Cephalexin is a first-generation cephalosporin with an antibacterial spectrum similar to that of cephalothin, but its antibacterial activity is poorer than that of the latter. Except for Enterococcus and methicillin-resistant Staphylococci, most strains of Streptococcus pneumoniae, hemolytic Streptococcus, and Staphylococcus aureus that produces or does not produce penicillinase are sensitive to this product. This product has a good antibacterial effect on Neisseria, but Haemophilus influenzae is less sensitive to this product; this product has a certain antibacterial effect on some Escherichia coli, Proteus mirabilis, Salmonella and Shigella. The remaining Enterobacteriaceae, Acinetobacter, Pseudomonas aeruginosa, and Bacteroides fragilis are resistant to this product. Fusobacterium and Veillonella are generally sensitive to this product, and anaerobic Gram-positive cocci are moderately sensitive to this product.

This product is a broad-spectrum semi-synthetic cephalosporin antibiotic. Its activity against penicillinase-producing Staphylococcus aureus, group A hemolytic streptococci, viridans streptococci and Staphylococcus epidermidis is the same as that of cefadroxil, and its antibacterial effect against non-enzyme-producing Staphylococcus aureus and pneumococci is 2 to 4 times stronger than that of cefadroxil. Its activity against Gram-negative bacilli, including Escherichia coli and Klebsiella pneumoniae, is stronger than that of cefadroxil, and is similar to that of cefadroxil. Its activity against Proteus mirabilis, Salmonella and Shigella is stronger than that of cefadroxil. 2.9 to 8 mg/L of this product can inhibit all Haemophilus influenzae, including strains resistant to ampicillin. Moraxella catarrhalis and Neisseria gonorrhoeae are very sensitive to this product. Indole-positive Proteus, Serratia, Acinetobacter and Pseudomonas aeruginosa are all resistant to this product. The mechanism of action of this product is to inhibit the synthesis of bacterial cell walls.

This product is an anti-anemia drug. Vitamin B12 participates in methyl conversion and folic acid metabolism in the body, and promotes the conversion of 5-methyltetrahydrofolate into tetrahydrofolate. When it is deficient, it leads to DNA synthesis disorders and affects the maturation of red blood cells. This product also promotes the conversion of methylmalonic acid into succinic acid and participates in the tricarboxylic acid cycle. This effect is related to the synthesis of nerve myelin lipids and the maintenance of the integrity of myelinated nerve fiber function. The nerve damage caused by vitamin B12 deficiency may be related to this.

It has a wide range of antibacterial effects on both Gram-positive and Gram-negative bacteria, especially on Streptococcus and Pneumococcus among Gram-positive bacteria, and Gonorrhea, Borrelia, Escherichia coli, Serratia, Klebsiella, Proteus, and Haemophilus influenzae among Gram-negative bacteria. Since the β-lactamase produced by various bacteria is extremely stable, it also has excellent antibacterial properties against bacteria that produce β-lactamase, and its mechanism of action is mainly to prevent the synthesis of bacterial cell walls.