Spectrophotometric, Difference Spectroscopic, and High-Performance Liquid Chromatographic Methods for the Determination of Cefixime in Pharmaceutical Formulations

Three simple and sensitive spectrophotometric, difference spectroscopic, and liquid chromatographic (LC) methods are described for the determination of cefixime. The first method is based on the oxidative coupling reaction of cefixime with 3-methyl-2-benzothiazolinon hydrazone HCl in presence of ferric chloride. The absorbance of reaction product was measured at the maximum absorbance wavelength (max), 630 nm. The difference spectroscopic method is based on the measurement of absorbance of cefixime at the absorbance maximum, 268 nm, and minimum, 237 nm. The measured value was the amplitude of maxima and minima between 2 equimolar solutions of the analyte in different chemical forms, which exhibited different spectral characteristics. The conditions were optimized, and Beer's law was obeyed for cefixime at 1 to 16 μg/mL and 10 to 50 μg/mL, respectively. The third method, high-performance LC, was developed for the determination of cefixime using 50 mM potassium dihydrogen phosphate (pH 3.0)methanol (78 + 22, v/v) as the mobile phase and measuring the response at λmax 286 nm. The analysis was performed on a Lichrospher RPC18 column. The calibration curve was obtained for cefixime at 5 to 250 μg/mL, and the mean recovery was 99.71 ± 0.01%. The methods were validated according to the guidelines of the U.S. Pharmacopoeia and also assessed by applying the standard addition technique. The results obtained in the analysis of dosage forms agreed well with the contents stated on the labels.

Stability-Indicating Reversed-Phase Liquid Chromatographic Method for Simultaneous Determination of Simvastatin and Ezetimibe from Their Combination Drug Products

A simple, precise, and rapid stability-indicating reversed-phase column liquid chromatographic (RP-LC) method has been developed and subsequently validated for simultaneous estimation of simvastatin (SIM) and ezetimibe (EZE) from their combination drug product. The proposed RP-LC method utilizes a LiChrospher 100 C18, 5 m, 250 4.0 mm id column at ambient temperature; optimum mobile phase consisting of acetonitrilewatermethanol (60 + 25 + 15, v/v/v) with apparent pH adjusted to 4.0 0.1; mobile phase flow rate of 1.5 mL/min; and ultraviolet detection at 238 nm. SIM, EZE, and their combination drug product were exposed to thermal, photolytic, hydrolytic, and oxidative stress conditions, and the stressed samples were analyzed by the proposed method. There were no other coeluting, interfering peaks from excipients, impurities, or degradation products due to variable stress conditions, and the method is specific for the estimation of SIM and EZE in the presence of degradation products. The described method was linear over the range of 180 and 380 g/mL for SIM and EZE, respectively. The mean recoveries were 99.17 and 100.43 for SIM and EZE, respectively. The intermediate precision data were obtained under different experimental conditions, and the calculated value of the coefficient of variation was found to be less than the critical value. The proposed method can be useful in the quality control of bulk manufacturing and pharmaceutical dosage forms.

APOL1 Polymorphisms in a Deceased Donor and Early Presentation of Collapsing Glomerulopathy and Focal Segmental Glomerulosclerosis in Two Recipients

Two common polymorphisms in APOL1 (G1 and G2) are conserved in persons of African ancestry, and the presence of two polymorphisms (commonly referred to as risk variants) has been identified as a risk factor for chronic kidney disease and focal seg-mental glomerulosclerosis. In kidney transplantation, deceased donors with two APOL1 risk variants carry an increased risk of renal allograft failure in the recipient. An emerging question is whether these data should influence deceased donor assessment or be used to refine prediction of allograft survival. We present the first detailed report of two cases of recipient glomerular disease in the first year following transplant from a deceased donor later defined as carrying two APOL1 risk variants. A possible "second hit" predisposing to renal disease in these recipients is discussed, one with active cytomegalovirus infection concurrent with collapsing glomerulopathy and renal failure and the other with chronic, slowly healing wound infection and focal segmental glomeru-losclerosis but stable renal function. In retrospect, awareness of the donor APOL1 risk alleles would not have influenced donor selection and ultimately did not influence posttransplant management. These case reports inform further discussion of the value of APOL1 testing for deceased donors.

Stability-indicating reversed-phase liquid chromatographic method for simultaneous determination of atorvastatin and ezetimibe from their combination drug products

A simple, precise, and rapid stability-indicating reversed-phase column liquid chromatographic (RP-LC) method has been developed and subsequently validated for simultaneous estimation of atorvastatin (ATV) and ezetimibe (EZE) from their combination drug product. The proposed RP-LC method utilizes a LiChrospher 100 C18, 5 microm, 250 x 4.0 mm id column at ambient temperature; the optimum mobile phase consists of acetonitrile-water-methanol (45 + 40 + 15, v/v/v) with apparent pH adjusted to 4.0 +/- 0.1; mobile phase flow rate of 1.0 mL/min; and UV detection at 250 nm. ATV, EZE, and their combination drug product were exposed to thermal, photolytic, hydrolytic, and oxidative stress conditions, and the stressed samples were analyzed by the proposed method. There were no other coeluting, interfering peaks from excipients, impurities, or degradation products due to variable stress conditions, and the method is specific for the estimation of ATV and EZE in the presence of degradation products. The response was linear over the concentration range of 1-80 microg/mL for ATV and EZE. The mean recoveries were 99.27 and 98.5% for ATV and EZE, respectively. The intermediate precision data were obtained under different experimental conditions, and the calculated value of the coefficient of variation was found to be less than the critical value. The proposed method can be useful in the quality control of bulk manufacturing and pharmaceutical dosage forms.

Stability-indicating reversed-phase liquid chromatographic method for simultaneous determination of simvastatin and ezetimibe from their combination drug products

A simple, precise, and rapid stability-indicating reversed-phase column liquid chromatographic (RP-LC) method has been developed and subsequently validated for simultaneous estimation of simvastatin (SIM) and ezetimibe (EZE) from their combination drug product. The proposed RP-LC method utilizes a LiChrospher 100 C18, 5 microm, 250 x 4.0 mm id column at ambient temperature; optimum mobile phase consisting of acetonitrile-water-methanol (60 + 25 + 15, v/v/v) with apparent pH adjusted to 4.0 +/- 0.1; mobile phase flow rate of 1.5 mL/min; and ultraviolet detection at 238 nm. SIM, EZE, and their combination drug product were exposed to thermal, photolytic, hydrolytic, and oxidative stress conditions, and the stressed samples were analyzed by the proposed method. There were no other coeluting, interfering peaks from excipients, impurities, or degradation products due to variable stress conditions, and the method is specific for the estimation of SIM and EZE in the presence of degradation products. The described method was linear over the range of 1-80 and 3-80 microg/mL for SIM and EZE, respectively. The mean recoveries were 99.17 and 100.43% for SIM and EZE, respectively. The intermediate precision data were obtained under different experimental conditions, and the calculated value of the coefficient of variation was found to be less than the critical value. The proposed method can be useful in the quality control of bulk manufacturing and pharmaceutical dosage forms.

Spectrophotometric, difference spectroscopic, and high-performance liquid chromatographic methods for the determination of cefixime in pharmaceutical formulations

Three simple and sensitive spectrophotometric, difference spectroscopic, and liquid chromatographic (LC) methods are described for the determination of cefixime. The first method is based on the oxidative coupling reaction of cefixime with 3-methyl-2-benzothiazolinon hydrazone HCI in presence of ferric chloride. The absorbance of reaction product was measured at the maximum absorbance wavelength (wavelength(max)), 630 nm. The difference spectroscopic method is based on the measurement of absorbance of cefixime at the absorbance maximum, 268 nm, and minimum, 237 nm. The measured value was the amplitude of maxima and minima between 2 equimolar solutions of the analyte in different chemical forms, which exhibited different spectral characteristics. The conditions were optimized, and Beer's law was obeyed for cefixime at 1 to 16 microg/mL and 10 to 50 microg/mL, respectively. The third method, high-performance LC, was developed for the determination of cefixime using 50 mM potassium dihydrogen phosphate (pH 3.0)-methanol (78 + 22, v/v) as the mobile phase and measuring the response at wavelength(max) 286 nm. The analysis was performed on a Lichrospher RPC18 column. The calibration curve was obtained for cefixime at 5 to 250 microg/mL, and the mean recovery was 99.71 +/- 0.01%. The methods were validated according to the guidelines of the U.S. Pharmacopoeia and also assessed by applying the standard addition technique. The results obtained in the analysis of dosage forms agreed well with the contents stated on the labels.

Stability of rifampicin in dissolution medium in presence of isoniazid

Rifampicin (RIF) hydrolyzes in acidic medium to form insoluble and poorly absorbed 3-Formyl rifamycin SV (3-FRSV). This study describes development of two principally different methods, Dual Wavelength UV-Vis. spectrophotometry (DW spectrophotometry) and HPTLC, to determine 3-FRSV in presence of RIF. Using DW spectrophotometry, RIF was estimated by using wavelengths 475.0 and 507.0 nm and 3-FRSV was estimated using 457.0 and 492.0 nm. In HPTLC method, a mixture of chloroform:methanol:water (80:20:2.5 v/v) was used as the mobile phase to resolve 3-FRSV from RIF and 3-FRSV was quantified at 333 nm. The linearity range for 3-FRSV was 2-10 microg/ml and 50-250 ng/spot for DW spectrophotometric method and HPTLC method, respectively, and 5-50 microg/ml for RIF using DW spectrophotometric method. Both the methods were found to be specific, accurate and reproducible. The proposed methods were successfully applied to determine the rate of degradation of RIF to 3-FRSV in dissolution medium (0.1 N HCl) and also in presence of isoniazid (INH). The rate of degradation of RIF in presence of INH was almost two times more than that of RIF alone. These methods were utilized to study the stability of RIF in market formulations of RIF and RIF with INH in dissolution medium. It has been observed that RIF degrades by 12.4% to form 3-FRSV (RIF formulations) while in presence of INH the degradation is catalyzed to about 21.5% (RIF+INH formulations), in 45 min. Thus, lower concentration of RIF may be available for absorption leading to poor bioavailability of RIF from combination dosage forms (RIF+INH) as compared to formulations containing only RIF. It is proposed that specific analytical method should be used to measure RIF in presence of 3-FRSV in a dissolution study.

The human bone morphogenetic protein 4 (BMP-4) gene: molecular structure and transcriptional regulation

Bone morphogenetic protein 4 (BMP-4) is a vital regulatory molecule that functions throughout human development in mesoderm induction, tooth development, limb formation, bone induction, and fracture repair and is overexpressed in patients who have fibrodysplasia ossificans progressiva. The human gene encoding bone morphogenetic protein 4 (BMP-4) has been isolated and its structural organization characterized. The complete DNA sequence of an 11.2 kb region has been determined. BMP-4 mRNA is transcribed from four exons, although there is evidence that alternate first exons may be used. Transcript initiation occurs at variable positions within a GA-rich region of the DNA. The promoter region is GC-rich with no obvious TATA or CAAT consensus sequences, and contains both positive and negative transcriptional regulatory elements within the 3 kb 5' flanking region of the RNA start site. Comparison of the human and murine BMP-4 genes reveals highly conserved sequences not only in the exon-coding regions but also within the introns and 5' flanking regions. BMP-4 localizes to human chromosome 14q21 by fluorescence in situ hybridization, a location more centromeric than that recently reported. These studies provide a foundation for understanding the genetic regulation of this important gene in human development.

Bivalirudin compared with heparin during coronary angioplasty for thrombus-containing lesions

OBJECTIVES

We investigated whether bivalirudin is more effective than heparin in preventing ischemic complications in high risk patients undergoing coronary angioplasty for thrombus-containing lesions detected by angiography.

BACKGROUND

Heparin is administered during coronary angioplasty to prevent closure of the dilated vessel. Bivalirudin (Hirulog) is a direct thrombin inhibitor that can be safely substituted for heparin during angioplasty. Bivalirudin has several theoretic advantages over heparin as an anticoagulant agent.

METHODS

We performed an observational analysis of the Hirulog Angioplasty Study in which 4,098 patients with unstable or postinfarction angina were randomized to receive either bivalirudin or heparin during coronary angioplasty. The study group for this analysis consisted of 567 patients who had thrombus-containing lesions on angiography. The primary end point was death, myocardial infarction, emergency coronary artery bypass graft surgery or abrupt vessel closure before hospital discharge.

RESULTS

Patients with thrombus-containing lesions had a higher incidence of myocardial infarction (5.1% vs. 3.2%, p = 0.03) and abrupt vessel closure (13.6% vs. 8.3%, p < 0.001) than those without thrombus. In patients with thrombus-containing lesions, however, the incidence of the primary end point was not different between the bivalirudin and heparin treatment groups. Furthermore, no difference in the incidence of ischemic events at 6 months was seen between the treatment groups.

CONCLUSIONS

Bivalirudin is not more effective than heparin in preventing ischemic complications in patients undergoing coronary angioplasty for thrombus-containing lesions detected by angiography. Other approaches, perhaps involving potent anti-platelet agents, should be considered for patients with thrombus-containing lesions.

Water dynamics and population pressure in the Nepalese Himalayas

The authors investigate the impact of water shortages, especially water for irrigation, on development in Nepal. "The problems associated with hydropower development will be illustrated by using the Kulekhani watershed project as a case study." The possible future effects on food supplies and health are discussed.

Rabbit complement lyses tumor cells without massive C3 deposition

These experiments were performed to determine why rabbit complement lyses tumor cells very efficiently, while not having particularly strong activity in hemolytic assays or in any other complement assay. The target cells used were human tumor cells coated with three different mouse IgG(2a) monoclonal antibodies, and complement from 5 mammalian species were tested. In antibody titration experiments, rabbit complement was found to lyse target cells at a relatively low antibody concentration, insufficient to allow lysis by complement of other species. Since this result was still observed after absorption of rabbit serum with target cells, the potency of rabbit complement cannot be attributed to the presence of natural antibodies. We then assayed C3 deposition on target cells, using two types of (125)I-labeled anti-C3 Abs to measure C3 deposition: goat antibodies specific for C3 of the human, guinea pig, rabbit, rat or mouse, and chicken antibodies to human C3 which cross-react with C3 of other mammals. Unexpectedly, complement of the human, rat, guinea pig, and BUB mouse deposited large amounts of C3 on the surface of target cells, while rabbit complement deposited 100-1,000 fold less. We discuss the possible reasons that C3 deposition does not correlate with cytotoxicity, and may indeed be inversely related. These data indicate that there is a fundamental difference in the complement cascade between rabbits and the other species tested. The potent lytic activity of rabbit complement is likely to be related to this difference, although the mechanism is not yet understood.

Spinal deformity in patients who have fibrodysplasia ossificans progressiva

We reviewed roentgenograms and clinical records in order to characterize the spinal deformity in forty patients who had an established diagnosis of fibrodysplasia ossificans progressiva. Twenty-six (65 per cent) of the patients had scoliosis, which, according to the clinical records and the recollection of the patients, had been present during childhood. Twenty-three (88 per cent) of the twenty-six curves were unbalanced c-shaped curves, while the remaining three (12 per cent) were balanced s-shaped curves. Twenty-one (91 per cent) of the twenty-three c-shaped curves involved the thoraco-lumbar or lumbar spine. The c-shaped curves ranged in magnitude from 15 to more than 80 degrees. Curves became rigid by early adulthood and many resulted in severe pelvic obliquity with impaired sitting or standing balance. An osseous bridge developed between the posterolateral aspect of the iliac crest and the posterolateral aspect of the rib cage in twenty-two (55 per cent) of the forty patients. Nineteen (86 per cent) of these twenty-two patients had scoliosis; there was a significant association between the development of scoliosis and the presence of the osseous bridge (p < 0.005). Ossification of the paravertebral muscles and fascia during the first decade of life limited the development of a normal thoracic kyphosis in ten (42 per cent) of twenty-four patients for whom lateral roentgenograms of the spine were available. A spinal orthosis was used to treat the scoliosis in two patients, but this method resulted in breakdown of the skin and failed to halt progression of the curve.(ABSTRACT TRUNCATED AT 250 WORDS)

Correlation between dissolution characteristics and absorption of methaqualone from solid dosage forms

A methaqualone tablet in two strengths, 150 and 300 mg, was developed. The dissolution rate of an experimental formulation in pH 7.0 phosphate buffer, measured by the resin flask method, was shown to correlate with bioavailability in humans. The dissolution rate criterion was used to develop the final tablet formulation. Bioavailability of this formulation in two strengths was compared with a commercial capsule formulation and a slowly dissolving tablet formulation. Correlation between dissolution rate and bioavailability was shown in freshly prepared methaqualone tablet formulations. Bioavailability of tablets under accelerated stability testing conditions remained unaltered, whereas the dissolution rates in pH 7 phosphate buffer decreased, using the resin flask method. A rotating-flask method was developed, and dissolution in 0.1 N HCl at 2 rpm correlated with the bioavailability of both new and aged tablet formulations.