Background:

IC50: 0.002 μg/ml for Streptococcus pneumoniae serotype 4

Penicillin G sodium is a penicillin antibiotic against sensitive organisms during the stage of active multiplication and acts by inhibiting the biosynthesis of bacterial cell wall mucopeptides. It is not active against penicillinase-producing bacteria, which include many strains of staphylococci.

In vitro: Penicillin G sodium works by interfering with the formation of the bacteria's cell wall. This weakens the cell wall and kills the bacteria. Penicillin G is highly effective in-vitro against staphylococci, streptococci and pneumococci. Other organisms sensitive in-vitro to penicillin G are Neisseria gonorrhoeae, Bacillus anthracis, Corynebacterium diphtheriae, Clostridia et al. Treponema pallidum is extremely sensitive [1].

In vivo: With intermittent intramuscular administration of penicillin normal rats were cured after doses of 4 mg/kg/d, whereas decomplemented rats recovered only after daily doses of above 100 mg/kg. When penicillin was administered by way of continuous infusion, doses of 3.5 mg/kg/d were required for a cure of infections in both normal and decomplemented rats [2].

Clinical trials: Penicillin G sodium is used to treat a wide variety of bacterial infections. It is also used to prevent the heart infection in patients with certain heart diseases who are having surgery. Penicillin G sodium is known as a natural penicillin antibiotic. It works by stopping the growth of bacteria [1].

Reference:
[1] Bakker-Woudenberg IA, van den Berg JC, Fontijne P, Michel MF.   Efficacy of continuous versus intermittent administration of penicillin G in Streptococcus pneumoniae pneumonia in normal and immunodeficient rats. Eur J Clin Microbiol. 1984 Apr;3(2):131-5.