ATCvet code:
QJ01AA06
Pharmacodynamics
Oxytetracycline is a bacteriostatic antibiotic that inhibits protein synthesis in susceptible bacteria. Inside the cell it binds irreversibly to receptors on the 30S subunit of the bacterial ribosome where it interferes with the binding of the aminoacyl-transfer RNA to the acceptor site on the messenger RNA ribosome complex. This effectively prevents the addition of amino acids to the elongating peptide chain, inhibiting protein synthesis.
Oxytetracycline had been shown to be active in vitro against the following bacterial species: Bordetella bronchiseptica, Trueperella pyogenes, Erysipelothrix rhusiopathiae, Escherichia coli, Mannheimia haemolytica, Pasteurella multocida, Staphylococcus aureus, Streptococcus agalactiae, and Streptococcus uberis.
Multiple genes have been identified which mediate resistance to tetracyclines and these genes may be carried on plasmids or transposons between both pathogenic and non-pathogenic bacteria. The most common mechanisms of resistance involve either the removal of the antibiotic from the organism by energy dependent efflux pumps or protection of the ribosome from binding by altered target sites. Resistance to one tetracycline confers cross-resistance across the whole group.
Oxytetracycline resistance has been identified in many veterinary pathogens; however, the prevalence of resistance varies widely between different locations. For veterinary isolates, the susceptible breakpoint is ≤ 2 µg/mL for bovine respiratory pathogens and ≤ 0.5 µg/mL for swine pathogens. For other isolates, the breakpoint for sensitive organisms in humans is used, which is ≤ 4 µg/mL for all organisms, except streptococci, which is ≤ 2 µg/mL (CLSI, 2007).
Pharmacokinetics
Maximum blood levels are achieved between 4 and 8 hours following intramuscular administration.