Aspirin limits drug-caused deafness.

If a finding in guinea pigs holds true in people, regular aspirin may prevent the hearing loss sometimes caused by certain antibiotics. Aminoglycosides such as streptomycin, gentamicin, and neomycin are widely used against infections in developing countries because of their low cost. In developed countries, physicians use these drugs to treat tuberculosis and infections resistant to other antibiotics.

When aminoglycosides bind iron, they produce free radicals, unstable molecules that can damage or kill cells. Hair cells in the inner ear--which don't regenerate and are crucial for hearing--are especially sensitive. Even in countries where physicians carefully monitor the drug's side effects, one in five people given aminoglycosides loses some hearing.

Aspirin's benefit stems from the fact that it quickly breaks down into salicylate, a compound that soaks up extra iron and thereby prevents aminoglycosides from forming free radicals, says Jochen Schacht of the University of Michigan in Ann Arbor.

Six animals given both gentamicin and aspirin had less hair-cell damage and hearing loss of less than 20 decibels, he reports in the July LABORATORY INVESTIGATION. Another six guinea pigs given gentamicin injections alone lost many hair cells and experienced as much as 70 decibels of hearing loss.

"Salicylate levels providing protection in guinea pigs fall into the lower range recommended for anti-inflammatory therapy in humans," he says. He's currently testing the effects of aspirin therapy among people taking aminoglycosides in China.