Dr. Bao noted that an agent that could prevent or treat hearing loss of this type would have tremendous benefit because so many people are exposed to loud noises in their workplace setting. However, although these two agents were effective in mice, the study’s findings really set the stage for further drug discovery, he stressed.
Explore This IssueAugust 2007
“These agents are no longer used in the treatment of epilepsy,” he said. “They’re older and are associated with significant adverse effects, such as sedation and dizziness.” Therefore, the quest may now focus on finding drugs with similar calcium channel blocking properties, but with fewer adverse effects, he said. “We want to find drugs with a similar mechanism of action, perhaps other antiepileptic drugs, but with more favorable adverse effect profiles, to see if they are effective against noise-induced hearing loss.”
“The value of studies like this is that they use agents that are already approved by the FDA for another indication,” said Charles Syms III, MD, Clinical Professor of Otology and Neurotology at the University of Texas at San Antonio, where he is also the president of Ear Medical Group. “Therefore, if they have promise for another indication, the clinical trial process could be simplified.”
Earplugs Not an Option in Combat
Dr. Syms agreed with Dr. Bao that there is a high demand for agents that can prevent and treat noise-induced hearing loss. “For soldiers in combat settings, using earplugs is not an option, unlike civilian settings, such as people who operate heavy machinery,” he said. “Soldiers need to be able to hear commands and otherwise respond quickly to the combat environment.”
The findings are sufficiently encouraging that investigators should continue searching for an appropriate therapy for noise-induced hearing loss, Dr. Syms said. “If the side effects can be moderated, such as with a lower dose or a more refined agent, it would be reasonable to conduct clinical trials and to put the research on the ‘fast track’ for this indication,” he said.
Dr. Syms also encouraged the research into other T-type calcium channel blockers. “We know that these two drugs work in an animal model, but we don’t know the exact mechanism,” he said. “Therefore, it would be reasonable to pursue other drugs in this class.” However, he cautioned that just because some drugs within a class have a given effect, it does not mean that all such drugs would.