and 99.9 +/- 1.18%, respectively; with the values ranging from 98.7-100.9% for iopamidol and iothalamate, and from 98.3-100.8% for meglumine.

Monohydroxylation and esterification as determinants of the effects of cis- and trans-9-octadecenoic acids on the permeation of hydrocortisone and 5-fluorouracil across hairless mouse skin in vitro.

The effects of cis-9-octadecenoic acid (oleic acid) and of a group of chemically related cis- (ricinoleic acid) and trans- (ricinelaidic acid) 12-monohydroxylated derivatives and their corresponding ethyl and methyl esters on the skin permeation of model hydrophobic (hydrocortisone, log K=1.61) and hydrophilic (5-fluorouracil, log K=-0.89) drugs was investigated in vitro using excised hairless mouse skin. Drug solutions were prepared in propylene glycol, with and without the addition of a fatty acid to a level of 5%. Whereas the addition of oleic acid markedly enhanced the transdermal flux of both drugs relative to a sample in propylene glycol alone (hydrocortisone approximately 1800-fold; 5-fluorouracil approximately 330-fold), that of a cis- or trans-12-monohydroxylated analog of oleic acid resulted in only a small increase (1.4-2.7-fold for hydrocortisone; 4.4-6.6-fold for 5-fluorouracil). On the other hand, the methyl and ethyl esters of cis- and trans-12-hydroxy-9-octadecenoic acid exerted a much greater enhancing effect (327-720-fold for hydrocortisone, 42-74-fold for 5-fluorouracil) than the corresponding parent fatty acids. Furthermore, whereas the ethyl esters were found to have a greater effect on the skin permeation of hydrocortisone than the methyl esters, the reverse was true with regards to 5-fluorouracil. Additionally, the esters of trans-12-hydroxy-9-octadecenoic acid promoted permeation to an extent comparable to that achieved with their cis-counterparts.

Evaluation of the effect of polyethylene glycol 400 on the nasal absorption of nicardipine and verapamil in the rat.

This study has investigated the effect of polyethylene glycol (PEG) 400 on the intranasal absorption and ensuing pharmacokinetics of the calcium entry blockers nicardipine and verapamil in a rat model. To solutions of nicardipine in acetate buffer pH 5.0 and of verapamil in distilled water, PEG 400 was added in concentrations of 0-5%. The nasal bioavailability of nicardipine from plain buffered solution was 44%, and increased steadily to 56-79% in direct proportion to the amount of PEG 400 added. Verapamil, on the other hand, exhibited an intranasal bioavailability of 52% in the absence of PEG 400, and between 61-68% in the presence of increasing concentrations of PEG 400. None of the formulations tested was found to cause adverse effects on the morphology and integrity of the nasal mucosa.

Development of a simple spectrophotometric method for propylene glycol detection in tablets.

A simple spectrophotometric procedure was developed and validated to indirectly assess the quantities of propylene glycol (PG) remaining in compressed liquid/powder admixtures. Such simplified quantitation may facilitate several testing procedures related to various aspects of formulation development and material testing of pharmaceutical powder excipients using various nonvolatile liquids as the diluents. In the present study, this new and simple approach for PG quantitation was developed as an integral part of a new method termed the liquisolid compressibility (LSC) test, used to characterize the compaction behavior of powder excipients. According to LSC testing, several admixtures of a nonvolatile liquid (in this case PG) and a powder, differing in their PG/powder weight ratio, are compressed in order to assess their compactabilities. The PG content of such compacts may then be directly quantitated by the USP gas chromatographic method or, indirectly, by this new simple spectrophotometric procedure. The new approach involves the addition of a dye marker to the PG prior to its incorporation into the powder. After compression, the PG amount remaining in the compacts may be determined by simply extracting the dye from the tablets and analyzing the extracts spectrophotometrically. In this manner, the dye content thus obtained may be extrapolated to the respective net amount of PG originally added as a dye/PG solution to the powder. Statistical comparison of the results obtained from both methods revealed almost absolute correlation.

Simplified reversed-phase HPLC method with spectrophotometric detection for the assay of verapamil in rat plasma.

A high-performance liquid chromatographic (HPLC) method was developed for the assay of verapamil in rat plasma. After deproteinization of the plasma sample with an acetonitrile-perchloric acid (8:2) mixture containing dextromethorphan, the internal standard, an aliquot of the supernatant was directly analyzed on a cyanopropylsilane column with methanol-acetonitrile-triethylamine acetate buffer (10:30:60) as the mobile phase and detection at 235 mm. At a flow rate of 1.5 ml min-1, a complete analysis was completed in less than 6 min. The method was linear for verapamil concentrations in the range 0.5-10 micrograms ml-1 (r = 0.9999). Recoveries for the same drug concentrations from spiked rat plasma ranged from 85.6-93.0% (n = 8). The mean RSD values for intraday and interday assay reproducibility (n = 3) were, in both cases, less than 0.9%. The limit of detectability was about 0.1 microgram ml-1. The method was found useful to monitor the plasma levels of verapamil in rats that had received this drug by the nasal, oral and intravenous routes of administration.

The effect of ethanol drinking on opioid analgesia and receptors in mice.

Recent studies suggest substantial interactions between opioids and ethanol (EtOH). Both in vivo and in vitro experiments indicate that EtOH can regulate opioid systems and that opioids can modify EtOH consumption. In the present studies, we examined if EtOH consumption altered opioid receptors and the potency of opioid analgesics. Mice were given unlimited access to 6-7% EtOH alone for 7 days or were allowed to drink increasing concentrations (3-6%) of EtOH over 13-14 days. Controls had access to water. The EtOH groups drank significantly less volume than controls, although there were no significant differences in body weight or baseline nociception. The analgesic (tail flick) potency of SC morphine was decreased by approximately 1.6-2.0-fold in EtOH-treated mice. A single acute dose of EtOH (1 g/kg) that produced blood alcohol levels in excess of that for 7 day exposure to EtOH, did not change morphine's analgesic ED50, suggesting that chronic exposure to EtOH was necessary for the reduction in potency. The change in morphine potency was not due to pharmacokinetic differences because EtOH consumption did not modify the concentration of morphine in brain and spinal cord. The analgesic potency of a delta-opioid receptor agonist (ICV DSLET) was also decreased by approximately 2-fold. Saturation binding studies indicated no changes in the density or affinity of brain and spinal cord delta-opioid ([3H]DPDPE, [3H]DSLET, [3H]DeltorphinII) and mu-opioid ([3H]DAMGO) receptors. Similarly, there was no significant effect of EtOH on delta-opioid receptor mRNA in either brain or spinal cord preparations. Taken together, these data suggest that EtOH consumption decreases the analgesic potency of opioids in mice through a mechanism that is unrelated to pharmacokinetics or opioid receptor changes in brain and cord.

Simple 1H NMR spectroscopic method for assay of salts of the contrast agent diatrizoate in commercial solutions.

A simple, accurate, and specific 1H NMR spectroscopic method was developed for the assay of diatrizoate meglumine or the combination diatrizoate meglumine and diatrizoate sodium in commercial solutions for injection. A mixture of injectable solution and sodium acetate, the internal standard, was diluted with D2O and the 1H NMR spectrum of the solution was obtained. Two approaches were used to calculate the drug content, based on the integral values for the -N-CO-CH3 protons of diatrizoic acid at 2.23 ppm, and -N-CH3 protons of meglumine at 2.73 ppm, and the CH3-CO-protons of sodium acetate at 1.9 ppm. Recoveries (mean +/- standard deviation) of diatrizoic acid and meglumine from 10 synthetic mixtures of various amounts of these compounds with a fixed amount of internal standard were 100.3 +/- 0.55% and 100.1 +/- 0.98%, respectively. In addition to providing a direct means of simultaneously assaying diatrizoic acid and meglumine, the proposed NMR method can also be used to identify diatrizoate meglumine and each of its molecular components.

Determination of the optical purity of timolol maleate by proton nuclear magnetic resonance spectroscopy with a chiral Pr(III) shift reagent.

A 1H NMR spectroscopic method with chiral shift chelate is presented for the determination of the optical purity of timolol maleate. Optimum experimental conditions were established by studying the interactions of solvents (CCl4, CDCl3), substrate concentration, and the type and concentration of chiral lanthanide chelate (Pr(hfc)3, Eu(hfc)3). Larger induced shift (delta delta) and enantiomeric shift difference (delta delta delta) values, and more detailed spectral differences were obtained with Pr(hfc)3 than with Eu(hfc)3. By monitoring the spectral changes of the resonance signals for the enantiomeric -C(CH3)3 protons, suitable conditions for quantitative determinations were found when 0.1 molar equivalents of Pr(hfc)3 were complexed with 0.074 M of substrate. Enantiomeric compositions were calculated from the relative intensities of the enantiomeric -C(CH3)3 proton resonances. Based on the analysis of six synthetic enantiomeric mixtures, the mean +/- SD recovery of (R)-(+)-timolol by the proposed method was 99.5 +/- 1.17% of the amount added.

Proton nuclear magnetic resonance spectroscopic detection and determination of ethylene glycol dimethacrylate as a contaminant of methyl methacrylate raw material.

A simple, specific, and accurate proton nuclear magnetic resonance (1H NMR) spectroscopic method is presented for detection and assay of ethylene glycol dimethacrylate dimer as a contaminant of methyl methacrylate monomer. In addition to minimizing exposure of the analyst to the irritant and toxic methacrylic acid esters, the proposed method requires no sample preparation. Quantitations are based on integrals for signals of methylene protons of ethylene glycol dimethacrylate at 4.37 ppm and methyl protons of methyl methacrylate at 3.70 ppm. Analysis of 10 synthetic mixtures of the monomer with 1-11% of dimer yielded a dimer recovery of 100.5 +/- 2.05% (mean +/- standard deviation). Correspondence (correlation coefficient, r = 0.9999) between the amount of dimer added and the amount found was excellent. The proposed method measures as little as 1% of dimer.

Nasal Delivery of Atenolol and Timolol in the Rat and the Effect of Absorption Enhancers.

This study has investigated the nasal mucosa as an alternative site for the administration of atenolol and timolol maleate, two antihypertensive agents whose oral administration is subject to either incomplete absorption (atenolol) or significant first-pass effect (timolol). To this end, the intranasal absorption of these drugs was first evaluated in an in vivo rat model, with and without the absorption enhancers amastatin and sodium glycocholate, and next compared with those obtained after oral and intravenous dosings. Use of the intranasal route resulted in higher plasma drug levels than by the oral route (p < 0.05) and in systemic bioavailabilities that compared very favorably with those obtained intravenously (ca. 90% for both drugs). Bioavailability of the title drugs from the nasal mucosa improved upon coadministration with an absorption enhancer (96-98%, atenolol; ca. 99%, timolol).

Determination of the optical purity and absolute configuration of threo-methylphenidate by proton nuclear magnetic resonance spectroscopy with chiral solvating agent.

The direct determination of both the optical purity and absolute configuration of threo-methylphenidate has been accomplished in a simple, specific, and accurate manner by 1H-NMR spectroscopy. The enantiomeric resonances of threo-methylphenidate were effectively resolved in CDCl3 solution by the addition of the chiral solvating agents (R)-(-)- or (S)-(+)-2,2,2,-trifluoro-1-(9-anthryl)ethanol. Optical purities were determined on the basis of the intensities of the enantiomeric ester methyl proton resonances; the assignment of enantiomeric configurations was based on the relative field positions of these resonances and the examination of molecular models. The analysis of synthetic enantiomeric mixtures of threo-methylphenidate by the proposed NMR method resulted in assay values that agreed closely with the known quantities of each enantiomer in the mixtures tested. The mean +/- SD recovery value for the (2S,2'S)-(-)-threo-enantiomer, amounting to 99.9 +/- 0.6% of added (n = 10), correlated well with that previously found by 1H-NMR spectroscopy with a chiral Eu(III) shift reagent. However, the present approach is simpler, shows less reliance on reagents and solvents of a high purity, and does not require strict anaerobic working conditions.

Stability-indicating proton nuclear magnetic resonance spectroscopic assay method for furosemide in tablets and injections.

A simple, specific, and accurate proton nuclear magnetic resonance (1H-NMR) spectroscopic method has been developed for the identification and assay of furosemide and its degradation product, 4-chloro-5-sulfamoylanthranilic acid (CSA), in tablets and injections. Dissolution of the sample in D2O-NaOD resulted in a solution yielding the required separation among the resonance signals of furosemide, CSA, and tert-butyl alcohol, the internal standard. The mean +/- SD recovery values of furosemide and CSA from 10 synthetic formulations were 99.6 +/- 0.8 and 98.9 +/- 1.7%, respectively. Commercial tablets (6 lots) and injections (5 lots) of furosemide were assayed by the proposed method and found to contain 53.1-99.8% furosemide and 0.3-45.2% CSA.