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Pharmacological particulars
Pharmacotherapeutic group: antibacterial for systemic use
ATCvet code: QJ01XQ01
Pharmacodynamic properties
Tiamulin is a bacteriostatic semi-synthetic antibiotic belonging to the pleuromutilin group of antibiotics and acts at the ribosomal level to inhibit bacterial protein synthesis.
Tiamulin has shown a in-vitro activity against a wide range of bacteria such as Brachyspira hyodysenteriae, Brachyspira pilosicoli, Lawsonia intracellularis and Mycoplasma spp.
Tiamulin is bacteriostatic at therapeutic concentrations and has been shown to act at the 70S ribosome level and the primary binding site is on the 50S subunit and possibly a secondary site where the 50S and 30S subunits join. It appears to inhibit microbial protein production by producing biochemical inactive initiation complexes, which prevent elongation of the polypeptide chain.
Mechanisms responsible for resistance development in Brachyspira spp to the pleuromutilin class of antibiotics are considered to be based on mutations at the ribosomal target site. Clinically relevant resistance to tiamulin requires combinations of mutations around the tiamulin binding site.
Resistance to tiamulin may be associated with decreased susceptibility to other pleuromutilins.
Pharmacokinetic particulars
Tiamulin is well absorbed in the pig (over 90%) following oral administration and widely distributed through the body. Following a single oral dose of 10 mg and 25 mg tiamulin/kg bodyweight, the Cmax was 1.03 µg/ml and 1.82 µg/ml respectively by microbiological assay and the Tmax was 2 hours for both. Tiamulin has been shown to concentrate in the lung, a target tissue, and also in liver, where it is metabolised and excreted (70-85%) in the bile, the remainder is excreted via the kidney (15-30%). Tiamulin which has not been absorbed or metabolised, passes down the intestines to the colon and concentrates there.
Tiamulin is well absorbed in chickens (70-95%) after oral administration.
Tiamulin distributes widely through the body and has been shown to concentrate in the liver and kidney (sites of excretion) and in the lung (30 times serum level). Excretion is mainly via the bile (55-65%) and kidney (15-30%) as mainly microbiologically inactive metabolites and is quite rapid, 99% of the dose within 48 hours.
In turkeys serum levels of tiamulin are similar to chickens. In breeders on 0.025% tiamulin the average serum level was 0.36 µg/ml (range 0.22-0.5 µg/ml).
There are no pharmacokinetic data available for rabbits.