A simple, specific, accurate and stability indicating reversed phase high performance liquid chromatographic method was developed for the simultaneous determination of atorvastatin calcium and amlodipine besylate in tablet dosage forms. A phenomenex Gemini C-18, 5 μm column having 250×4.6 mm i.d. in isocratic mode, with mobile phase containing 0.02 M potassium dihydrogen phosphate:acetonitrile:methanol (30:10:60, v/v/v) adjusted to pH 4 using ortho phosphoric acid was used. The flow rate was 1.0 ml/min and effluents were monitored at 240 nm. The retention times of atorvastatin calcium and amlodipine besylate were 11.6 min and 4.5 min, respectively. The calibration curves were linear in the concentration range of 0.08-20 μg/ml for atorvastatin calcium and 0.1-20 μg/ml for amlodipine besylate. Atorvastatin calcium and amlodipine besylate stock solutions were subjected to acid and alkali hydrolysis, chemical oxidation and dry heat degradation. The degraded product peaks were well resolved from the pure drug peak with significant difference in their retention time values. The proposed method was validated and successfully applied to the estimation of atorvastatin calcium and amlodipine besylate in combined tablet dosage forms.

An isocratic, reversed phase-liquid-chromatographic assay method was developed for the quantitative determination of ibuprofen and famotidine in combined-dosage form. A Brownlee C 18 , 5μm column with mobile phase containing water : methanol : acetonitrile (30 : 60 : 10, v/v/v) was used. The flow rate was 1.0 mL/min, and effluents were monitored at 264 nm. The retention times of ibuprofen and famotidine were 4.9 min and 6.8 min, respectively. The linearity for ibuprofen and famotidine was in the range of 2-20 μg/mL and 0.1-10 μg/mL, respectively. The proposed method was validated with respect to linearity, accuracy, precision, specificity, and robustness. The method was successfully applied to the estimation of ibuprofen and famotidine in combined dosage form.

A simple, precise, accurate, and economical spectrophotometric method has been developed for simultaneous estimation of levocetirizine dihydrochloride (LCT) and phenylephrine hydrochloride (PHE) by employing first-order derivative spectrophotometric method. The first-order derivative absorption at 240 nm (zero crossing point of PHE) was used for quantification of LCT and 283.2 nm (zero crossing point of LCT) for quantification of PHE. The linearity was established over the concentration range of 4-24 g/mL and 8-48 g/mL for LCT and PHE with correlation coefficients ( 2 ) 0.9964 and 0.9972, respectively. The mean % recoveries were found to be in the range of 99.14%-100.43% for LCT and 98.73%-100.83% for PHE. The proposed method has been validated as per ICH guideline and successfully applied for the simultaneous estimation of LCT and PHE in combined tablet dosage form.

A simple, sensitive, precise and stability indicating liquid chromatographic method has been developed for the estimation of desvenlafaxine succinate in pharmaceutical dosage form. A Hypersil C-18, 5 μm-column with a mobile phase containing 0.05 M potassium dihydrogen phosphate:methanol (60:40 v/v), pH 7, was used. The flow rate was 1.0 mL/min and effluents were monitored at 226 nm. The retention time of desvenlafaxine was 7.4 min and the method was linear in the range of 0.1-20 µg/mL. Desvenlafaxine stock solution was subjected to acid and alkali hydrolysis, chemical oxidation and dry heat degradation. The drug was found to be susceptible to base hydrolysis and developed method was found to give good separation between the pure drug and the degraded product. The method was successfully applied to the estimation of desvenlafaxine in tablet dosage forms.Desvenlafaxine succinate (DVX) is chemically RS-4-[2-dimethylamino-1-(1-hydroxycyclohexyl)ethyl]-phenol succinate monohydrate. It is a salt form of the major active metabolite of venlafaxine. Desvenlafaxine inhibits serotonergic and noradrenergic reuptake receptors with minimal affinity for muscarinic, cholinergic, histaminergic, and α 1 -adrenergic receptors [1]. Desvenlafaxine lacks monoamine oxidase inhibitory activity. Serotonergic receptors are inhibited approximately 10-fold more than noradrenergic receptors. Based on the in vitro results and the relationship between desvenlafaxine and venlafaxine, desvenlafaxine is classified as a selective serotonin and norepinephrine reuptake inhibitor (SNRI). Approximately 75% of venlafaxine is metabolized into O-desmethylvenlafaxine or desvenlafaxine by the action of CYP2D6 on parent drug [2]. Desvenlafaxine is not predominately metabolized by the cytochrome P450 (CYP) system and is eliminated primarily by phase II metabolism; as a result, it has lower potential for drug interactions, especially with the CYP 2D6 pathway. It has been approved for the treatment of major depressive disorder (MDD) and has also been studied for the treatment of vasomotor symptoms associated with menopause [3][4]. Preliminary evidence also suggests the clinical usefulness of DVX in the treatment of anxiety symptoms, and painful physical symptoms [5][6].A literature survey regarding quantitative analysis of the drug revealed that attempts have been made to develop analytical methods for the estimation of DVX in human plasma using HPLC with fluorescence detection [7][8][9], HPLC with UV detection [10], LC-MS/MS [11][12][13] and HPLC-ESI/MS [14].The International Conference on Harmonization (ICH) guidelines [15] require the implementation of stress testing procedures for the identification of degradation products that are potentially occurring in drug substances which can help to understand the possible degradation pathway for the drug. The apparent lack of a method for the estimation of desvenlafaxine in pharmaceutical dosage form prompted us to develop an accurate, specific and sensitive liquid chromatographic method. EXPERIMENTAL ApparatusThe ...

Two simple and accurate methods for analysis of nebivolol hydrochloride (NEB) and hydrochlorothiazide (HCTZ) in their combined dosage forms were developed using first-order derivative spectrophotometry and reversed-phase liquid chromatography (LC). NEB and HCTZ in their combined dosage forms (tablets) were quantified using first-derivative responses at 294.6 and 334.6 nm in the spectra of their solutions in methanol. The calibration curves were linear in the concentration range of 840 g/mL for NEB and 1060 g/mL for HCTZ. LC analysis was performed on a Phenomenex Gemini C18 column (250 4.6 mm id, 5 m particle size) in the isocratic mode with 0.05 M potassium dihydrogen phosphateacetonitrilemethanol (30 + 20 + 50, v/v/v; pH 4) mobile phase at a flow rate of 1 mL/min. Detection was made at 220 nm. Both of the drugs and the internal standard (ezetimibe) were well resolved with retention times of 5.1 min for NEB, 2.9 min for HCTZ, and 8.2 min for ezetimibe. The calibration curves were linear in the concentration range of 114 g/mL for NEB and 0.328 g/mL for HCTZ. Both methods were validated and found to be accurate, precise, and specific, and results were compared statistically. Developed methods were successfully applied for the estimation of NEB and HCTZ in their combined dosage forms.