For potential side-effects include heart attacks, blurred vision, pain, numbness and seizures.
Drugs meant for treatment of dementia or Attention Deficit Hyperactivity Disorder (ADHD) generally work by increasing levels of certain brain chemicals.
This helps hyperactive children to focus on one thing at a time - but when used in otherwise healthy adults, it makes them feel more alert and full of energy.
Only last summer there were reports that British parents were buying Ritalin on the internet for their healthy children to boost exam results. As many as 10 per cent of students at American universities are thought to be using Ritalin and Adderall (another ADHD drug) to improve their performance, reports The Daily Mail from the UK.
And it's not just students who are getting chemical help. Another prescription drug, Provigil, is widely used by businessmen and other professionals to overcome the effects of jet-lag by making them feel focused and alert even when they haven't slept. Users also report their performance improves as well. The drug is officially licensed to treat narcolepsy,a neurological condition most characterized by Excessive Daytime Sleepiness (EDS).
psychology professor wrote an article in the science journal Nature, calling for a debate on the use of these 'cognitive-enhancing' drugs. 'We've done informal research that shows not only students, but also senior academics, are using smart drugs to improve their performance,' says the author and professor of clinical neuropsychology, Barbara Sahakian.
'I was offered Provigil by a colleague to help me give a presentation after an eight-hour flight, and some of my fellow academics use it regularly.' She believes that as both education and business become more competitive, demand for these drugs will increase, fuelled by easy availability over the internet. A pack of Provigil can be bought online for £64.
'As a society, we need to have a debate about how we want to control the use of these drugs,' says Prof Sahakian. 'Do we want to accept them and have them handed out at the university pharmacy, or are they a form of cheating? Should there be random drug-testing of students before they sit exams?'
Concerns centre around both the potential side-effects of such drugs and their easy availability.
Of course drugs that fight off sleep have been in use for more than a century. The active ingredient in the present day Adderall and Ritalin is amphetamine - this was first manufactured in 1887and was used by soldiers to stay awake. Women have also long used it for dieting.
But then side-effect dangers are very real. Provigil, for instance, which is known to have the mildest side-effects, may result in headache, nausea, nervousness, rhinitis (inflammation of the nose lining), diarrhoea and back pain.
What's more, there is some evidence that Ritalin may affect the development of young brains. (A more positive, if bizarre side-effect is that the concentrated attention produced by Adderall and Ritalin has been turned to housework; universities in the American report that students' apartments have never been cleaner.)
However, enthusiasts claim that these drugs are just the beginning. They are the pharmaceutical equivalent of the Wright brothers' bi-plane, forerunner of today's supersonic jets. The era of 'cosmetic pharmaco-neurology' is on its way, when our growing knowledge of genetics and biochemistry will allow scientists to sculpt all sorts of human behaviours, from faithfulness in marriage to emotional stability, with greater safety than current smart drugs.
Much hope is being put in a new class of drug called ampakines, which seem to be able to improve alertness without the jitteriness that comes with caffeine or drugs such as Adderall.
A study of one of these compounds - known as CX717 - was done two years ago at the University of Surrey. When it was given to 16 healthy young men who'd been deprived of sleep, it improved their memory, attention, alertness and problem-solving ability.
Ampakines boost the amount of a brain chemical - glutamate - which is involved in creating memories. 'We all have the same computer,' says Gary Lynch, a neuroscientist at the University of California Irvine, who invented the drugs. "But some of us are running with different voltage levels. Ampakines boost the voltage."
He believes that if his drugs prove to be safe, the social implications could be astounding. "At the moment, people accept their place in the intellectual hierarchy," he says. "What happens when it becomes possible for them to change?"
But there are warning signals from the animal world that indicate some of the things that could go wrong.
Mice whose brains have been boosted with smart drugs are certainly better learners, but some are also more sensitive to pain. Higher doses of ampakines are more effective at strengthening memories, but in one set of studies, the animals on high doses were also more likely to suffer from seizures.
Then there is the issue of giving drugs to people who are otherwise healthy. Another scientist researching the pharmaceutical holy grail of a safe and effective memory-booster is Nobel Prize-winner Professor Eric Kandel of Columbia.
His work on sea slugs found that a protein called CREB was crucial for memory formation, and he's now involved in trials of a series of CREB-boosting drugs to help people with the memory loss caused by disorders such as dementia and Parkinson's disease.
He is horrified by the idea that such drugs should be used by healthy students to boost exam scores. "It's awful," he said. "They are designed for people with serious problems who really need help. The idea that character and intelligence is to be judged by a small improvement in an exam result is absurd."
Cephalon, which makes Provigil, declined to comment directly on its widespread unapproved use. A spokesperson said: "Our company is exclusively engaged in activities which relate, in compliance with the rules and regulations of the pharmaceutical industry, to the officially approved indications which are excessive daytime sleepiness, mainly narcolepsy."
The authorities, meanwhile, are unable to address this issue. The UK drugs watchdog, the Medicines and Healthcare Products Regulatory Agency, only licenses drugs to treat medical conditions.
It also has no control over drugs bought through the internet but advises against it. "If people self-prescribe in this way they could damage their health," said a spokesperson.