Scientists at a conference in Washington DC heard that the drug, containing chemicals known as ampakines, also improves recall in people as young as 20.
Dr Gary Lynch, a neuropharmacologist at the University of California at Irvine, said the drugs could one day be used by students cramming for exams. "We're going to need some kind of legislation on how we use these drugs," he told the Society for Neuroscience.
The findings have implications for those with Alzheimer's disease, which causes progressive dementia.
In the study, at the Karolinksa Institute in Stockholm, a dozen men aged between 65 and 73 who were taking the drug scored higher in memory tests than men taking a placebo. Medium doses of ampakines doubled their scores, according to a report in New Scientist, while higher doses trebled them, bringing the scores into the range seen for 20- to 25-year-olds. In younger people the effect was less dramatic but still detectable.
Ampakines are thought to improve the flow of information between cells.
Any therapeutic drug based on the chemical is some years away but American scientists plan to try it on Alzheimer's patients early next year.