Levofloxacin is a fluoroquinolone antibacterial. Like other fluoroquinolones, levofloxacin acts to inhibit DNA gyrase and cell DNA and RNA synthesis. It is the L-isomer (S-enantiomer) of ofloxacin and is more active in vitro against gram-positive bacteria and anaerobes than some other fluoroquinolones. Levofloxacin is a human-labeled antibiotic but has been used in veterinary medicine to treat various bacterial infections. Its spectrum of activity includes gram-negative bacilli of the Enterobacteriaceae and fluoroquinolone-susceptible Pseudomonas aeruginosa.
It also has activity against some gram-positive cocci, including Staphylococcus spp. Multi-drug– resistant bacteria, including gram-negative bacilli of the Enterobacteriaceae and methicillin-resistant strains of Staphylococcus, are likely to be resistant to levofloxacin and other fluoroquinolones. It also has activity against some anaerobic bacteria and other organisms (e.g., Chlamydia, Mycoplasma, and Mycobacterium spp.). In human medicine, it is considered one of the “respiratory fluoroquinolones” because of its broad-spectrum activity against gram-positive, gram-negative, and anaerobic bacteria.
Levofloxacin is available as inexpensive, generic tablets, which has facilitated its use in veterinary medicine. According to the manufacturer’s information for use of the drug in humans, the drug undergoes limited metabolism and is not metabolized by cytochrome P450 enzymes. It is almost entirely eliminated in the urine, and the pharmacokinetics are not affected by liver disease. The tablets can be taken with or without food.