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Summary.A simple, sensitive, and precise high-performance liquid chromatographic (HPLC) method for quantitation of montelukast in human plasma has been developed and validated. Commercially available candesartan cilexetil was used as an internal standard. After protein precipitation, montelukast and candesartan cilexetil (I.S.) in human plasma were analyzed using mobile phase containing 62% v/v acetonitrile and 38% v/v buffer (containing 1 mL L −1 triethylamine as peak modifier, final pH adjusted to 2.5 with orthophosphoric acid). Chromatographic separation was achieved on a BDS Hypersil-C18 column (50 × 4.6 mm i.d., particle size 5 μm; Thermo Electron Corporation, USA) using isocratic elution at a flow rate of 1.5 mL min −1 . The signals were monitored using a fluorescence detector set at 350 nm for excitation and 400 nm for emission. The total time for a chromatographic separation was ~3 min. The validated quantitation ranges of this method were 5-300 ng mL −1 with coefficients of variation between 1.75% and 9.38%. Mean recoveries were 91.8 ± 3.8%. The within-and between-batch precisions were 0.74-2.46% and 1.64-7.87%, respectively. The within-and between-batch relative errors (bias) were 0.14-3.3% and 0.08-4.6%, respectively. Stability of montelukast in plasma was >94.7%, with no evidence of degradation during sample processing and 30 days storage in a deep freezer at -70°C. This validated method is sensitive and simple with between-batch precision of <8% and successfully applied for the bioequivalence studies. The formulations were compared using the following pharmacokinetic parameters: AUC 0−t , AUC 0−∞ , and C max . No statistically significant difference (p > 0.05) was observed between the logarithmically transformed AUC 0−t, AUC 0−∞ , and C max values.