About Cefalexin A first-generation cephalosporin antibiotic. Mechanism of Action Cephalexin is a 1st generation cephalosporin which exerts its bactericidal action against both gram positive & gram negative organisms by inhibiting bacterial cell wall synthesis. Cephalexin inhibits transpeptidase & thus prevents cross linking of bacterial cell wall. Transpeptidase & associated proteins constitute various types of specific binding proteins which have affinity for cephalosporins like Cephalexin Indications for Cefalexin 1.Respiratory tract infections 2.Urinary tract infections 3.Surgical prophylaxis 4.Skin infections` 5.Joint & bone infections 6.Otitis media` 7.Reproductive tract infections` Contra-indications 1.Hypersensitivity to cephalosporins 2.Porphyria 3.Neuromuscular disorders.