and cephalexin [internalstandard] were separated on a reversed phase column [Merck, Purospher RP-C18, 30 X 4.6 [mm] , 3 micro m] using a mobilephase consisting of an aqueous solution of formic acid in water [0.10 %] and acetonitrile [85: 15 v/v [%] , flow rate0.50 [mL/min.] . Detection utilized a tandem MS/MS, the analytes were ionized using an ESI source in the positive ionmode prior to detection and analysis using Multiple Reaction Monitoring mode [MRM] . The analytes were monitoredat the following transitions [m/z] 396.10 [right arrow] 226.90, and [m/z] 348.24 [right arrow] 158.10 for cefdinir and cephalexinrespectively. Cefdinir linearity was demonstrated over the concentrations ranging from 10 to 1200 [ng/ mL] . Thedeveloped method was fully validated prior to its application on a bioequivalence study involving cefdinir [125 mg/5ml] suspension in healthy volunteers [N= 26] under fasting conditions