Utilization of N-bromosuccinimide for the sensitive spectrophotometric determination of pipazethate HCl as antitussive drug in pure and dosage forms.

OBJECTIVES: Three simple, sensitive, precise, reproducible and validated spectrophotometric methods have been developed for the quantification of pipazethate HCl as antitussive drug in pure and dosage forms. METHODS: The methods are based on utilization of N-bromosuccinimide as an oxidant and three dyes, amaranth, methylene blue, and indigo carmine, as auxiliary reagents. The proposed methods are based on oxidation reaction of pipazethate HCl with a known excess of N-bromosuccinimide in acid medium, followed by determination of unreacted N-bromosuccinimide by the reaction with a fixed amount of dyes, amaranth, methylene blue, and indigo carmine followed by the measurement of the absorbance at 520, 663 and 610nm, respectively. The optimization of the reaction conditions was investigated. RESULTS: Under the optimum conditions, linear relationships with good correlation coefficients (0.9998-0.9999) were found over the concentration ranges of 0.3-9.0, 0.5-12 and 0.5-10µgmL-1 with a limit of detection (LOD) of 0.1, 0.15 and 0.15µgmL-1 using amaranth, methylene blue, and indigo carmine methods, respectively. Intra-day and inter-day accuracy and precision of the methods have been evaluated. No interference was observed from the common tablet excipients. CONCLUSION: The developed methods were validated in accordance with ICH guidelines and successfully applied to the analysis of pipazethate HCl in dosage forms with good accuracy and precision. The reliability of the methods was further ascertained by performing recovery studies via the standard addition method. Statistical comparison of the results obtained by applying the proposed methods with those of the reported method by applying Student's t-test and variance ratio F-test at the 95% confidence level revealed good agreement and indicates no significant difference in accuracy and precision.

Sensitive spectrophotometric determination of vardenafil HCl in pure and dosage forms.

OBJECTIVES: The present work aims to develop and validate a simple, rapid, cost-effective, sensitive and extractive spectrophotometric methods for the determination of phosphodiesterase type 5-inhibitor; vardenafil HCl (VARD) in pure and in dosage forms. METHODS: The developed methods are based on the formation of ion-pair complexes between vardenafil HCl and dyes, namely, bromocresol green (BCG), bromocresol purple (BCP), bromophenol blue (BPB), bromothymol blue (BTB) and eriochrom black T (EBT) in acidic buffer solutions. Different factors affecting the reactions between VARD and the dyes were studied and optimized. RESULTS: The formed complexes were extracted with methylene chloride and measured at 418, 410, 415, 417 and 520nm using BCG, BCP, BPB, BTB and EBT, respectively. The beer's law was obeyed in the ranges 1.0-10, 1.0-16, 0.5-8.0, 2.0-20 and 1.0-14µgmL-1 for BCG, BCP, BPB, BTB and EBT, respectively under the optimum conditions. The composition of the ion-pairs was found 1:1. The molar absorptivity's, Sandell's sensitivity, limits of detection and the limits of quantification were calculated. Other method validation parameters, such as accuracy, intra-day and inter-day precision, robustness, ruggedness and selectivity, have been evaluated. CONCLUSION: The proposed methods have been applied successfully for the analysis of vardenafil HCl in pure and dosage forms. The reliability of the methods was further ascertained by performing recovery studies using the standard addition method. Statistical comparison of the results with the reported method was performed by applying student's t- and F-tests and no significant statistical differences were obtained.

Development and validation of spectrophotometric methods for estimation of antimigraine drug eletriptan hydrobromide in pure form and pharmaceutical formulations.

OBJECTIVES: The present study aims to develop and validate four simple, sensitive, reproducible, and low-cost spectrophotometric methods for the determination of antimigraine drug (eletriptan hydrobromide) in pure form and pharmaceutical formulations. METHODS: The methods are based on the formation of yellow colored ion-pair complex between eletriptan hydrobromide and four acid dyes, namely, bromocresol purple (BCP), bromocresol green (BCG), bromophenol blue (BPB), and bromothymol blue (BTB) with absorption maxima at 410, 420, 414 and 416nm, respectively. Several parameters such as pH, buffer type and volume, reagent volume, sequence of addition and effect of extracting solvent were optimized. RESULTS: Under the optimum experimental conditions, beer's law is obeyed over the concentration ranges of 1.0-20 and 1.0-16µgmL-1 for (BCP or BCG) and (BPB or BTB), respectively with good correlation coefficients (0.9995-0.9999). The apparent molar absorptivity and Sandell's sensitivity values are reported for all methods. The limit of detection (LOD) and the limit of quantification (LOQ) values are found to be 0.27, 0.28, 0.25, and 0.30µgmL-1 and 0.90, 0.93, 0.83, and 1.0µgmL-1 for BCP, BCG, BPB and BTB, respectively. The stoichiometric ratio of the formed ion-pair complexes was found to be 1:1 (drug: reagent) for all methods. CONCLUSION: The developed methods were successfully applied for the determination of eletriptan hydrobromide in pharmaceutical formulations with good accuracy and precision. Statistical comparison of the results was performed using Student's t-test and variance ratio F-test at the 95% confidence level and there was no significant difference between the reported and proposed methods regarding accuracy and precision. Further, the validity of the proposed methods was confirmed by recovery studies via standard addition method.