Chapter 9 – Pleuromutilins

Overview/Relevance

Pleuromutilins are similar to macrolides and lincosamides in their mode of action. In swine, the most commonly used pleuromutilin is tiamulin, used in the control of enteric disorders such as swine dysentery and respiratory issues, especially the ones involving Mycoplasma hyopneumoniae. It has a synergistic effect with tetracyclines.

Useful molecule to know in swine medicine

• Tiamulin

Mechanism of Action

Pleuromutilins bind to the 50S subunit of the ribosome and stop the addition of new amino-acids, inhibiting protein synthesis.

Check your learning: Pleuromutilins and Mechanism of Action

Spectrum

Pleuromutilins are extremely effective against anaerobic bacteria and Mycoplasma spp. However, their activity against aerobic Gram + and Gram – is limited.

Absorption

Overall, pharmacokinetic properties of pleuromutilins are still relatively unknown due to their recent discovery. Tiamulin is a lipid soluble and basic molecule that is easily absorbed in the intestinal tract, giving it a good bioavailability. It also tends to concentrate in the milk. When given as medicated feed instead of by itself orally, the bioavailability of tiamulin tends to decrease dramatically in swine.

Distribution

Tiamulin has a good Volume distribution and penetrates tissue effectively. Concentration of the molecules in the colon is several fold the one found in the plasma making them drugs of choice for the treatment of swine dysentery. Tiamulin strongly inhibits the activity of P450 cytochromes in the liver. P450 cytochromes are involved in phase I metabolism of numerous antimicrobials.

Elimination

Elimination of tiamulin is through the bile more than through the urine.

Adverse effects

An older study suggests that metabolites of tiamulin in urine could irritate the perineal skin; this finding was potentiated by higher pig density and lower hygiene.

Tiamulin should not be used with ionophores.