The antibiotic levofloxacin (Levaquin) has been approved by the Food and Drug Administration as a treatment for plague. Plague infections are rare in humans. There are three presentations of plague: bubonic (infected lymph nodes), pneumonic (infected lungs), and septicemic (infected blood). Bubonic or septicemic infection is usually transmitted from infected mammals, either through the bites of fleas or from direct contact with infected tissue or fluid from a sick or dead animal; pneumonic plague is transferred through respiratory droplets emitted by infected cats or humans.

According to the Centers for Disease Control and Prevention (CDC), the mortality rate from plague is high: 50% to 90% when left untreated and 15% when treated. Because of its lethality, Yersinia pestis, the bacterium that causes plague, is considered a potential bioterrorism agent, and effective treatment against plague is therefore important. The approval of levofloxacin for plague was based on animal studies with African green monkeys. Infected monkeys had a 94% survival rate when levofloxacin was used as treatment. Levofloxacin joins streptomycin, doxycycline, tetracycline, and other tetracyclines as antibiotics approved for the treatment of plague.

Levofloxacin is a fluoroquinolone antibiotic. It was previously approved to treat a variety of infections, such as pneumonias and other respiratory infections; skin, prostate, urinary, and kidney infections; and anthrax (as post-exposure prophylaxis). Like other fluoroquinolones, it has the potential to cause tendinitis or tendon rupture.

For more information on plague from the CDC, go to http://www.cdc.gov/plague.