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April 1, 2008
Penicillin’s Back: FDA Raises Breakpoints for S. pneumoniae Pneumonia

Penicillin, one of the safest and most effective drugs for the treatment of community-acquired pneumonia caused by Streptococcus pneumoniae, is back in the armamentarium following action by the Food and Drug Administration (FDA) and pressure from IDSA and several key members.

FDA has raised the concentration at which S. pneumoniae is considered susceptible to penicillin, according to an amended package insert for Baxter Healthcare Corporation’s penicillin G approved by FDA and obtained by IDSA. The breakpoint changes are:




Minimum Inhibitory Concentration (MIC) (mcg/mL)


Susceptible (S)

Intermediate (I)

Resistant (R)









The susceptible breakpoint for meningitis caused by S. pneumoniae remains unchanged (0.06 mcg/mL). The package insert is available online from FDA’s website.

Evidence has been mounting for years that penicillin is effective against pneumococcal pneumonia at concentrations that would fail for meningitis or otitis media. Victor L. Yu, MD, FIDSA, co-authored one significant study in Clinical Infectious Diseases in 2003 looking at patients with pneumococcal bacteremia who were initially treated with penicillin before laboratory tests came back resistant. “It turned out they uniformly did fine,” Dr. Yu said. The study won IDSA’s Emmanuel Wolinsky Award in 2003. Since then, several other studies have been published showing penicillin is effective against pneumococcal pneumonia at concentrations that would fail for other diseases.

IDSA strongly supported legislation passed last fall that requires FDA to update antimicrobial breakpoints. The Clinical and Laboratory Standards Institute (CLSI) adopted the revised breakpoints in June 2007 and published them in January 2008.  CLSI also supported a citizens’ petition written by Dr. Yu and others urging FDA to raise the penicillin breakpoints by submitting two “citizens petitions” of its own. Dr. Yu learned this month that FDA had signed an approval letter for Baxter’s amended package insert on March 1. “This was a case where FDA acted expeditiously,” Dr. Yu said.

Although a formal response from the FDA to Dr. Yu’s group and CLSI has not yet been received and the package inserts of other generic penicillins have not yet been changed, “the implication of the FDA’s action is that all of the package inserts for generic penicillins should be changed and that microbiology laboratories and clinicians should feel comfortable using the revised breakpoints to guide therapy for pneumococcal infections,” said Melvin P. Weinstein, MD, FIDSA, IDSA’s liaison to CLSI.

This is good news, Dr. Yu said, because now that quinolones have become the standard therapy for community-acquired pneumonia, reports of quinolone failures are on the rise. “You use it and you lose it,” he said.

“People laughed at me when I said I would bring back penicillin,” Dr. Yu said. But, he added, it will take some time and some effort for penicillin to really make a comeback. As empiric therapy has taken over, he said, clinicians and laboratories have lost the skills and the tools to diagnose the causes of CAP. “If anyone should be delighted, it should be infectious diseases specialists, because the skill of making a diagnosis returns. But because the practice of giving empiric therapy without thinking has become so inculcated in the last seven years, I think it’s going to take publicity to go back to what we were so good at.”

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