Scientists have renewed the controversy over the bounds to which psychiatric drugs should be allowed to go, with research into a drug designed to erase unpleasant memories.

"Removing bad memories is not like removing a wart or a mole," said medical ethics lecturer Daniel Sokol of St. George's, University of London. "It will change our personal identity, since who we are is linked to our memories. It may perhaps be beneficial in some cases, but before eradicating memories, we must reflect on the knock-on effects that this will have on individuals, society and our sense of humanity."

Researchers have said that the new drug could help in the treatment of phobias, post-traumatic stress disorder or other memory-related psychological distress.

The drugs in question are actually simple beta-blockers, commonly used in the treatment of heart disease. Researchers from Amsterdam University recently tested the drugs by first inducing a spider-related anxiety in 60 men and women -- exposing them to electric shocks while showing them pictures of spiders and encouraging them to "actively remember" the pictures. The next day, half the participants were given a beta-blocker. All were then shown pictures of spiders again, while the researchers played a sudden noise.

The researchers found that participants on beta-blockers showed less fearful reactions -- measured by blinking rates -- than those given a placebo. This effect persisted the next day, even without a reuse of the drugs.

The researchers hypothesize that this occurs because the beta-blockers interfered with the recreation of the original fearful memory, but some are skeptical.

"All they've shown so far is that the increased ability to startle someone if they are feeling a bit anxious is reduced," said Neil Burgess of the Institute of Cognitive Neuroscience.

But the very prospect of such a drug has raised concern among bioethics experts. Potential complications might include people interfering with the criminal justice process either accidentally or deliberately by erasing their own memories, while side-effects might include the erasure of positive memories or disruption of the learning process.