Application of Lean Six Sigma and Quality tools plays an important role in interpretation of the data of quality attributes, decreasing waste time, remission manpower and reducing variation which will give intensity, confidence, and thoroughness. Thus, one can follow up and assure that the Process Capability Index (Cpk) is >1.33 and still capable during the all stages of the product. The purposes of this work are: to develop and validate a simple, accurate, precise and new RP-HPLC and UPLC methods, after reconstitution, accelerated stability and comparative in vitro dissolution studies. These were proceeded for the simultaneous determination of cefdinir (CFR) and sodium benzoate (SDM), respectively in the generic product; Dinar 125 mg / 5 mL powder for oral suspension (POS) and Dinar 300 mg capsule (CAP) and consequently it had been considered equivalent to the innovator product; Omnicef 125 mg / 5 mL POS and Omnicef 300 mg CAP using FDA media of 0.05 M phosphate buffer having pH 6.8. The chromatographic separation and resolution were performed at ambient temperature using: a) Agilent Eclipse XDB C8 column (250 mm X 4.6 mm, 5 μm particle size) with a mobile phase consisting of acetonitrile: 0.05 M phosphate buffer solution pH 4.5 (50:50 v/v) at flow rate of 1.0 mL /minute, injection volume 10 µL for RP-HPLC. b) Waters CORTECS ® C18 column (50 mm X 4.6 mm, 2.7 μm particle size) at flow rate 0.3 mL/min and injection volume 0.3 μL for RP-UPLC. UV detection at 254 nm was used with correlation coefficients (r) >0.999 for CFR and SDM, respectively. The method was validated according to ICH guidelines.