Students are increasingly using brain-boosting drugs – and they're virtually impossible to ban, an expert warned today.

Drugs normally used for conditions such as Alzheimer's disease and attention deficit hyperactivity disorder (ADHD) are being used by students around the world to improve their academic performance.

In some US universities, a quarter of students are reportedly using "smart drugs", and there is anecdotal evidence of increasing use on British campuses.

The Academy of Medical Sciences said last year that the use of medicines "off label" is likely to rise.

"The expectation that 'off-label' use will increase is borne out by existing advertising of cognition enhancers and smart drugs on the internet," it said. The use of the drugs in UK schools and workplaces raised "many of the same issues as the use of performance-enhancing drugs in sport".

Vince Cakic, from the department of psychology at the University of Sydney, writing in the Journal of Medical Ethics, said today that smart drugs, or "nootropics", were highly attractive to students and nearly impossible to ban.

"High school and university are the primary competitive spheres of many people's lives, and ones that have significant bearing upon their lives, in terms of both career opportunities and future earning capacity.

"The pressure to succeed academically is very real, and in a climate in which high-stakes public examinations have increased demand for private tuition, it is likely that all avenues for performance enhancement will be exhausted."

He said the failures and inconsistencies in the anti-drugs policy in sport could be mirrored when it comes to the use of smart drugs in the academic world.

"If the current situation in competitive sport is anything to go by, any attempt to prohibit the use of nootropics will probably be difficult or inordinately expensive to police effectively."

Cakic said that although smart drugs had been shown to improve brain power by only a modest amount, "it appears likely that more effective compounds will be developed in the future and that their off-label use will increase".

He said: "It is thought that future nootropics will encompass a wide array of drugs that enhance memory, attention, alertness, motivation, executive function, creativity or the need for sleep.

He added: "The possibility of purchasing 'smartness in a bottle' is likely to have broad appeal to students."

The drugs are available in the UK but are prescribed for a range of medical conditions. They include donepezil (Aricept), galantamine (Reminyl) and rivastigmine (Exelon) for use in Alzheimer's, methylphenidate (Ritalin) for use in ADHD, the stimulant modafinil for narcolepsy and the amphetamine Dexedrine.

A previous report has identified 27 major agents currently available in the UK that boost brain performance, including 10 dietary supplements and 17 pharmaceutical drugs.

Cakic said the argument that these drugs should be banned for non-medical use because they offer some students an unfair advantage is like suggesting private tuition be banned.

The drugs might even level the playing field for those who have been disadvantaged, he said.

A spokeswoman for Universities UK said: "Currently, much of the evidence available on the use of drugs such as Ritalin among students is largely anecdotal.

"However, universities take the issue of drug abuse very seriously, and would have grave concerns about students taking drugs not prescribed to them. Not only is this illegal but it also poses health risks to those students.

"All universities would advise students under pressure to seek advice from university counselling services, welfare officers or their GP."