websites offering so-called digital drugs which claim to replicate the effects of alcohol, marijuana, cocaine and heroin have prompted concerns that they could act as 'gateways' for people to use real versions of the drugs.

Videos of individual users apparently suffering severe reactions after listening to atonal tracks known as 'I-Doses' are currently available on YouTube, while drug authorities in the US state of Oklahoma recently wrote to parents advising them of concerns about their use.

The 'drugs' claim to use a form of therapy known as 'binaural beats', which can alter the moods and behaviour of some users.

Typically, this is done in a therapeutic setting to treat a range of symptoms such as anxiety, chronic pain, depression and other clinical issues, although some people are not susceptible to this approach.

But at least one website, I-Doser.com is currently selling 'doses' of a wide range of drugs for download onto users' iPods, mp3 players or personal computers, or via CD.

Typical prices for the drugs are $3 (€2.30) per dose, while customers can also buy "bundles" of doses at reduced rates.

Among the broad categories of drugs listed by the website are diet, recreational, hallucinogenic, prescription, sexual, quick hits and anti-anxiety.

It then goes on to offer others with titles such as alcohol, acid, rave, crystal meth, crack, cocaine, GHB, hash and heroin.

Last week, the website listed peyote, [mescaline], marijuana, ecstasy, Trip, LSD and MultipleO among its top 10 bestsellers.

Other I-Dose enthusiasts have also posted free versions of the doses on various online discussion boards and websites.

Dr Joseph Keaney of the Institute of Clinical Hypnotherapy & Psychotherapy in Cork told the Sunday Tribune he was shocked at the types of 'drugs' being offered online. He warned that using such I-Doses could reinforce an individual's addiction.

"In my opinion, they would have to have had experience of the real drug to get any effect. If they have used heroin or hash previously, their expectation would be that they would recreate those experiences," he said.

"In relation to the drugs issue, it is totally unethical to provide these in this way. It is reinforcing someone's addiction, and could cause them to want to take more of the real drug.

"In my view it does work, but only on people who have experienced the drug previously."

A spokesman for Oklahoma's Bureau of Narcotics and Dangerous Drugs recently told a local news outlet there that it feared children could be encouraged to experiment with real drugs after taking an I-Dose.

This had prompted the authorities to write to parents at one school, warning them about the new trend.

However, other US-based experts argue that there is no risk from the use of binaural beats, with users either faking the effects or experiencing a "placebo effect" by unconsciously convincing themselves that they are high.

The day i tried an 'I-Dose'

It is a feeling akin to listening to the incessant drone of the local pub bore, without the option of politely grabbing your drink and moving on.

Yet according to the I-Doser.com website, if you spend 35 minutes listening to its alcohol "I-Dose" – which unlike most of its other offerings is provided free of charge – it will be the same as "shot-gunning five glasses of gin, in force".

"The effects come on strong, but mellow fast, and ease into a condition of relaxation, flightiness and overexcitement. Some have even experienced pure drunkenness from a single dose," it states proudly.

Settling down in a dimly lit room without any noisy distractions (as advised), it was just me and the I-Dose I had downloaded to my computer. Once launched, I was greeted by two sounds through my headphones.

These can best be described as a high-pitched sound coupled with a whirring or 'static' type noise similar to the sound of helicopter blades rotating.

After about 10 minutes, I was thoroughly bored, slightly relaxed – and had the beginnings of a headache.

Eventually, the 'static' sound was reduced while the high-pitched sound came to the fore in waves. This process continued until the sound changed again, and the static noise returned to prominence. Finally, it was all over.

Standing up from my place of comfort, I wondered if I really would be as unsteady on my legs as if I had drunk five shots of gin.

After 35 minutes of clearing my head to focus on the track, I definitely felt calmer. But I was also completely sober, and my suspicion is that I would have been just as relaxed if I had spent 35 minutes listening to Pink Floyd.

While the use of binaural beats may be a valid form of therapy, it is surely a leap to claim, as I-Doser does, to be able to recreate the specific effects of drugs such as alcohol, marijuana and cocaine.

"Best of all, no hangover," I-Doser also proclaims about its product.

Then again I was not drunk, either.