Valnemulin hydrochloride (Valnemulin HCl) is a broad-spectrum bacteriostatic agent inhibiting protein synthesis in bacteria by binding to the peptidyl transferase component of the 50S subunit of ribosomes.

Valnemulin (20 μM) completely inhibits the peptidyl transferase reaction, thus inhibits peptide bond formation. Valnemulin enhances the reactivity of nucleotides A2058 and A2059 moderately, whereas they protect U2506 strongly. [1] Valnemulin shows exceptional activity against M hyopneumoniae (MIC90 0.5 μg/mL) and M hyosynoviae (MIC range 0.1-0.25 0.5 μg/mL) field strains. [2] Valnemulin is mainly active against Gram-positive bacteria with moderate activity against some fastidious Gram-negative bacilli (e.g., anaerobic bacteria) and Mycoplasma and is used almost exclusively in animals, largely in swine in China. [3]

Valnemulin is absorbed rapidly, distributed widely and rapidly and excreted rapidly after oral administration to rats. [3] Valnemulin results in a rapid diminution of clinical signs, restoration of appetite and reversal of weight loss in young calves. Valnemulin results in a more rapid reduction of clinical scores and eliminated M. bovis from the lungs more effectively than Enrofloxacin. [4] Valnemulin significantly decreases the wet-to-dry weight (W/D) ratios of lungs, protein concentrations, and the number of total cells, neutrophils, macrophages, and leukomonocytes, and histologic analysis indicates that valnemulin significantly attenuates tissue injury. Valnemulin significantly increases LPS-induced SOD activity in BALF and decreases lung myeloperoxidase (MPO) activity activity as well. Valnemulin also inhibits the production of tumor necrosis factor-alpha, interleukin-6, and interleukin-1beta, which is consistent with mRNA expression in lung. [5]