In an effort to provide Alzheimer's and schizophrenia patients with better, safer medicines, biotech and big pharma have embarked on drug discovery programs targeting multiple cognitive mechanisms. Several of the resulting medications have progressed to late-stage clinical development. For patients suffering from these diseases, the new drugs have the potential to improve cognitive function over a longer term than available treatments, which fade in effectiveness over time.

Given the leaky and lucrative electronic trade in prescription drugs, it's likely that these medicines will be available to healthy people who hope to benefit from them as well.

Who might use them? Students will be tempted, as might players of any game involving counting or remembering (chess, bridge, and even poker and blackjack). Certain professionals might desire a boost in attention or memory: think of interns and residents, or airline pilots. Even the U.S. Department of Defense might be interested in improving the alertness of troops during battle.

But these potentially powerful medicines should not be made available to everyone, for two reasons. The first is safety. The last several years have provided many examples of side effects, some life-threatening, that emerged only after many thousands of patients had taken a drug (notably the painkiller Vioxx). The risks of harm far outweigh the benefits of modestly augmenting cognitive function in otherwise healthy people.

The second reason is that we still know relatively little about learning and memory and how they are integrated to make judgments and decisions. Drugs used to treat Parkinson's disease, which target a signaling chemical in the brain, have been linked in some cases to gambling and compulsive shopping. Many of those who might consider off-label use of these drugs must use swift judgments to make decisions that significantly affect the lives of others. While new medications might improve certain functions (attention, recall) measured on cognitive tests (see "Manipulating Memory," p. 54), it's unclear what effect this might have on decision making. I am certain that I would not want to be on a plane or in surgery the first time a pilot or surgeon has taken a cognitive enhancer.

Until we have a broad understanding of the safety of these compounds and deeper insight into how they might affect judgment and decision making, the FDA and other regulatory agencies should restrict the drugs to patients under medical supervision.

Michael K. Ahlijanian is vice president of ­research at EnVivo Pharmaceuticals.