INTRODUCTION Cefixime trihydrate (CEF) is an orally active third generation semi synthetic cephalosporin. Chemically, CEF is (6R,7R)- [(Z)-2- (2-aminothiazol-4-yl) -2-[(carboxymethoxy) imino] acetyl]amino]-3-ethenyl-8-oxo-5-thia-1-azabicyclo [4.2.0]pet-2-ene-2-carboxylic acid trihydrate, [Figure1.a] CEF is official in USP, 1 BP, 2 and EP. 3 Moxifloxacin (MOX) (1-cyclopropyl-6-fluoro-1,4- ORIENTAL JOURNAL OF CHEMISTRY www.orientjchem.org Est. 1984 An International Open Free Access, Peer Reviewed Research Journal ISSN: 0970-020 X CODEN: OJCHEG 2012, Vol. 28, No. (4): Pg. 1743-1750 Simultaneous Estimation of Cefixime and Moxifloxacin in Bulk and its Pharmaceutical Dosage form by RP-HPLC G.S. DEVIKA 1 *, M. SUDHAKAR 1 and J. VENKATESHWARA RAO 2 1 Department of Pharmaceutical Chemistry, Malla Reddy College of Pharmacy, Maissamaguda, Dullapally, Secunderabad -14, India. 2 Departmentof Pharmaceutical Chemistry, Sultan Ul Uloom College of Pharmacy, Banjara Hills, Secunderabad - 500 034, India. *Corresponding author E-mail: devikasubramaniyan@gmail.com (Received: October 15, 2012; Accepted: November 20, 2012) ABSTRACT A simple, efficient and reproducible reverse phase high performance liquid chromatographic method was developed and validated for the Simultaneous determination of cefixime (CEF) and moxifloxacin (MOX) in combined dosage form. Chromatographicseparationofthetwo drugswasperformedonaPurospherBDSC18 column(250mm×4.6mmid, 5μm particlesize). The mobile phase comprising of acetonitrile and 0.01M KH 2 PO 4 in a ratio of 40:60 v/v at a flow rate of 1.0ml/min. The detection was made at 276 nm. The retention time of cefixime and moxifloxacin was found to be 3.140± 0.007min and 7.007± 0.006min. Calibration curve was linear over the concentration range of 20-120 μg/ml for both cefixime and moxifloxacin .All the analytical validation parameters were determined and found in the limit as per ICH guidelines, which indicate the validity of the method. The developed method is also found to be precise, accurate, specific, robust and rapid for the simultaneous determination of cefixime and moxifloxacin in tablet dosage forms. Key words: Cefixime, Moxifloxacin, Method development and validation, RP-HPLC. dihydro-8-methoxy-7- [(4aS,7aS)-octahydro-6H- pyrrolo-[3,4-b]pyridin-6-yl]-4-oxo-3-quinoline carboxylic acid hydrochloride) ,[Figure1.b] is new, fourth generation fluoroquinolone with broaden spectrum of antibacterial activity 4-6 . Moxifloxacin in combination with the 3 rd generation cephalosporine cefixime shows great additive and Synergistic effect to treat infectious diseases caused by a Gram-positive or Gram-negative pathogen like Streptococcus pneumoniae, Pseudomonas