thedrifter
07-17-08, 06:29 AM
Drug may reduce combat-related hearing loss
By BRIAN KIMBALL
The Oklahoman
Article Last Updated: 07/17/2008 01:42:43 AM PDT
OKLAHOMA CITY — Two Oklahoma City scientists believe they are on a track that will lead to a significant reduction in combat-related hearing loss suffered by troops.
The scientists expect their discoveries to also help factory workers, machinists and others who deal with excessive amounts of loud noise on a regular basis, said Robert Floyd of the Oklahoma Medical Research Foundation.
Dr. Richard Kopke of the Hough Ear Institute and Floyd are developing a drug that reduces hearing loss after exposure to traumatic noise.
Hearing loss is the third-most-common disability among military veterans, behind mental disorders and musculoskeletal disorders such as back pain, according to the Institute of Medicine.
"It's a good thing if we can help some of these soldiers," Kopke said. "They're pretty young to be starting out" with significant hearing loss.
Kopke, a retired Army ear surgeon, conducted a clinical trial on 566 Marines in San Diego in 2003, using a drug better known for treating Tylenol overdoses.
He found that troops who received the drug — n-acetyl-cysteine, or NAC — dissolved in a beverage before going to the firing range retained 25 percent to 27 percent more hearing than the placebo group.
Now Kopke is teaming with Floyd to combine NAC with a drug used in cancer research and age-related diseases to create a mixture that prevents hair cells in the ear from dying after exposure to loud noises.
Their study focuses on administering the two-drug combination of NAC and 4-OHPBN nitrone after a traumatic noise event because "it may not be advantageous to give it to 1,000 people when only maybe 100 are going to experience hearing loss," Kopke said.
Floyd and Kopke are conducting trials of the drug on chinchillas, an animal that has a hearing range and ear structure similar to humans. The findings have yielded results better than expected, Floyd said.
After exposing the chinchillas to 105-decibel noise for six hours — roughly the equivalent of being in the front row at a rock concert — the animals are injected with the drug under their skin.
Without the medication, hair cells in the ear died, resulting in hearing loss.
The scientists have seen a retention rate of 90 percent of the animals' hearing for those that received the drug four hours after traumatic noise exposure.
Animals given the drug 12 hours after noise exposure retained 80 percent of their hearing. If given the drug 24 hours later, they showed a 50 percent retention rate, Kopke said.
The chinchillas' hearing levels are measured by putting a sensor in their ears that picks up electrical activity in their brains.
Floyd and Kopke also are checking for adverse effects the drug might have.
While NAC and the nitrone by themselves have been deemed safe by the FDA, it is unclear whether they are completely safe together.
The side effects discovered from Kopke's earlier trial on Marines using only NAC were minimal (headaches and upset stomach), he said.
The scientists hope clinical trials on humans are a possibility in one or two years, Kopke said.
Ellie
By BRIAN KIMBALL
The Oklahoman
Article Last Updated: 07/17/2008 01:42:43 AM PDT
OKLAHOMA CITY — Two Oklahoma City scientists believe they are on a track that will lead to a significant reduction in combat-related hearing loss suffered by troops.
The scientists expect their discoveries to also help factory workers, machinists and others who deal with excessive amounts of loud noise on a regular basis, said Robert Floyd of the Oklahoma Medical Research Foundation.
Dr. Richard Kopke of the Hough Ear Institute and Floyd are developing a drug that reduces hearing loss after exposure to traumatic noise.
Hearing loss is the third-most-common disability among military veterans, behind mental disorders and musculoskeletal disorders such as back pain, according to the Institute of Medicine.
"It's a good thing if we can help some of these soldiers," Kopke said. "They're pretty young to be starting out" with significant hearing loss.
Kopke, a retired Army ear surgeon, conducted a clinical trial on 566 Marines in San Diego in 2003, using a drug better known for treating Tylenol overdoses.
He found that troops who received the drug — n-acetyl-cysteine, or NAC — dissolved in a beverage before going to the firing range retained 25 percent to 27 percent more hearing than the placebo group.
Now Kopke is teaming with Floyd to combine NAC with a drug used in cancer research and age-related diseases to create a mixture that prevents hair cells in the ear from dying after exposure to loud noises.
Their study focuses on administering the two-drug combination of NAC and 4-OHPBN nitrone after a traumatic noise event because "it may not be advantageous to give it to 1,000 people when only maybe 100 are going to experience hearing loss," Kopke said.
Floyd and Kopke are conducting trials of the drug on chinchillas, an animal that has a hearing range and ear structure similar to humans. The findings have yielded results better than expected, Floyd said.
After exposing the chinchillas to 105-decibel noise for six hours — roughly the equivalent of being in the front row at a rock concert — the animals are injected with the drug under their skin.
Without the medication, hair cells in the ear died, resulting in hearing loss.
The scientists have seen a retention rate of 90 percent of the animals' hearing for those that received the drug four hours after traumatic noise exposure.
Animals given the drug 12 hours after noise exposure retained 80 percent of their hearing. If given the drug 24 hours later, they showed a 50 percent retention rate, Kopke said.
The chinchillas' hearing levels are measured by putting a sensor in their ears that picks up electrical activity in their brains.
Floyd and Kopke also are checking for adverse effects the drug might have.
While NAC and the nitrone by themselves have been deemed safe by the FDA, it is unclear whether they are completely safe together.
The side effects discovered from Kopke's earlier trial on Marines using only NAC were minimal (headaches and upset stomach), he said.
The scientists hope clinical trials on humans are a possibility in one or two years, Kopke said.
Ellie