134SIMULTANEOUS ESTIMATION OF MELATONIN AND ZOLPIDEM IN TABLETS DOSAGE FORMS BY RP-HPLC METHODA new, simple, specific, rapid, accurate, and precise reverse phase HPLC method was developed for simultaneous estimation melatonin and zolpidem, in pharmaceutical dosage forms. They were chromatographic on a reverse phase Column – C 18(Enable C18 G) (250 mm x 4.6mm, 5µ), in a mobile phase consisting of dibasic potassium hydrogen phosphate buffer (0.05M) adjust to pH 6.5 with phosphoric acid and acetonitrile in the ratio 65:35.The flow rate of 1ml/min detection at 230nm. The retention time 3.59 and 7.48 of melatonin and zolpidem respectively. The detector response was linear in the concentration of (192-288 µg/ml) for Melatonin and (320-480µg/ml) for Zolpidem respectively. The limit of detection melatonin and zolpidem was found to 43.34µg/mL-1 and 40.49µg/mL-1. The limit of quantification was 131.34µg/mL-1 and 122.84µg/mL-1 .The developed method was validated in terms of accuracy, precision, linearity, limit of detection, limit of quantification and system suitability as per ICH guidelines.kg.lalitha@gmail.comResearch342012Melatonin,Zolpidem RP- HPLC method development,ValidationVenkatachalam T,Lalitha KGDepartment of Pharmaceutical Chemistry, JKKMMRF College of Pharmacy, B.Komarapalayam-638183, Tamil Nadu, India.,Department of Pharmaceutical Chemistry, Ultra College of Pharmacy, Madurai-625020. Tamil Nadu