Co-author Giacino said the researchers were surprised when they saw an immediate leveling off between the two groups in the final two weeks.
"But when I take a step back, it is even stronger evidence that this drug was doing something," he added.
Neurologist Dr. Daniel Labovitz, of Montefiore Medical Center in New York City, believes hope should remain in check despite the promising results. "It's not a home run. It's a small change and it was temporary, and I think that would be the message that has to come through."
Labovitz said the drug appears to be gently waking the patients. "If this trial holds up in larger, longer-term studies, maybe you can enhance the ability of [rehabilitation] therapists to interact with patients while they're on the drug."
Giacino said they researchers also aimed to look at side effects of amantadine.
"There was not a single category where the amantadine group had a higher rate of side effects than the placebo group," he said.
Whyte said that while this research may influence more rehabilitation experts to use amantadine for this type of patient, more challenges remain before the drug's impact is completely understood.
"This study isn't the end of the story," Whyte said.
For more on traumatic brain injury, head to the U.S. National Institute of Neurological Disorders and Stroke.
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