Azithromycin side effects add to antibiotic woes

LONDON – Recent worries over antibiotics losing their effectiveness will only be exacerbated by the FDA’s latest drug safety update, released yesterday, which stated that the commonly prescribed antibiotic Azithromycin can cause abnormal changes in the electrical activity of the heart.

Azithromycin, currently marketed as Zithromax by Pfizer, is indicated for a large range of bacterial infections, such as chronic obstructive pulmonary disorder (COPD), acute bacterial sinusitis, nosocomial pneumonia, and certain skin structure infections. The drug’s wide-ranging use, improved safety profile, and short treatment duration of just five days, compared to the 10 days required by many competing antibiotics, have made Azithromycin a popular choice among physicians.

These detrimental effects were linked with potentially fatal heart arrhythmias in patients who already exhibited risk factors such as QT interval prolongation, low blood levels of potassium or magnesium, and slower heart rates. They were also indicated in patients currently being treated for heart arrhythmias with certain drugs. A study first published in the New England Journal of Medicine in May 2012 showed that patients treated with azithromycin displayed a higher likelihood of developing complications of the heart in comparison to patients treated with amoxicillin, ciprofloxacin, or levofloxacin, or left untreated. The updated safety information is likely to have been delayed by the manufacturers’ own studies to corroborate this evidence.

Dr. Brad Tebbets, GlobalData analyst covering Infectious Diseases, does not expect the FDA’s announcement to dramatically affect the sales of Zithromax, but states: “The news could decrease its uptake among patients at risk of cardiac complications, and these adverse events could also make Zithromax more susceptible to competition from novel antibiotics.”

Some pharmaceutical and biotech companies are attempting to address the rising demand for novel antibiotics, in a pharmaceutical field currently in a state of flux. “Most currently prescribed antibiotics are produced by generic manufacturers, and there is little incentive for pharmaceutical or biotech players to launch new products into the market,” says Dr. Ramya Kartikeyan, GlobalData’s senior analyst covering Infectious Diseases. “The GAIN Act in the US and the Innovative Medicines Initiative in the EU both reflect acknowledgement by governmental, regulatory and research bodies alike of the need to increase research efforts to develop cures against drug-resistant bacterial infections.” The UK’s chief medical officer, Sally Davies, recently stated that the antibiotics market has stagnated over the past 20 years.

However, a recent deal between Cubist Pharmaceuticals and Astellas showed Cubist putting up as much as US$25m for an antibiotic pipeline candidate, ceftolozane. Ceftolozane, in combination with tazobactam, has come out with impressive and encouraging results in later-stage trials. The drug combination is currently set to be used against the gram-negative bacteNike