Objective: The present investigation demonstrates a simple, sensitive and accurate high-pressure liquid chromatographic (HPLC) method for simultaneous determination of metaxalone (MTX) and Diclofenac potassium (DIC) in plasma by using Valsartan (VSN) as internal standard. Methods: The chromatographic separation was achieved within 10 min by using methanol: potassium dihydrogen phosphate buffer pH 4.5 adjusted with orthophosphoric acid (60:40) as mobile phase on Altima Grace Smart C-18 column (5μ; 250×4.6 mm) at flow rate of 1.0 ml/min with injection volume 25µl. The drug was extracted from plasma by liquid-liquid extraction using methanol as a solvent. The retention times of drugs (MTX and DIC) and internal standard were found to be 5.83, 9.65 and 11.79 min, respectively. This method was validated as per United States Food and Drug Administration (US-FDA) guidelines. Results: The results of the validation parameters were found to be within the acceptance limits. The method was linear in the concentration range from 25-1000 ng/ml (r2= 0.9998) and the extraction recovery was found to be 77.06% for MTX and 78.37% for DIC. The lower limit of quantification was found to be 25ng/ml and the stability of recovered samples at different conditions were found to be more than 95% for both the drugs. Conclusion: The developed method possesses good selectivity specificity, there was no interference found in the plasma blanks at retention times of MTX and DIC. We found good correlation between the peak area and concentration of the drug under prescribed conditions. Furthermore, the method can also be used to estimate the pharmacokinetic parameters of MTX and DIC simultaneously.

Objective: The present investigation demonstrates a simple, sensitive and accurate high pressure liquid chromatographic (HPLC) method for the determination of alvimopan (AMP) in rat plasma.Methods: The chromatographic separation was achieved within 10 min by using acetonitrile: potassium dihydrogen phosphate buffer pH 3.0 adjusted with orthophosphoric acid (50:50) as mobile phase on Altima Grace Smart C-18 column (5μ; 250 × 4.6 mm) at a flow rate of 1.0 ml/min with injection volume 50 µl. The drug was extracted from plasma by liquid-liquid extraction using a mixture of methanol: acetonitrile (50:50) as a solvent. The retention times of drug and internal standard were found to be 5.17 and 6.74 min, respectively. This method was validated as per the United States Food and Drug Administration (US-FDA) guidelines.Results: The results of the validation parameters were found to be within the acceptance limits. The method was linear in the concentration range from 5-1000 ng/ml (r2= 0.9998), and the extraction recovery was found to be 78.71±3.86% for AMP. The lower limit of quantification was found to be 5ng/ml, and the stability of recovered samples at different conditions was found to be more than 95%.Conclusion: The developed method possess good selectivity, specificity, there was no interference found in the plasma blanks at retention times of AMP and Internal Standard (IS). We found a good correlation between the peak area and concentration of the drug under prescribed conditions. Furthermore, the method can also be used to estimate the pharmacokinetic parameters of AMP.Keywords: Alvimopan, Liquid-liquid extraction, Method development, Matrix effect, Plasma, Recovery, Stability, Validation

Objective: The objective of the present study is to develop and validate a simple, rapid, sensitive reverse phase HPLC method for the determination of Armodafinil present in bulk and its pharmaceutical formulations.Methods: The chromatographic separation was achieved by using Hypersil ODS C-18 (150 x 4.6 mm, 5µ) in an isocratic mode with mobile phase methanol: phosphate buffer 3.0 (60:40 %v/v) was used. The flow rate was 1 ml/min and effluent was monitored at 225 nm. The method was validated for validation parameters i.e. linearity, accuracy, precision and robustness according to ICH guidelines.Results: The retention time of Armodafinil was 4.2 min and the linearity range of the method was 500-20000ng/ml with regression (r2) coefficient 0.9998. The method was validated for precision, accuracy, robustness and which were found to be within the acceptable limits according to the ICH guidelines. Also, the method was successfully applied for the estimation of Armodafinil in the marketed formulation of Nuvigil and the recovery was found to be>98%.Conclusion: The developed method possess good selectivity, specificity, there is no interference found in the blank at a retention time of ARM and good correlation between the peak area and concentration of the drugs under prescribed conditions. Hence, the method can be applied for routine analysis of Armodafinil.Â

A simple, rapid, and precise RP-HPLC method for simultaneous analysis of atorvastatin calcium, metformin hydrochloride, and glimepiride in bulk and its pharmaceutical formulations has been developed and validated. These drugs were separated by using Grace Smart Altima C-8 column (250 × 4.6 mm, 5- μ m) with a mobile phase consisting of acetonitrile : phosphate buffer (60 : 40 (v/v), pH 3.0) at a flow rate of 1 mL/min, injection volume 25  µ L, and detection at 235 nm. Metformin, atorvastatin, and glimepiride were eluted with retention times of 2.57 min, 7.06 min, and 9.39 min, respectively. The method was validated for accuracy, precision, linearity, specificity, and sensitivity in accordance with ICH (Q2B) guidelines. The results of all the validation parameters were found to be within the acceptable limits. The calibration plots were linear over the concentration ranges from 10 to 150  µ g/mL, 20 to 200  µ g/mL, and 10 to 150  µ g/mL for atorvastatin, metformin, and glimepiride, respectively. The accuracy and precision were found to be between 98.2%–105% and ≤2% for three drugs. Developed method was successfully applied for the determination of the drugs in tablet dosage form and recovery was found to be >98% for three drugs. The degradation products produced as a result of stress studies did not interfere with drug peaks.

An isocratic stability indicating RP-HPLC–UV method is presented for the determination of metaxalone (MET) in the presence of its degradation products. The method uses Dr. Maisch C18 column (250mm×4.6mm, 5μm) with mobile phase consisting of acetonitrile–potassium dihydrogen orthophosphate buffer with 4mL of 0.4% triethyl amine (pH 3.0; 10mM) (58:42, v/v) at a flow rate of 1.0mL/min. pH of the buffer was adjusted with o-phosphoric acid. UV detection was performed at 225nm. The method was validated for specificity, linearity, precision, accuracy, limit of detection, limit of quantification and robustness. The calibration plot was linear over the concentration range of 1–100μg/mL having a correlation coefficient (r2) of 0.999. Limits of detection and quantification were 0.3 and 1μg/mL, respectively. Intra-day and inter-day precision (% RSD) was 0.65 and 0.79 respectively. The proposed method was used to investigate the degradation kinetics of MET under different stress conditions employed. Degradation of MET followed a pseudo-first-order kinetics, and rate constant (K), time left for 50% potency (t1/2), and time left for 90% potency (t90) were calculated.

A novel liquid chromatographic-electrospray ionization mass spectrometric (LC-ESI-MS) method has been developed for the determination of Armodafinil in human plasma using carbamazepine as internal standard. The sample was prepared by employing liquid-liquid extraction method from human plasma using ethyl acetate as a solvent. The chromatographic separation was achieved within 3.0 min by using 0.2% formic acid: methanol (15:85) as mobile phase on hypurity advance C-18 column (5 mu; 100 x 4.6 mm) at a flow rate of 1.0 ml/min. Ion signals m/z "274.1/167.3, 237.0/192.0" for armodafinil and internal standard respectively were measured in the positive ion mode. A detailed validation of the method was performed as per US-FDA guidelines (ICH Q2B). The results of all validation parameters were found to be within the acceptance limits. The drug concentration range from 50-10000 ng/mL was shown to be linear (r(2) = 0.9989). Accuracy of the method was found to be > 94%, and lower limit of quantification was found at 50 ng/mL. The extraction recoveries were found to be 70.6 +/- 0.96% and 67.7 +/- 1.32% for ARM and IS, respectively. The recoveries of the stability of sample at different conditions were found to be more than 95%. From the results, it is suggested that the proposed method is simple, reproducible, accurate and precise. So, this method can be applied for the future investigative studies of ARM in human plasma.