A simple, rapid, and stability-indicating RP-HPLC method for a combination of tenofovir disoproxil fumarate (TDF), emtricitabine (FTC), and efavirenz (EFV) was developed and validated with the help of a suitable statistical software as an application tool for the quality by design. The drugs individually, and in combination, were subjected to forced degradation (thermal, photolytic, hydrolytic, and oxidative stress conditions) and accelerated stability studies (40 ± 1°C/75 ± 3% RH for three months). Successful separation of combined drugs from degradation products was achieved by gradient elution on a reverse-phase C18 column, using a mobile phase containing phosphate buffer (pH 3.5): acetonitrile at 1.5 mL min−1 flow rate, detection wavelength 256 nm, column oven temperature 25°C, and injection volume 10 μL. Linearity was established in the range of 20–300 μg mL−1, 24.5–367.5 μg mL−1 and 60–900 μg mL−1 for FTC, TDF, and EFV, respectively. The method was successfully applied for quantifying the drugs in marketed dosage forms and on stability samples.

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Polypill is a fixed-dose combination (FDC) containing three or more drugs in a single pill with the intention of reducing the number of tablets or capsules that need to be taken. Developing a single analytical method for the estimation of individual drugs in a Polypill is very challenging, due to the formation of drug-drug and drug-excipients interaction impurities. Here an attempt was made to develop a new, sensitive, single stability-indicating HPLC method for the simultaneous quantitative determination of Aspirin (ASP) Atorvastatin (ATV), Atenolol (ATL) and Losartan potassium (LST) in a polypill form in the presence of degradation products. Efficient chromatographic separation was achieved on a C18 stationary phase with simple mobile phase combination of buffer and Acetonitrile. Buffer consists of 0.1% Orthophosphoric acid (pH 2.9), delivered in a gradient mode and quantitation was carried out using ultraviolet detection at 230 nm with a flow rate of 1.0 mL/min. The retention times of Atenolol, Aspirin, Losartan potassium, and Atorvastatin were 3.3, 7.6, 10.7 and 12.9 min respectively. The combination drug product are exposed to thermal, acid/base hydrolytic, humidity and oxidative stress conditions, and the stressed samples were analyzed by proposed method. The method was validated with respect to linearity; the method was linear in the range of 37.5 to 150.0 µg/mL for ASP, 5.0 to 20.0 µg/mL for ATV and 25.0 to 100.0 µg/mL for ATL and LST. Acceptable precision and accuracy were obtained for concentrations over the standard curve ranges. The validated method was successfully applied to the analysis of Starpill tablets constituting all the four drugs; the percentage recoveries obtained were 99.60% for ASP, 99.30% for ATV, 99.41% for ATL and 99.62% for LST.

Summary.A simple, rapid, precise, and accurate, stability-indicating reversed phase high performance liquid chromatographic method was developed and validated for simultaneous determination of metformin HCl and repaglinide. The chromatographic separation was achieved on YMC Pack AM ODS (5 μm, 250 mm length × 4.6 mm i.d.) column at a detector wavelength of 210 nm, using an isocratic mobile phase consisting of methanol and 10 mM potassium dihydrogen phosphate buffer (pH 2.5) in a ratio of 70:30 v/v at a flow rate of 1 mL min −1 . The retention times for metformin and repaglinide were found to be 2.6 and 11.3 min, respectively. The drugs were exposed to thermal, photolytic, hydrolytic, and oxidative stress conditions, and the stressed samples were analyzed by the proposed method. Validation of the method was carried out as per International Conference on Harmonization (ICH) guidelines. Linearity was established for metformin and repaglinide in the range of 5-200 μg mL −1 and 1-200 μg mL −1 , respectively. The limits of detection were 0.3 μg mL −1 and 0.13 μg mL −1 for metformin and repaglinide, respectively. The method was found to be specific and stability-indicating as no interfering peaks of degradants and excipients were observed. The proposed method is hence suitable for application in quality-control laboratories for quantitative analysis of both the drugs individually and in combination, since it is simple and rapid with good accuracy and precision.