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Pharmacological particulars
Pharmacotherapeutic group: Antibacterials for systemic use, macrolides, tylosin. ATC vet code: QJ01FA90
Pharmacodynamic properties
Tylosin is a macrolide antibiotic and exerts its antibiotic activity by a similar mechanism to other macrolides i.e. binding to the 50S fraction of the ribosomes resulting in an inhibition of the synthesis of proteins. Tylosin has mainly a bacteriostatic activity.
Tylosin has an antibiotic effect against Gram positive cocci (Staphylococci, Streptococci), Gram positive bacilli (Erysipelothrix spp.), some Gram-negative bacilli (Pasteurella spp., Mannheimia spp.) and Mycoplasma spp.
Resistance to macrolides is usually plasmid-mediated but modification of ribosomes may occur through chromosomal mutation. Resistance can occur by i) decreased entry into bacteria (most common with the gram-negative bacteria), ii) synthesis of bacterial enzymes that hydrolyse the drug and, iii) modification of the target (the ribosome).
This latter resistance type may also lead to cross-resistance with other antibiotics that preferentially bind to bacterial ribosome. Gram-negative anaerobic bacteria are often resistant.
Resistance of Brachyspira hyodysenteriae to tylosin has been reported
Pharmacokinetic properties
Absorption: Following intramuscular injection, tylosin blood levels peak 1-2 hours post-injection. Duration of activity is approximately 12 hours.
Distribution, Biotransformation and Elimination: Tylosin levels of 1.4 to 1.6 and 2.2 to 6.7µg/ml were recorded in serum and lung tissue respectively following intramuscular injection of 8.8 mg/kg bodyweight in pigs. Measurable amounts of tylosin were still present in both serum and lung tissue at 12 hours post-injection. Tylosin concentrations were greater in lung tissue than serum at all sample times.