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Differential scanning calorimetry (DSC) is a primary technique for measuring the thermal properties of materials, which reflects the physico-chemical properties of drug substances. In the present study, it is used as a screening technique for assessing the compatibility of sitagliptin with some currently employed pharmaceutical excipients. The influence of processing conditions and their effects (simple blending, co-grinding or kneading) on drug stability was evaluated. Sitagliptin showed a sharp endothermic peak at 212.1 °C with an enthalpy change of 131.5 J g−1 indicating melting of drug. Facile transformation of dehydrated sitagliptin to monohydrate form was observed in some mixtures, disappearance of sharp melting endothermic peak of sitagliptin was observed in some mixtures. On the basis of DSC results, sitagliptin was found to be compatible with micro crystalline cellulose, croscarmellose, and pregelatinized starch. Some excipient interaction was observed with magnesium stearate, ascorbic acid, and citric acid. X-ray diffractometry and FT-IR were used as supportive tools in interpreting the DSC results. Overall, the excipients selected were compatible with the API and the mixtures are stable within the tested conditions. These results would be useful for formulation development of the film coated tablets of sitaglitptin.

An isocratic, stability-indicating, reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed for the quantitative determination of doxofylline and terbutaline sulphate, used for the treatment of respiratory problems. The chromatographic separation was achieved on a Zorbax-SB Phenyl 250 x 4.6mm x 5 μm column with the mobile phase consisting of a mixture of 25 mM ammonium acetate (pH 5.0) : acetonitrile (85:15 %v/v) at a flow rate of 1.0 ml/min. The eluate was monitored at 274 nm using a PDA detector. Forced degradation studies were performed on the bulk sample of doxofylline and terbutaline sulphate using acid (0.1N HCl), base (0.1N NaOH), oxidation (10% hydrogen peroxide), photolytic, and thermal degradation conditions. Good resolution was observed between the degradants and analytes. Degradation products resulting from the stress studies did not interfere with the detection of doxofylline and terbutaline sulphate, thus the assay is stability-indicating. The method has the requisite accuracy, selectivity, sensitivity, and precision for the simultaneous estimation of doxofylline and terbutaline sulphate in bulk and pharmaceutical dosage forms. The limit of quantitation and limit of detection were found to be 1.16 μg/ml and 0.38 μg/ml for doxofylline, 2.08 μg/ml and 0.62 μg/ml for terbutaline sulphate, respectively.

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.

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 lim...

Polypill is a fixed dose combination, used as a single daily pill to achieve a large effect in preventing cardiovascular disease with minimal adverse effects. In the present study, gradient LC method was developed for simultaneous determination of the Polycap, that is, Atenolol, Hydrochlorothiazide, Aspirin, Ramipril, and Simvastatin, in presence of their major interaction/degradation products. The individual drug components and their major interaction/degradation products were well separated using reverse phase C18 column and a mobile phase containing Acetonitrile:Phosphate buffer (pH 2.3). Other instrumental parameters were flow rate, 1 mL min−1; detection wavelength, 230 nm; column oven temperature, 40°C; and injection volume, 5 µL. The combined drugs were subjected to stress conditions such as hydrolysis, oxidation, photolysis, and thermal decomposition. The method was validated for linearity, precision, accuracy, specificity, and robustness.

A validated specific stability indicating reversed-phase high-performance liquid chromatography method was developed for the quantitative determination of Amsacrine as well as its related substances determination in bulk samples, in presence of degradation products, and its process related impurities. Forced degradation studies were performed on bulk samples of Amsacrine as per International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human use (ICH) prescribed stress conditions using acid, base, oxidative, thermal stress, and photolytic degradation to show the stability indicating power of the method. Significant degradation was observed during basic hydrolysis, slight degradation was observed in oxidative and thermal stress, and no degradation was observed in other stress conditions. The chromatographic method was optimized using the samples generated from forced degradation studies and the impurity spiked solution. Good resolution between the peaks corresponds to process-related impurities and degradation products from the analyte were achieved on Inertsil ODS column using the mobile phase consists a mixture of 1.0% triethyl amine in 20 mM potassium dihydrogen orthophosphate, with pH adjusted to 6.5, with ortho phosphoric acid in water and acetonitrile using a simple linear gradient. The detection was carried out at wavelength 248 nm. The mass balance in each case was in between 99.4% to 99.9%, indicating that the developed method was stability-indicating. Validation of the developed method was carried out as per ICH requirements. The developed method was found to be suitable to check the quality of bulk samples of Amsacrine at the time of batch release and also during its stability studies.

A novel, sensitive and precise UHPLC method has been developed and validated for the simultaneous determination of the all the active components of a Polypill viz Zycad, i.e., Aspirin (ASP) Atorvastatin (ATV), Ramipril (RMP) and Metoprolol (MTP) in Zycad tablet dosage form in the presence of degradation products. Forced degradation of individual as well as combination of all the drug substances components of Polypill was conducted in accordance with ICH guidelines. Acidic, basic, neutral, and oxidative hydrolysis, thermal stress, and photolytic degradation were used to assess the stability-indicating power of the method. Use of 100 × 2.1 mm, 1.7 µm stationary phases with simple mobile phase combination buffer consisting of 0.1% Perchloric acid (adjusted to pH 2.5) and Acetonitrile, delivered in a gradient mode and quantitation was carried out using ultraviolet detection at 215 nm with a flow rate of 0.6 mL?min–1. The method was optimized using samples generated by forced degradation studies. The method was validated for linearity, accuracy (recovery), precision, Specificity and robustness. The method was linear in the range of 37.5 to 150.0 µg?mL–1 for ASP, 5.0 to 20.0 µg?mL–1 for ATV and 2.5 to 10.0 µg?mL–1 for RMP and 25.0 to 100.0 µg?mL–1 for MTP.

Summary A new, sensitive, stability-indicating, and cost and time-effective isocratic reversed-phase UHPLC method has been developed for quantitative analysis of felbamate, an antiepileptic drug, both in the bulk drug and in pharmaceutical dosage forms. Chromatographic separation of felbamate and its two impurities was achieved on a C18 column with a simple buffer-methanol mobile phase; the run time was 8 min. Quantification was achieved by ultraviolet detection. Resolution between the impurities was >2.0. Response was a linear function of concentration over the range 0.1–3.0 μg mL−1, correlation coefficient >0.999, for felbamate and the impurities. The method is capable of detecting the two impurities at levels of 0.002% (0.02 μg mL−1) of the test concentration of 1.0 mg mL−1 (1 μL injection). The same sensitivity was achieved for all the degradation products formed during stress studies in which the drug was subjected to hydrolysis, oxidation, photolysis, and thermal degradation. Substantial degradation...

A novel, sensitive, stability indicating RP-LC method has been developed for the quantitative determination of mitotane, its impurity in both bulk drugs and pharmaceutical dosage forms. Efficient chromatographic separation was achieved using a C18 stationary phase with simple mobile phase combination delivered in an isocratic mode and quantitation was by ultraviolet detection at a wavelength of 230 nm. The mobile phase consisted of buffer and acetonitrile (25:75, v/v) delivered at a flow rate of 1.0 mL min−1. Buffer consisted of 10 mM potassium dihydrogen orthophosphate monohydrate, pH adjusted to 2.5 by orthophosphoric acid. In the developed LC method the resolution (Rs) between mitotane and its impurity namely Imp-1 was found to be greater than 2.5. Regression analysis shows an r value (correlation coefficient) greater than 0.999 for mitotane and its impurity. This method was capable to detect the impurity of mitotane at a level of 0.003% with respect to test a concentration of 0.2 mg mL−1 for a 10 μL injection volume. The inter- and intra-day precision values for mitotane and its impurity was found to be within 2.0% RSD. The method has shown good and consistent recoveries for mitotane in bulk drugs (99.2–101.5%), pharmaceutical dosage forms (98.2–103.1%) and for its impurity (99.7–102.1%). The test solution was found to be stable in diluent for 48 h. The drug was subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal degradation. Considerable degradation was found to occur in basic stress hydrolysis. The stress samples were assayed against a qualified reference standard and the mass balance was found close to 99.97%. The developed RP-LC method was validated with respect to linearity, accuracy, precision and robustness.

A new, sensitive, stability indicating gradient RP-LC related substances and assay method has been developed for the quantitative determination of entacapone in bulk drugs. Efficient chromatographic separation was achieved on a C18 stationary phase with simple mobile phase combination of buffer and acetonitrile. Buffer consisted of 0.1% orthophosphoric acid, delivered in a gradient mode and quantitation was carried out using ultraviolet detection at 220 nm with a flow rate of 1.5 mL min−1. In the developed LC method the resolution (Rs) between entacapone and its three potential process impurities were found to be >2.0. Regression analysis showed an r2 value (correlation coefficient) >0.99 for entacapone and its three potential impurities. This method was capable to detect all three process impurities of entacapone at a level of 0.003% with respect to test concentration of 0.5 mg mL−1 for a 20 μL injection volume. The inter- and intra-day precision values for all three impurities and for entacapone was found to be within 2.0% RSD. The method has shown good and consistent recoveries for entacapone in bulk drugs (99.2–101.5%) and its three impurities (99.5–102.2%). The test solution was found to be stable in diluent for 48 h. The drug substances were subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal degradation. Considerable degradation was found to occur in acid stress, base stress and oxidative conditions. The stressed test solutions were assayed against the qualified working standard of entacapone and the mass balance in each case was close to 99.7% indicating that the developed method was stability-indicating. The developed RP-LC method was validated with respect to linearity, accuracy, precision and robustness.

A novel, sensitive, stability-indicating gradient RP-LC method has been developed for quantitative analysis of balsalazide disodium and its related impurities both in the bulk drug and in pharmaceutical dosage forms. Efficient chromatographic separation was achieved on a C18 stationary phase with a simple mobile-phase gradient prepared from methanol and phosphate buffer (10 mm potassium dihydrogen orthophosphate monohydrate, adjusted to pH 2.5 by addition of orthophosphoric acid). The mobile-phase flow rate was 1.0 mL min−1. Quantification was achieved by use of ultraviolet detection at 240 nm. Under these conditions resolution of balsalazide disodium from its three potential impurities was greater than 2.0. Regression analysis resulted in a correlation coefficient greater than 0.99 for balsalazide disodium and all three impurities. This method was capable of detecting the three impurities at 0.003% of the test concentration of 0.3 mg mL−1, using an injection volume of 10 μL. Inter-day and intra-day precision for all three impurities and for balsalazide disodium was within 2.0% RSD. Recovery of balsalazide disodium from the bulk drug (99.2–101.5%) and from pharmaceutical dosage forms (99.8–101.3%), and recovery of the three impurities (99.1–102.1%) was consistently good. The test solution was found to be stable in 70:30 (v/v) methanol–water for 48 h. When the drug was subjected to hydrolytic, oxidative, photolytic, and thermal stress, acidic and alkaline hydrolysis and oxidizing conditions led to substantial degradation. The RP-LC method was validated for linearity, accuracy, precision, and robustness.

A simple, sensitive gradient RP-LC assay method has been developed for the quantitative determination of vardenafil HCl in bulk drug and in pharmaceutical dosage forms, used to treat erectile dysfunction. The developed method is also applicable for the related substances determination. Efficient chromatographic separation was achieved on a C18 stationary phase with simple mobile phase combination delivered in a gradient mode and quantification was carried out using ultraviolet detection at a flow rate of 1.0 mL min−1. In the developed LC method the resolution between vardenafil and its four potential impurities was found to be greater than 3.0. Regression analysis shows an r2 value (correlation coefficient) greater than 0.99 for vardenafil and its four impurities. This method was capable of detecting all four impurities of vardenafil at a level of 0.009% with respect to test concentration of 1.0 mg mL−1 for a 10 μL injection volume. The method has shown good and consistent recoveries for vardenafil (98.4–100.6%) and its four impurities (93.5–106.2%). The test solution was found to be stable in the diluent for 48 h. Mass balance was found close to 99.4%.

A simple, sensitive gradient RP-LC assay method has been developed for the quantitative determination of amtolmetin guacyl in bulk drug, used as anti-inflammatory drug. The developed method is also applicable for related substances determination. Efficient chromatographic separation was achieved on a C18 stationary phase with simple mobile phase combination delivered in a gradient mode and quantification was carried out using ultraviolet detection at 313 nm at a flow rate of 1.0 mL min−1. In the developed LC method the resolution between Amtolmetin Guacyl and its three potential impurities was found to be greater than 2.0. Regression analysis shows an r value (correlation coefficient) greater than 0.99 for amtolmetin guacyl and its three impurities. This method was capable to detect all three impurities of amtolmetin guacyl at a level of 0.002% with respect to test concentration of 0.5 mg mL−1 for a 10 μL injection volume. The inter- and intra-day precision values for all three impurities and for amtolmetin guacyl was found to be within 2.0% RSD at its specification level. The method has shown good and consistent recoveries for amtolmetin guacyl (99.2–101.5%) and its three impurities (94.5–104.8%). The test solution was found to be stable in diluent for 48 h. The drug was subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal degradation. Considerable degradation was found to occur in oxidative stress conditions. The stress samples were assayed against a qualified reference standard and the mass balance was found close to 99.6%. The developed RP-LC method was validated with respect to linearity, accuracy, precision and robustness.

A new and accurate chiral liquid chromatographic method has been developed for the separation and quantification of (S,R,S)-enantiomer (unwanted enantiomer) and (R,R,R)-isomer (key intermediate) of aprepitant in bulk drug and formulation samples of apprepitant. The elution time was approximately 20 min using an immobilized amylose-based chiral stationary phase (Chiralpak-IA). The mobile phase was n-hexane and ethanol (90:10, v/v) and was delivered at a flow rate of 1.0 mL min−1. Detection was carried out with a wavelength set to 220 nm. The resolution factor between enantiomers was found to be greater than five. Limit of detection for both (S,R,S) enantiomer and (R,R,R) isomer of aprepitant was 0.035 µg, and limit of quantification for both (S,R,S) enantiomer and (R,R,R) isomers of aprepitant was 0.1 µg, for a 10 µL injection. The developed method showed excellent linearity (r > 0.999) for both isomers. When the method was applied to bulk drug samples and in pharmaceutical formulations recoveries were obtained ranging from 97.2 to 103.1%. Aprepitant sample solutions were found to be stable when characterized over a period of 48 h.

A new and accurate chiral liquid chromatographic method has been developed for determination of the enantiomeric purity of montelukast sodium (R enantiomer) in bulk drugs and dosage forms. Normal phase chromatographic separation was performed on an immobilized amylose-based chiral stationary phase with n-hexane–ethanol–1,4-dioxane–trifluoroacetic acid–diethylamine 65:25:10:0.3:0.05 (v/v) as mobile phase at a flow rate of 1.0 mL min−1. The elution time was approximately 15 min. The resolution (RS) between the enantiomers was >3. The mobile phase additives trifluoroacetic acid and diethylamine played a key role in achieving chromatographic resolution between the enantiomers and also in enhancing chromatographic efficiency. Limits of detection and quantification for the S enantiomer were 0.07 and 0.2 μg, respectively, for a test concentration of montelukast sodium of 1,000 μg mL−1 and 10 μL injection volume. The linearity of the method for the S enantiomer was excellent (R2 > 0.999) over the range from the LOQ to 0.3%. Recovery of the S enantiomer from bulk drug samples and dosage forms ranged from 97.0 to 103.0%, indicative of the high accuracy of the method. Robustness studies were also conducted. The sample solution stability of montelukast sodium was determined and the compound was found to be stable for a study period of 48 h.