Cefathiamidine is a first-generation cephalosporin antibacterial agent and is used to treat infections caused by susceptible bacteria. Cefathiamidine exhibits a wide spectrum of antimicrobial activity against bacteria. Cefathiamidine is used for the treatment of respiratory, liver, five senses, urinary tract infections, endocarditis and sepsis^[1][2]. IC50 & Target: Bacterial^[1] In Vitro: The in-vitro activity of Cefathiamidine against Streptococcus faecalis and Streptococcus faecium are studied in comparison with other β-lactams. All the 56 strains of Str. faecalis tested are inhibited by 2 mg/L of Cefathiamidine. The MBCs of Cefathiamidine and Ampicillin for ten strains of Str. faecalis show that the ratios of MBC/MIC are greater than 64. The rates of killing of Str. faecalis are reduced at concentrations of Cefathiamidine and Ampicillin greater than the MIC. The most rapid killing is obtained at 2 mg/L Cefathiamidine or 4 mg/L of Ampicillin. With the addition of 1 mg/L gentamicin this paradoxical bacteriocidal effect is eliminated. Time killing studies show99.9% of the cells are killed within 6 hours by a combination of aminoglycoside and β-lactam^[2]. In Vivo: Cefathiamidine is not absorbed orally and is, thus, administered through the parenteral route (intravenously or intramuscularly). Cefathiamidine is widely distributed in most bodily fluids and tissues; however, Cefathiamidine cannot pass through the blood-brain barrier. The protein-binding capacity of Cefathiamidine is 23%, and more than 90% of Cefathiamidine is excreted unchanged by the kidney^[1].