Levofloxacin Approved for Treatment of Plague

Emma Hitt, PhD

May 01, 2012

May 1, 2012 — The fluoroquinolone antibiotic levofloxacin (Levaquin, Janssen Pharmaceuticals Inc) has been approved as part of a US Food and Drug Administration (FDA) priority review application for the treatment of plague.

The agency has also approved levofloxacin as a preventative agent for reducing the risk of getting plague after exposure to Yersinia pestis, the infectious agent that causes plague.

The new approval adds to the current treatment options for plague, which include streptomycin, doxycycline, and tetracycline.

According to the written release issued by the FDA last week, plague is extremely rare, with only 1000 to 2000 cases worldwide each year. The 3 most common forms infect the lymph nodes (bubonic), lungs (pneumonic), and bloodstream (septicemic).

Plague is transmitted to humans through bites from infected fleas, contact with infected animals or humans, or laboratory exposure. Yersinia pestis also is considered a bioterrorist threat agent.

Given that plague is so rare in humans, the new approval for levofloxacin was issued under the agency's Animal Efficacy Rule, which allows efficacy findings from certain animal studies to be used in cases where it is not feasible or ethical to conduct trials in humans.

The current approval was based on findings from an efficacy study conducted in 24 African green monkeys that were infected with the plague bacterium in a laboratory setting.

Animals were randomly assigned to receive 10 days of levofloxacin or placebo within 6 hours of the onset of fever after being infected. Of 17 monkeys that received levofloxacin, nearly all (94%) survived, whereas all 7 monkeys treated with placebo died.

"Today's approval broadens the available therapeutic treatments for plague," noted Edward Cox, MD, MPH, director of the Office of Antimicrobial Products in FDA's Center for Drug Evaluation and Research.

"It also further demonstrates the usefulness of animal model studies to collect needed efficacy data in cases where human trials are not ethical or feasible."

Common side effects reported in previous human clinical trials of levofloxacin for other indications were nausea, headache, diarrhea, insomnia, constipation, and dizziness (all reported at an incidence of > 3%).

Serious but rare side effects known to be associated with levofloxacin include tendinitis and tendon rupture, worsening of muscle weakness in people with the neuromuscular disorder myasthenia gravis, allergic reactions, liver damage, abnormalities of the blood, effects on the nervous system, and abnormal heart rhythm.

"However, given that plague is a very serious and often deadly condition, the benefit of Levaquin for treating plague outweighs these potential risks," the FDA notes.


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