Development and validation of a rapid capillary electrophoresis method for the determination of oseltamivir phosphate in Tamiflu® and generic versions

Behaviours of antiviral Oseltamivir in different media: DFT and SQMFF calculations

The synthetic cyclohexenecarboxylate ester antiviral Oseltamivir (O) have been theoretically studied by B3LYP/6–311 +  + G** calculations to estimate its reactivity and behaviour in gas and aqueous media. The most stable structure obtained in above media is consistent with that reported experimental for Oseltamivir phosphate. The solvation energy value of (O) in aqueous media is between the predicted for antiviral Idoxuridine and Ribavirin. Besides, (O) containing a NH₂ group and NH group reveals lower solvation energy compared with other antiviral agents with an NH₂ group, such as Ribavirin, Cidofovir, and Brincidofovir. Atomic charges on N and O atoms in acceptors and donor groups reveal different behaviours in both media, while the natural bond orbital (NBO) studies show a raised stability of (O) in aqueous solution. This latter resulted is in concordance with the lower reactivity evidenced in water. Frontier orbital studies have revealed that (O) in gas phase has a very similar gap value to antiviral Cidofovir used against the ebola disease, while Chloroquine in the two media are more reactive than (O). This study will allow to identify (O) by using vibrational spectroscopy because the 144 vibration modes expected have been assigned using the harmonic force fields calculated from the scaled mechanical force field methodology (SQMFF). Scaled force constants for (O) in the mentioned media are also reported for first time. Due to hydration of the C = O and NH₂ groups by solvent molecules, the calculations in solution produce variations not only in the IR wavenumbers bands, but also in their intensities.

A comparative study of HPLC and UV spectrophotometric methods for oseltamivir quantification in pharmaceutical formulations

Oseltamivir is an antiviral drug and is used in the treatment of all influenza viruses. It is the most effective antiviral option against all influenza viruses that can infect humans. UV and LC methods have been developed and validated according to ICH guidelines for various parameters like selectivity, linearity, accuracy, precision, LOD and LOQ, robustness for the quantitative determination of oseltamivir in pharmaceutical formulations. LC method has been performed using reverse phase technique on a C-18 column with a mobile phase consisting of 20 mM potassium dihydrogen phosphate solution and acetonitrile (60:40, v/v) at 25 °C. The mobile phase flow rate was 1.2 mL min−1. For the determination of oseltamivir, UV spectrum has been recorded between 200 and 800 nm using methanol as solvent and the wavelength of 215 nm has been selected. Both methods have demonstrated good linearity, precision and recovery. No spectral and chromatographic interferences from the capsule excipients were found in UV and LC methods. In both methods, correlation coefficients were greater than 0.999 within a concentration range of 10–60 mg mL−1 using UV and LC. Intra-day and inter-day precision with low relative standard deviation values were observed. The accuracy of these methods was within the range 99.85–100.17% for LC and from 99.26 to 100.70% for UV. Therefore UV and LC methods gave the most reliable outcomes for the determination of oseltamivir in pharmaceutical formulation.

Development and validation of a stability-indicating spectrofluorimetric method for the determination of H1N1 antiviral drug (oseltamivir phosphate) in human plasma through the Hantzsch reaction

A simple and sensitive spectrofluorimetric method has been described and validated for the determination of oseltamivir phosphate (OSP) in its pure form and pharmaceutical dosage forms.

A novel coated platinum electrode for oseltamivir determination in pharmaceuticals

New coated platinum selective electrodes have been prepared and used for the determination of oseltamivir phosphate (OSL) in bulk drug solutions and in pharmaceutical preparations. Electrodes were using plasticized PVC membranes doped with ion-pair complexes based on drug-phosphomolybdate and drug-tetraphenylborate as electroactive materials. The influence of membrane composition (plasticizers and ion-pair complexes) has been investigated. Optimum performance was obtained for two polymeric membranes: PVC:o-NPPE:OSL-TPB in the ratio of 30:68:2 (%, w:w:w) and PVC:DPP:OSL-PMA in the ratio of 30:68:2 (%, w:w:w). The electrodes exhibited linear responses over large concentration ranges (1.0×10(-5)-1.0×10(-2) and 5.0×10(-5)-5.0×10(-2)M, respectively) with near-Nernstian responses (58.9 and 57.3mV/decade, respectively). The selectivity coefficients indicated good selectivity for OSL drug over a large number of organic compounds and some inorganic cations. The proposed electrodes were successfully applied to the determination of OSL in raw material and in pharmaceutical formulations. The results were validated by comparison with a capillary electrophoresis method.

Spectrofluorimetric determination of oseltamivir phosphate through derivatization with o-phthalaldehyde. Application to pharmaceutical preparations with a preliminary study on spiked plasma samples

A simple and sensitive spectrofluorimetric method has been developed and validated for the determination of oseltamivir phosphate (OST) in pharmaceutical preparations. The method is based on the reaction between oseltamivir phosphate and o-phthalaldehyde in presence of 2-mercapto-ethanol in borate buffer, pH 10.8, to give a highly fluorescent product measured at 450 nm after excitation at 336 nm. The different experimental parameters affecting the development and stability of the reaction product were studied and optimized. The fluorescence intensity-concentration plot is rectilinear over the range 0.05-1.0 µg/mL, with a lower detection limit of 5 ng/mL and limit of quantitation of 16 ng/mL. The developed method was successfully applied to the analysis of the drug in its commercial capsules and suspension, mean recoveries of OST were 99.97 ± 1.67% and 100.17 ± 1.18%, respectively (n = 3). Statistical comparison of the results obtained by the proposed and comparison method revealed no significant difference in the performance of the two methods regarding accuracy and precision. The proposed method was further extended to in vitro determination of the studied drug in spiked human plasma as a preliminary investigation; the mean recovery (n = 3) was 98.68 ± 5.8%. A reaction pathway was postulated.

The qualitative determination of oseltamivir phosphate in Tamiflu® capsule by cyclic voltammetry

A gold electrode was applied in the voltammetric determination of oseltamivir phosphate standard in 0.05 M NaHCO3. Oseltamivir phosphate as a standard and as a component of Tamiflu? capsule exhibited the identical cyclic voltammogram. The peaks originated from excipients in capsule do not appear under the applied electrochemical conditions. The electrochemical method for the qualitative determination of oseltamivir phosphate in Tamiflu? capsule by cyclic voltammetry was developed. The presence of oseltamivir phosphate as standard and as a content of Tamiflu? capsule in electrolyte as well as their concentrations were simultaneously checked by HPLC. The lack of the current/concentration dependency was established. The not pretreated glassy carbon electrode cannot be used for the determination of oseltamivir phosphate under identical experimental conditions presented for gold electrode.

Counterfeit drugs and other products and substances: Review of drugs for influenza prevention and treatment including pandemic influenza A(H1N1) 2009

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