Purifying Common Antibiotic May Lower Risk of Deafness

ear thermometer

WEDNESDAY, Dec. 23, 2020 (HealthDay News) -- Reformulation and improved purification of the popular antibiotic gentamicin would reduce the risk that it will cause deafness, researchers say.

U.S. hospitals use gentamicin to treat a variety of bacterial infections, and the drug is popular in developing countries because it's highly effective and cheap.

But up to 20% of patients treated with gentamicin suffer some degree of irreversible hearing loss.

Gentamicin belongs to a class of antibiotics called aminoglycosides that have been in use since the 1950s. Those used today are a mixture of five subtypes. The formula is allowed to contain up to 10% impurities.

In this study, the researchers analyzed the different subtypes and identified the one most toxic to ear tissue (sisomicin) and the least toxic one (C2b). Both are equally effective.

The researchers also found that removing impurities from the mixture also reduced toxicity to the ear, according to findings recently published in the journal Proceedings of the National Academy of Sciences.

"What this study shows is that the formulation that is currently in a hospital bottle of gentamicin is not optimized," said study senior co-author Anthony Ricci. He's a professor of otolaryngology at Stanford University in California.

All of the subtypes now used in gentamicin are required by both U.S. and international law.

"If we just use the subtype that's less toxic or change the formulation of this bottle, we can make the drug much less" toxic to the ear, Ricci said in a university news release.

Because all of the subtypes used in gentamicin are approved by the U.S. Food and Drug Administration, new formulations don't necessarily need to be retested in humans and could quickly be available for use, according to Ricci.

"We've developed a simple method of reformulating the drug that should be put to use as soon as possible," he said.

The researchers will recommend that the FDA change its requirements for how drug companies make gentamicin.

"Currently, the FDA's instructions for how to make aminoglycosides are making people go deaf," Ricci said.

He said the drugs are used because they save a lot of lives. "We've stopped paying attention to their toxic side effects because living with hearing loss is better than dying," Ricci added.

More information

The American Academy of Family Physicians has more on antibiotics.

SOURCE: Stanford University, news release, Dec. 17, 2020

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