Polarographic behaviour of meloxicam and its determination in tablet preparations and spiked plasma

Meloxicam is a new non-steroidal anti-inflammatory drug (NSAID), which has a higher activity cyclooxygenase-2 (COX-2) than against cyclooxygenase-1 (COX-1), with potentially high anti-inflammatory and analgesic action. The voltammetric behaviour of meloxicam was studied using direct current (DC), differential pulse polarography (DPP) and cyclic voltammetry (CV). The influence of several variables (including nature of the buffer, pH, concentration, modulation amplitude, scan rate, drop size, etc.) was examined in DPP method for meloxicam. The best DPP response was obtained in acetate buffer pH 4.88. The peak currents were measured with a static mercury drop electrode at -1.49 V versus Ag/AgCl. Calibration curve for meloxicam was linear at a concentration range from 0.38 to 15.0 microg ml(-1). The method was validated and applied to the determination of meloxicam in tablets, which were in two different dosage forms. A spectrophotometric method reported in the literature was utilized as a comparison method. There were no significant differences between the results obtained by two methods. DPP method is also available and applicable for the determination of mentioned substance in plasma. Mean recovery was 99.20+/-0.37%. It was concluded that the developed method was accurate, sensitive, precise, reproducible and useful for the quality control of meloxicam in pharmaceuticals and spiked plasma.     

Difference spectrophotometric assay of 1,2-diphenolic drugs in pharmaceutical formulations - I. Boric acid reagent

A new procedure is described for the selective determination of drugs containing a 1,2-diphenolic moiety. The assay is based upon the measurement of difference absorbance between two equimolar solutions of the drug in pH 7 phosphate buffer, one of which also contains 0.1 M boric acid. The difference absorbance, which is maximum at about 292 nm, is due to the different spectral characteristics of the boric acid ester of the drug and of the unesterified drug and is proportional to the concentration of the drug. The accuracy, precision, sensitivity and specificity of the procedure are discussed. Applications of the assay are described for adrenaline, isoetharine, isoprenaline, levodopa and methyldopa in pharmaceutical formulations.     

A comparison of plasma levels of L(+) pseudoephedrine following different formulations,and their relation to cardiovascular and subjective effects in man

Summary Plasma concentrations of L(+)pseudoephedrine administered in clinically used dosages were determined by gas liquid chromatography using a nitrogen sensitive detector. They were measured after administration of an immediate release formulation (Sudafed) given in either a single dose of 180 mg, or three divided doses of 60 mg, and also after administration of two different sustained release preparations containing 180 mg. Ten subjects each received five treatment regimes, administration being ordered in a balanced design based on 2 five sided Latin squares. Significant differences were found between plasma concentrations and rates of urinary excretion of L(+)pseudoephedrine following administration of the different preparations. Peak plasma concentrations were greatest after 180 mg of the immediate release preparation while more sustained elevations of concentration followed administration of both sustained release preparations and the immediate release preparation in repeated doses. Despite these differences in plasma concentration significant differences in heart rate, blood pressure, or subjective ratings of mental state rarely occured, and the reasons for this are discussed. In a second study, one of the sustained release preparations was administered to 10 subjects at a dose of 180 mg twice daily for two weeks, and plasma concentrations and effects were measured. L(+)pseudoephedrine plasma levels reached a plateau in 3 days producing increased heart rate initially insomnia occurred but this disappeared after 3 days.     

Genetic toxicity assessment: employing the best science for human safety evaluation. Part II: Performances of the in vitro micronucleus test compared to the mouse lymphoma assay and the in vitro chromosome aberration assay.

The in vitro micronucleus test is commonly used in the early stages of pharmaceutical development as a predictive tool for the regulatory mouse lymphoma assay or in vitro chromosome aberration test. The accumulated data from this assay leads to the suggestion that it could be used as an alternative to the chromosome aberration test or the mouse lymphoma assay in the regulatory genotoxicity battery. In this paper, we present the results of the in vitro micronucleus test on L5178Y mouse lymphoma cells with 25 compounds from Servier research and have compared these results to those obtained in the genotoxicity regulatory battery. All the negative compounds were also negative in the in vitro micronucleus assay. Among the 14 positive compounds, two of them, positive in the mouse lymphoma assay, were found negative in the in vitro micronucleus test. However, this apparent discordance was likely to be due to cytotoxicity- or high concentration-related false positive responses in the mouse lymphoma assay. In addition, we confirmed that the in vitro micronucleus assay is useful for detecting aneugens, especially, when cells in metaphasis and multinucleated cells are also scored and when cells are allowed to recover after the long treatment. On this series of compounds, the in vitro micronucleus assay showed high sensitivity and possibly a better specificity than the mouse lymphoma assay. Thus, the in vitro micronucleus assay was shown to be at least as adequate as the mouse lymphoma assay or the in vitro chromosome aberration test to be used in the standard genotoxicity battery.     

Development of a standardized analysis strategy for basic drugs, using ion-pair extraction and high-performance liquid chromatography - II. Selection of preferred HPLC-systems

A test set of 100 basic drugs has been chromatographed on 16 preselected HPLC-systems using four different types of stationary phase (Si-, NH₂-, CN- and C₁₈-). A numerical treatment of the chromatographic data, based on the discriminating power concept, results in the selection of two preferred HPLC systems for basic drugs. both using the CN-bonded phase. The preferred eluents are n-heptane—dichloromethane—acetonitrile—propylamine (25:50:25:0.1) and acetonitrile—water—propylamine (90:10: 0.01). The two preferred HPLC systems are adopted in a standardized analysis strategy.     

Proliferative effects of estradiol, progesterone, and two CB congeners and their metabolites on gray seal (Halichoerus grypus) uterine myocytes in vitro.

Gray seal females living in the Baltic Sea have been found to exhibit a high prevalence of uterine leiomyomas. These animals are also known to accumulate lipid-soluble PCBs in their blubber. PCBs have documented endocrine-disrupting effects; to investigate whether the PCBs could be part of the genesis of uterine smooth muscle tumors in this species, gray seal myometrial cell cultures were exposed to two CBs and their metabolites, as well as to estradiol and progesterone, after which the effects were analyzed in terms of proliferative activity by measurements of BrdU absorbance and protein content. Progesterone was found to have an inhibitory effect, whereas one CB acted as a stimulant on the myometrial cell proliferation. One of the CB metabolites also seemed to have an inhibitory effect, although this could not be statistically verified. These results suggest that some CBs have effects on uterine myometrial cell proliferation in gray seals and, thus, may also take part in the growth regulation of uterine leiomyomas.     

Studies on the biliary excretion mechanisms of drugs. II. Biliary excretion of thiamphenicol, chloramphenicol and their glucuronides in the rat

Thiamphenicol (TP) or chloramphenicol (CP) administered intravenously (14 μmoles) to rats with ligated renal pedicles is rapidly excreted in bile mostly as the glucuronide (about 23 and 75 per cent in 7 hr respectively). Increasing the dose of either drug does not result in an increased excretion of glucuronide, indicating that the excretion process is saturable. TP glucuronide (TPG) or CP glucuronide (CPG) administered intravenously to rats with ligated renal pedicles is rapidly excreted into bile in high concentration as unchanged glucuronide. The maximal excretion rate of TPG or CPG (about 14.0 and 18.0 gmmoles/10 min respectively) when each glucuronide (100 μmoles) was administered is much higher than that (about 5.1 and 8.5 gmmoles/10 min respectively) when each aglycone (200 μmoles) was administered. The results suggest that the transport maxima (Tms) for the biliary excretion of TP and CP are due to a saturation of the conjugating process. CPG used in this study is isolated by a new method.     

Evaluation of the 20-day pubertal female assay in Sprague-Dawley rats treated with DES, tamoxifen, testosterone, and flutamide.

The Endocrine Disrupter Screening and Testing Advisory Committee (EDSTAC) has recommended the rodent pubertal female assay as a Tier I test to detect potential endocrine disrupters (EDs). This assay is designed to screen estrogenic activity in immature rats exposed to chemicals during sexual maturation. The aim of this study was to evaluate whether this assay can detect the EDs with effects brought about through various mechanisms. Immature Sprague-Dawley female rats (21 days of age) were dosed daily for 20 days by oral gavage (DES, tamoxifen, and flutamide) or sc injection (testosterone). The mean age at vaginal opening (VO) was 32.3 +/- 0.5 days in control rats. Although VO was unaffected by DES at doses of 0.2 and 1.0 microg/kg, a high dose of DES (5.0 microg/kg) significantly advanced the age at VO to 24 days. Both tamoxifen (50 and 200 microg/kg) and flutamide (25 mg/kg) also significantly accelerated VO to 27.8 +/- 0.5, 25.1 +/- 0.1, and 26.1 +/- 0.1, respectively. However, testosterone dose-dependently delayed VO (exposure to 1.0 mg/kg extended VO to 37.3 +/- 0.8 days, and VO did not occur in 2 of 10 animals by the time of necropsy at 41 days of age). Estrous cyclicity was monitored in rats from VO to necropsy. Irregular cycles were observed in the groups treated with DES (5.0 microg/kg), tamoxifen (200 microg/kg), testosterone (1.0 mg/kg), and flutamide (25 mg/kg). High dose of DES showed a persistent estrus state throughout the entire observation period. In addition, the number of days in diestrus was increased by tamoxifen (200 microg/kg) and flutamide (25 mg/kg) treatments. Significant decreases in ovarian weight were observed in 5.0 microg/kg DES (64% of control), 25 mg/kg flutamide (76% of control), and 200 microg/kg tamoxifen (47% of control). Testosterone also significantly decreased the ovarian weights in all treatment groups. Uterine weights were also decreased significantly at high doses of tamoxifen (200 microg/kg, 39% of control) or testosterone (1.0 mg/kg, 47% of control). In hormone analysis, tamoxifen significantly increased serum E(2) levels at 50 microg/kg. The mean serum levels of TSH were significantly increased in tamoxifen (10 and 50 microg/kg), testosterone (0.2 mg/kg), and flutamide (1.0 and 25 mg/kg) treatment groups compared with the control. However, serum T(4) levels were significantly reduced by testosterone. Furthermore, serum T(3) levels were significantly increased in DES, tamoxifen (10 and 50 microg/kg), testosterone (1.0 mg/kg), and flutamide (1.0 and 5 mg/kg). Our data demonstrate that the rodent pubertal female assay is useful for identifying potential EDs having not only estrogenic/antiestrogenic but also androgenic/antiandrogenic activities. However, further validation study is necessary to identify chemicals that operate through other action mechanisms, including steroid biosynthesis inhibitors and thyroid inhibitors. Moreover, additional data on other compounds with weak endocrine disrupting activity will be required to further characterize the sensitivity of the female pubertal assay.     

Development of a standardized analysis strategy for basic drugs, using ion-pair extraction and high-performance liquid chromatography - III. Analysis of pharmaceutical dosage forms

The usefulness of the standardized analysis strategy previously described for the determination of basic drugs in pharmaceutical dosage forms is evaluated. Several examples which typify experience in applying the strategy are reported. Ion-pair extraction techniques are compared with each other and with a classical extraction method in terms of their efficiency. The extraction technique with di(2-ethylhexyl)-phosphoric acid (HDEHP) is found to be the method of choice. The use of an internal standard is recommended. The selection of a suitable compound is greatly facilitated by referring to the chromatographic properties. It is shown that it is not necessary for the analyte and internal standard to be structurally similar. The combination of the HDEHP extraction technique with the preferred HPLC systems has been shown to be very useful in the routine analysis of pharmaceutical dosage forms.