University of Florida researchers have figured out a new way to test new hearing-loss prevention drugs in people that could put those medicines on the fast track to federal approval and widespread use.
The UF technique, detailed in the journal Ear & Hearing, uses music to safely induce low-level temporary hearing loss that allows scientists to track the effectiveness of drugs designed to prevent deafness. The method gets around the longstanding problem of how to safely create reversible deafness in people in order to see how well new drugs work.
"There's a real need for drug solutions to hearing loss," said lead investigator Colleen Le Prell, an associate professor in the department of speech, language, and hearing sciences at the UF College of Public Health and Health Professions.
"Right now the only options for protecting against noise-induced hearing loss are to turn down what you're listening to, walk away from it or wear ear plugs, and those options may not be practical for everyone, particularly for those in the military who need to be able to hear threats."
About 26 million American adults have noise-induced hearing loss, according to the National Institute on Deafness and Other Communication Disorders. Damage to hearing-related hair cells in the inner ear by loud noise is irreversible. Hearing aids can help amplify sound and implanted devices can improve hearing, but they do not restore normal hearing.
Some new drugs have been shown to prevent noise-induced hearing loss in laboratory animals, but have been impossible to test in humans because there is no safe, effective method for inducing deafness.
But the UF work could change that reality, and speed development of drugs to protect people at risk of hearing damage.
Le Prell’s technique uses controlled music levels to cause low-level, temporary hearing loss in human participants. To test the technique, she asked a group of study participants to listen to music on a digital music player via headphones for four hours at sound levels ranging from 93 decibels — equivalent to a lawn mower engine — to 102 decibels, the noise of a jackhammer. Each participant was given a hearing test four times, after the listening sessions, and follow-up tests one day and one week later.
The tests those who listened to the loudest music levels lost a small amount of hearing — six decibels, on average — 15 minutes after the music stopped, but hearing returned to normal within three hours.
The next step is to test the technique in two first-of-a-kind clinical trials of therapeutics designed to prevent noise-induced hearing loss. The first study uses a dietary supplement called Soundbites — manufactured by Hearing Health Science, a University of Michigan company — that beta carotene, vitamins C and E,and the mineral magnesium. This antioxidant formula, the patent for which Le Prell shares, has been shown to prevent hearing loss in laboratory animals.
A second study involves a drug called SPI-1005 produced by Sound Pharmaceuticals Inc. containing a molecule called ebselen that mimics a protective inner ear protein.
The U.S. Food and Drug Administration will monitor both studies.
"We really want to find out what's going to work and we want to make it possible for strategies that do work to get in the hands of the people who need them," Le Prell said.
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