Valnemulin

Valnemulin is a pleuromutilin antibiotic used in veterinary medicine. It is a semisynthetic derivative of tiamulin and is employed mainly in pigs to treat enteric infections, including swine dysentery caused by Brachyspira species, as well as other bowel diseases of commercial importance. It is also used in some cases for poultry under veterinary guidance.

The mechanism of action involves inhibition of bacterial protein synthesis. Valnemulin binds to the 50S ribosomal subunit, interfering with peptide bond formation and thus limiting bacterial growth. Its antimicrobial spectrum is strongest against Gram-positive bacteria and certain intracellular pathogens such as Mycoplasma, with notable activity against Brachyspira hyodysenteriae. Activity against many Gram-negative bacteria is limited, which influences its clinical use.

Administration and pharmacokinetics vary by species and formulation, but valnemulin is typically given orally. It is absorbed from the gastrointestinal tract, distributed to tissues, metabolized in the liver, and excreted in bile and urine. Pharmacokinetic properties, including absorption and elimination, depend on species, dose, and formulation.

Safety and resistance considerations are important. When used as directed, valnemulin is generally well tolerated in target animals, though adverse effects can occur rarely. Resistance can arise through mutations in ribosomal target sites, leading to cross-resistance within the pleuromutilin class. Because valnemulin is used in food-producing animals, withdrawal times are observed to ensure absence of residues in meat or other products.

Regulatory status varies by country, but valnemulin is approved for veterinary use in pigs (and, in some jurisdictions, poultry) with label-recommended dosing and withdrawal guidelines. It is not approved for human use.