(Rac)-Moxifloxacin ((Rac)-BAY 12-8039 free base) is an isomer of Moxifloxacin Hydrochloride. Moxifloxacin Hydrochloride (BAY 12-8039) is an orally effective 8-methoxyquinolone antibacterial agent used in studies on acute bacterial sinusitis, acute bacterial exacerbations of chronic bronchitis, and infectious pneumonia.

Moxifloxacin hydrochloride (BAY 12-8039) was evaluated for its in vitro activity against Listeria monocytogenes using a bone marrow-derived mouse macrophage model. Time-kill curves and intracellular growth inhibition assays compared it with amoxicillin. Moxifloxacin acted more rapidly, beginning its effect within the first 3 hours and achieving complete broth sterilization within 24 hours of incubation. It also seemed to protect macrophages from lysis, as many cells survived after 24 hours of incubation.

Moxifloxacin (BAY 12-8039; 12 mg/kg; intravenous injection; administered once to three times daily over 7 days; in male Wistar rats) extends survival when administered every 8 hours. Tissue cultures taken 30 hours after bacterial challenge reveal significantly reduced bacterial overgrowth in the spleen and lungs of moxifloxacin-treated animals compared to saline-treated ones, with no observed toxicity.