Pharmacotherapeutic group: Antibiotic
ATC Vet Code: QJ01CE09
Pharmacodynamic properties
Penicillin G is a beta-lactam antibiotic and its structure contains the beta-lactam ring and thiazolidine ring common to all penicillins.
Penicillin G shows excellent activity against susceptible Gram-positive bacteria such as Streptococci, Corynebacterium, Erysipelothrix and Clostridia but has limited activity against Gram-negative bacteria with the exception of the more fastidious Gram-negative aerobes such as Pasteurella spp.
Beta-lactam antibiotics prevent the bacterial cell wall from forming by interfering with the final stage of peptidoglycan synthesis. They inhibit the activity of transpeptidase enzymes, which catalyse cross-linkage of the glycopeptide polymer units that form the cell wall. They exert a bactericidal action but cause lysis only of growing cells.
Pharmacokinetic properties
After injection of Ultrapen LA, the procaine penicillin is rapidly absorbed from the site of injection with maximum penicillin levels of approximately 3.9μg/ml obtained in under 4.5 hours of subcutaneous injection in cattle, 1.3μg/ml obtained in under 4 hours of intramuscular injection in cattle and 2.1 μg/ml obtained in under 3 hours of intramuscular injection in pigs.
The penicillin elimination half-lives are approximately 16 hours for cattle and 7.5 hours for pigs following intramuscular injection and 8.5 hours for cattle following subcutaneous injection.