BackgroundOmbitasvir/paritaprevir/ritonavir/dasabuvir (Viekira Pak®) are the newest medicines approved for use in the treatment of hepatitis C virus (HCV) and are available in tablet form as an oral combination. Specifically, these agents are indicated in the treatment of HCV in patients with genotype 1 infection. Due to the therapeutic importance and increased use of Viekira Pak, proper methods for its determination in bulk and pharmaceutical formulations must be developed.ResultsThe present study describes the development and validation of a simple, rapid, selective and economical reverse phase high performance liquid chromatography-diode array detection (HPLC-DAD) method for the simultaneous determination of paritaprevir (PAR), ombitasvir (OMB), dasabuvir(DAS) and ritonavir (RIT) in bulk and pharmaceutical preparations. The proposed method was carried out using an RPC18 column (150 × 4.5 mm, 3.5 μ), with a mobile phase consisting of 10 mM phosphate buffer (pH 7)and acetonitrile (35:65, v/v) at a flow rate of 1 ml/min and a detection wavelength of 254 nm. Sorafenib (SOR) was selected as the internal standard to ensure that the quantitative performance was high. The method was validated based on its specificity, linearity, limit of detection, limit of quantitation, accuracy, precision, robustness and stability. The calibration curves for PAR, DAS, RIT and OMB were linear at 2.5–60, 1.25–30, 1.7–40 and 0.42–10 μg/ml, respectively, and all of the correlation coefficients were >0.999.ConclusionsThe proposed method was successfully applied for the determination of ombitasvir/paritaprevir/ritonavir/dasabuvirin tablets, without interference from the excipient peaks. Hence, the method can be applied for the routine quality control analysis of the studied drugs, either in bulk or dosed forms.Graphical abstractSimultaneous estimation of newly developed antiviral agents in pharmaceutical formulations by HPLC-DAD method

Studies were carried out to investigate the charge-transfer (CT) reaction of ROS-Ca, as a n-electron donor with various π-acceptors: tetracyanoethylene, p-chloranilic acid, 2, 3-dichloro-5,6-dicyano-1,4-benzoquinone, 2,3,5,6-tetrabromo-1,4-benzoquinone, 1,3,5-trinitrobenzene, 2,3,5,6-tetrachloro-1,4-benzoquinone, 7,7,8,8-tetracyano-quinodimethane, and 2,4,7-trinitro-9-fluorenone. Different colored CT complexes were obtained. The reaction mechanism and site of interaction were determined by ultraviolet-visible spectrophotometric techniques and computational molecular modeling. The formation of the colored complexes was utilized in the development of simple, rapid and accurate spectrophotometric methods for the determination of ROS-Ca. Under the optimum reaction conditions, linear relationships with good correlation coefficients (0.9984-0.9995) were found between the absorbances and the concentrations of ROS-Ca in the range of 2-200 μg mL . No interference could be observed from the additives commonly present in the tablets or from the drugs that are co-formulated with ROS-Ca in its combined formulations. The methods were successfully applied to the analysis of tablets with good accuracy and precision; the recovery percentages ranged from 99.54-100.46 ± 1.58-1.82%. The results were compared favorably with the reported method. The proposed methods are practical and valuable for OPEN ACCESSMolecules 2013, 18 7712 routine application in quality control laboratories for determination of ROS-Ca in its bulk form and tablets.

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Residues of oxytetracycline, tetracycline and chlortetracycline in seafood products of Saudi Arabia were detected by using a simple, sensitive and rapid method via HPLC-PDA. The protein precipitation method that was used for sample extraction demonstrated high recoveries of OTC, TC and CTC. The limits of detection were 0.015 µg/g and 0.025,0.062 µg/g for all TCs in fish and shellfish, respectively. The limits of quantitation were 0.125 µg/g and 0.175 µg/g for all TCs in fish and shellfish, respectively. The method was precise and accurate since the RSD was less than 2%, while the % recovery was 95–105%. This study determined the occurrence of OTC, TC and CTC in seafood products that are sold in KSA’s markets. The overall occurrence of these three medications in 249 seafood products was 24%(n = 60), while 15%(n = 37) exceeded the MRL. Thus, our recommendations are to enhance the monitoring of food production prior to marketing and to educate people regarding the proper disposal of antibiotics.

A novel method was developed for the simultaneous determination of guaifenesin (GUA) and ketorolac tromethamine (KET) enantiomers in plasma samples. Since GUA probably increases the absorption of coadministered drugs (e.g., KET), it would be extremely important to monitor KET plasma levels for the purpose of dose adjustment with a subsequent decrease in the side effects. Enantiomeric resolution was achieved on a polysaccharide-based chiral stationary phase, amylose-2, as a chiral selector under the normal phase (NP) mode and using ornidazole (ORN) as internal standard. This innovative method has the advantage of the ease and reliability of sample preparation for plasma samples. Sample clean-up was based on simply using methanol for protein precipitation followed by direct extraction of drug residues using ethanol. Both GUA and KET enantiomers were separated using an isocratic mobile phase composed of hexane/isopropanol/trifluoroacetic acid, 85:15:0.05 v/v/v. Peak area ratios were linear over the range 0.05-20 µg/mL for the four enantiomers S (+) GUA, R (-) GUA, R (+) KET, and S (-) KET. The method was fully validated according to the International Conference on Harmonization (ICH) guidelines in terms of system suitability, specificity, accuracy, precision, robustness, and solution stability. Finally, this procedure was innovative to apply the rationale of developing a chiral high-performance liquid chromatography (HPLC) procedure for the simultaneous quantitative analysis of drug isomers in clinical samples.

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