Validated spectrofluorimetric and resonance Rayleigh scattering methods for determining naftidrofuryl in varied pharmaceutical samples based on its interaction with erythrosin B.

Naftidrofuryl is a vasodilator medication used for treating cerebral and peripheral vascular diseases. In this study, two spectroscopical techniques, spectrofluorimetric and resonance Rayleigh scattering (RRS), were utilized to quantify naftidrofuryl in its pharmaceutical samples. The developed methodologies in this study rely on a facile process of forming an association complex between erythrosine B reagent and naftidrofuryl under acidic conditions. The fluorimetric assay is based on the ability of naftidrofuryl to quench and decrease the native fluorescence intensity of the reagent when measured at λ emis . = 550 nm ( λ excit . = 526 nm). Under similar reaction conditions, the RRS method relies on the observed amplification in the RRS spectrum of the reagent at a wavelength of 577 nm following its interaction with naftidrofuryl. The methods exhibited linearity within the ranges 0.2-1.6 µg/ml (r2  = 0.999) and 0.1-1.4 µg/ml (r2  = 0.9994), with limit of quantitation values of 0.146 and 0.099 µg/ml, and limit of detection values of 0.048 and 0.032 µg/ml, for the fluorometric and the RRS methods, respectively. Moreover, the quenching between the dye and naftidrofuryl was studied using Stern-Volmer analysis, and the methodologies were experimentally optimized and validated. Additionally, acceptable recoveries were achieved when the procedures were applied to determine naftidrofuryl in pharmaceutical samples.

Application of π acceptors to the spectrophotometric and spectrofluorimetric determination of vincamine and naftidrofuryl oxalate in their pharmaceutical preparations.

Three different spectrophotometric and two spectrofluorimetric methods have been developed and validated for the determination of vincamine (VN) and naftidrofuryl oxalate (NF) in tablets. The spectrophotometric methods depend on charge transfer complex formation between each of VN and NF with 7,7,8,8-tetracyano-quinodimethane (TCNQ), 2,6-dichloroquinone-4-chloroimide (DCQ) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) at 843, 580 and 588 nm, respectively. The spectrofluorimetric methods are based on the formation of charge transfer complex between each of the two drugs and TCNQ, with measurement of the fluorophore formed at 312/375 and 284/612 nm, respectively, or with DDQ at 400/475 and 284/396 nm, respectively. In the spectrophotometric measurements, Beer's law was obeyed at concentration ranges of 1.5-16, 10-180 and 12-140 µg/ml for VN with TCNQ, DCQ, and DDQ, respectively. For NF, the corresponding concentrations were 2-28, 5-75 and 25-150 µg/ml with TCNQ, DCQ, and DDQ, respectively. In the spectrofluorimetric measurements, the ranges for VN were 0.05-0.9 and 0.3-4 µg/ml with TCNQ and DDQ, respectively, whereas for NF the ranges were 0.05-0.85 and 0.5-8 µg/ml with TCNQ and DDQ, respectively. The different experimental parameters affecting the development and stability of the formed color or fluorophore were studied and optimized and the molar ratios of the complexes were calculated. The proposed methods were validated according to ICH guidelines and were successfully applied for the determination of VN and NF in their tablet dosage forms.

A validated HPLC method for the simultaneous determination of naftidrofuryl oxalate and its degradation product (metabolite), naftidrofuryl acid: applications to pharmaceutical tablets and biological samples.

A simple, sensitive, and selective reverse phase-high performance liquid chromatography (RP-HPLC) method was developed and validated for the simultaneous determination of naftidrofuryl oxalate (NF) and its hydrolytic degradation product (metabolite), naftidrofuryl acid (NFA). Chromatographic separation was achieved on Spheri-5 RP-C8 (5 µm) (220 × 4.6 mm i.d.) column using a mobile phase composed of acetonitrile, 0.05 M sodium acetate and triethylamine (40 : 60 : 0.1, by volume) adjusted to pH 5.5 using glacial acetic acid. The mobile phase was pumped at flow rate 1.5 ml/min. The UV detector was set at 225 nm and quantification of the analytes was based on measuring the peak areas. The method was proved to be accurate and precise with linearity ranges of 0.1-25 and 0.2-25 µg ml(-1) for NF and NFA, respectively. The limits of detection were 0.03 and 0.04 µg ml(-1) for NF and NFA, respectively. The method was applied to serve three goals: (1) stability-indicating assay of the parent drug NF in its pharmaceutical formulation, (2) determination of the degradation product NFA down to a level of 0.005% in the presence of large excess of the parent drug, and (3) drug monitoring of naftidrofuryl and its metabolite, naftidrofuryl acid, in human plasma/urine samples taken from a healthy volunteer treated with 200 mg oral dose of naftidrofuryl oxalate. The proposed method proved to be accurate, precise, and reliable in all these application fields.

Fatal intoxication with naftidrofuryl.

A 52-year-old man was found dead in his bed. He had financial and psychosocial problems like separation from his wife and children or unemployment due to alcoholism. Under treatment of disulfiram he was presently abstinent from alcohol. As he had suffered from epileptic seizures and dizziness, he received valproic acid and the vasodilator naftidrofuryl, respectively. Autopsy showed no morphologic cause of death. Chemical analysis of blood revealed concentrations for valproic acid and disulfiram in the therapeutic and above the therapeutic range but far below the lethal level, respectively. No ethanol was found. However, the very high concentration of 7500 microg/L naftidrofuryl in whole blood was considered as cause of death, and the most probable manner of death seemed to be suicide. To our knowledge, this is the first reported case of a fatal poisoning with naftidrofuryl.

Facile and selective determination of the cerebral vasodilator nafronyl in a commercial formulation by heavy atom induced room temperature phosphorimetry.

This paper presents a facile and selective method for the determination of the pharmaceutical compound nafronyl using heavy atom induced room temperature phosphorimetry (HAI-RTP) as analytical technique. The determination was performed in potassium iodide 1.6 M and sodium sulphite 0.002 M at a measurement temperature of 20 degrees C. The phosphorescence intensity was then measured at lambda(exc) = 292 nm and lambda(em) = 524 nm. Phosphorescence was fully developed instantly, obtaining a linear concentration range between 2.7 and 250 ng ml(-1) with the detection limit of 2.7 ng ml(-1), an analytical sensitivity of 5.1 ng ml(-1) and a standard deviation of 2.17%, at a 150 ng ml (-1) concentration level. The proposed method has been satisfactorily applied to the unique Spanish commercial formulation containing nafronyl at a 100 mg level per capsule. The recovery was 108%, with a 1.7%, standard deviation of the analytical measurement. The method has been validated using standard addition methodology.

Determination of nafronyl in pharmaceutical preparations by means of stopped-flow micellar-stabilized room temperature phosphorescence.

The stopped-flow mixing technique was applied to micellar-stabilized room temperature phosphorimetry by measuring the fast appearance of the phosphorescent signal yielded by nafronyl in the presence of sodium dodecyl sulfate and thallium nitrate. This mixing system diminishes the time required for the deoxygenation of micellar medium by sodium sulfite, allowing a kinetic curve that levels off within only 5 s to be obtained. Phosphorescence enhancers thallium(I) nitrate, sodium dodecyl sulfate and sodium sulfite were optimized to obtain maximum sensitivity and selectivity. A pH value of 10.5 was selected as adequate for phosphorescence development. Two rapid, straightforward and automatic methods were proposed using the slope and amplitude of the kinetic curve, which are directly proportional to the nafronyl concentration, as analytical parameters. Calibration graphs were linear for the concentration range from 30 to 600 ng ml-1. Praxilene, the only commercial formulation containing nafronyl, was analysed by both proposed methodologies. Suitable recovery values were obtained.

Prediction of stability in pharmaceutical preparations XVIII: application of high-pressure liquid chromatographic assays to study of nafronyl stability and bioanalysis.

Specific, sensitive, reversed-phase high-pressure liquid chromatographic assays of nafronyl (I) and its acidic metabolite and hydrolysis product (II) were developed in aqueous solutions and in biological fluids with sensitivities of 100 ng/ml using butacaine as the internal standard and spectrophotometric detection of 224 nm. Heparinized plasma can be analyzed easily in the organic phase immediately after acetonitrile denaturation. Both I and II can be extracted with haloalkane solvents, and the extracts are evaporated, reconstituted, and assayed in a minimal amount of acetonitrile. Conditions are presented that minimize the interference of II and extracted plasma components. The assay was used to determine the stability of nafronyl in aqueous solutions, to establish its log k-pH profiles at various temperatures, and to evaluate the Arrhenius parameters. Nafronyl is hydrolyzed by specific hydrogen-ion (15.2 kcal/mole) and hydroxide-ion (7.72 kcal/mole) catalysis of the neutral species and specific hydroxide-ion catalysis (5.91 kcal/mole) of the protonated species. The pH of maximum stability is 3.0, and pH 5.4 is the maximum that can be tolerated at 30 degrees, with a 10% solvolysis in 3 years. The half-life of nafronyl at 30 degrees was 7 days at pH 7, 12 hr at pH 10, and 21 min in 0.5 N NaOH. Since nafronyl has a half-life of 3.2 hr in heparinized dog plasma at 25 degrees, blood samples for pharmacokinetic studies of nafronyl must be assayed immediately after sampling. The partition coefficients of I and II determined as functions of pH permit the extraction of both compounds at pH 4.5, but only I can be extracted at pH values above 9.5.