RP-HPLC Method for the Simultaneous Determination of a Quaternary Mixture of Propyphenazone, Flavoxate HCl and Two of Their Official Impurities with Dissolution Profiling of Their Tablets.

BACKGROUND: Determination of different drugs in the presence of their impurities is now receiving attention from regulatory authorities such as the ICH and the United States Food and Drug Administration (USFDA). OBJECTIVE: To develop and validate a reversed-phase (RP)-HPLC method for the simultaneous separation and quantification of a quaternary mixture of propyphenazone, flavoxate HCl, and their official impurities; phenazone and 3-methylflavone-8-carboxylic acid, respectively. Then utilize the validated method as an in vitro methodology to monitor the rate of release of the active ingredients from Cistalgan® tablets. METHODS: RP-HPLC method was applied using Kinetex® coreshell C8 column (250 mm × 4.6 mm I.D., particle size 5 µm) and acetonitrile: phosphate buffer pH 3.50 (42:58, v/v) as the mobile phase with UV detection at 240.0 nm. RESULTS: The studied components were eluted with average retention times of 2.80, 3.40, 4.20, and 5.90 min for phenazone, flavoxate HCl, 3-methylflavone-8-carboxylic acid, and propyphenazone, respectively within linearity range of 1.00-60.00 µg/mL propyphenazone, 3.00-60.00 µg/mL flavoxate HCl and 0.50-40.00 µg/mL of the specified impurities. CONCLUSIONS: The suggested method could be considered as the first validated analytical method for the simultaneous determination of the studied components and proved to be accurate, precise, sensitive, and robust. HIGHLIGHTS: The proposed method displays a useful analytical tool for dissolution profiling and clear discrimination of both active ingredients from their impurities along with impurities profiling.

Simultaneous Determination of Moxifloxacin and Flavoxate by RP-HPLC and Ecofriendly Derivative Spectrophotometry Methods in Formulations.

Simple, fast, and precise reversed-phase (RP)-high-performance liquid chromatography (HPLC) and two ecofriendly spectrophotometric methods were established and validated for the simultaneous determination of moxifloxacin HCl (MOX) and flavoxate HCl (FLX) in formulations. Chromatographic methods involve the separation of two analytes using an Agilent Zorbax SB C18 HPLC column (150 mm × 4.6 mm; 5 µm) and a mobile phase consisting of phosphate buffer (50 mM; pH 5): methanol: acetonitrile in a proportion of 50:20:30 v/v, respectively. Valsartan was used as an internal standard. Analytes were monitored by measuring the absorbance of elute at 299 nm for MOX and 250 nm for FLX and valsartan. Two environmentally friendly spectrophotometric (first derivative and ratio first derivative) methods were also developed using water as a solvent. For the derivative spectrophotometric determination of MOX and FLX, a zero-crossing technique was adopted. The wavelengths selected for MOX and FLX were -304.0 nm and -331.8 nm for the first derivative spectrophotometric method and 358.4 nm and -334.1 nm for the ratio first-derivative spectrophotometric method, respectively. All methods were successfully validated, as per the International Conference on Harmonization(ICH) guidelines, and all parameters were well within acceptable ranges. The proposed analytical methods were successfully utilized for the simultaneous estimation of MOX and FLX in formulations.

Liquid chromatographic fingerprint of 3-methylflavone-8-carboxylic acid established for its synthesis control analysis.

A high-performance liquid chromatographic method was proposed for the separation of relative impurities in industrial 3-methylflavone-8-carboxylic acid (MFCA) and its intermediate methyl 3-propionylsalicylate (MPS). Benzoic acid (BA), MPS, 6-chloro-3-methylflavone-8-carboxylic acid (MFCA-Cl) and methyl 5-chloro-3-propionylsalicylate (MPS-Cl) in MFCA, and MPS-Cl in MPS were respectively quantified by an external standard method. As results showed, the linearity of standard curves was excellent with the relative coefficients of over 0.999 for all the detected components, and the intra- and inter-day precisions of impurities determination were satisfactory with the relative standard deviation of not more than 8.0%. Under the selected experimental condition, the chromatographic fingerprints of MFCA and MPS were drawn synthetically, and the transfer of impurities in the stepwise reactions of MFCA manufacture was elucidated. The fingerprints have great potential in instructing the production of MFCA for industrial use and in conducting the conversion of relative impurities.

High-performance liquid chromatographic determination of flavoxate hydrochloride and its hydrolysis product.

Liquid chromatographic method was presented for the determination of flavoxate hydrochloride (FX) and its hydrolysis product. The method was based on high-performance liquid chromatographic (HPLC) separation of FX from its hydrolysis product on CN column using a mobile phase consisting of acetonitrile-12 mM ammonium acetate (45:55, vol/vol, pH 4.0) with UV detection at 220 nm and flow rate of 1.5 mL min(-1). The proposed HPLC method for the determination of FX was utilized to investigate the kinetics of acidic hydrolytic process at different temperatures and to calculate its activation energy. In addition, the proposed HPLC method was used for pH-rate profile study of hydrolysis of FX in Britton-Robinson buffer solutions. The 3-methylflavone-8-carboxylic acid ethyl ester, as impurity of flavoxate hydrochloride, can be separated by the proposed HPLC method.

Polymeric matrix membrane sensors for stability-indicating potentiometric determination of oxybutynin hydrochloride and flavoxate hydrochloride urogenital system drugs.

Four polyvinyl chloride (PVC) matrix membrane electrodes responsive to 2 drugs affecting the urogenital system--oxybutynin hydrochloride (OX) and flavoxate hydrochloride (FX)--were developed, described, and characterized. A precipitation-based technique with tungstophosphate (TP) and ammonium reineckate (R) anions as electroactive materials in a PVC matrix with an OX cation was used for electrode 1 and 2 fabrication, respectively. Electrode 3 and 4 fabrication was based on use of the precipitation technique of FX cation with tetrakis (4-chlorophenyl) borate and R anions as electroactive materials. Fast and stable Nernstian responses in the range 1 x 10(-2)-1 x 10(-6) M for the 2 drugs over the pH range 5-8 revealed the performance characteristics of these electrodes, which were evaluated according to International Union of Pure and Applied Chemistry recommendations. The method was applied to FX and OX in their pharmaceutical formulations and in human plasma samples. The 4 proposed sensors were found to be specific for the drugs in the presence of up to 60% of their degradation products. Validation of the method according to the quality assurance standards showed suitability of the proposed electrodes for use in the quality control assessment of these drugs. The recoveries for determination of the drugs by the 4 proposed selective electrodes were 99.5 +/- 0.5, 100.0 +/- 0.4, 99.9 +/- 0.4, and 100.1 +/- 0.4% for sensors 1-4, respectively. Statistical comparison between the results obtained by this method and the official method of the drugs was done, and no significant difference found.

High performance liquid chromatographic determination of 3-methylflavone-8-carboxylic acid, the main active metabolite of flavoxate hydrochloride in human urine.

High performance liquid chromatographic (HPLC) method was presented for the determination of 3-methylflavone-8-carboxylic acid as the main active metabolite of flavoxate hydrochloride (FX) in human urine. The proposed method was based on using CN column with mobile phase consisting of acetonitrile-12 mM ammonium acetate (40:60, v/v) and adjusted to apparent pH 4.0 with flow rate of 1.5 ml min(-1). Quantitation was achieved with UV detection at 220 nm. The proposed method was utilized to the determination of dissolution rate for tablets containing flavoxate hydrochloride. The urinary excretion pattern has been calculated using the proposed method.

Structural characterization of terflavoxate.

Data are reported on the structural characterization of 3-methyl-4-oxo-2-phenyl-4H-1-benzopyran-8-carboxylic acid 1,1-dimethyl-2-(N-piperidinyl)ethyl ester hydrochloride (terflavoxate-HCl, Rec 15/2053, CAS 86433-39-8), a new antispasmodic for the lower urinary tract. UV, IR, NMR and MS spectra fully confirmed the structure. The X-ray crystal structure determination revealed that the molecular structure consists of a rigid platform, formed by the chromone system, with two arms, the phenyl group at C(2) and the ester chain at C(8). The ester chain conformation generates a small hollow where two oxygen atoms face.