The number of new types of drug being uncovered by authorities has quadrupled in the past five years, says Scotland's drug enforcement agency.
Substances such as 'legal ket' (methoxetam- ine) and 'mad cat' (meph- edrone and phenazepam which is close to the tran- quilliser diazepam) are emerging at the rate of one a week across Europe.
The Scottish Crime and Drug Enforcement Agency said 48 new, unlicensed drugs were "discovered" last year, up from just 10 five years ago.
The findings were announced by the SCDEA in its annual report.
Because these new drugs have not been officially tested, the effects on people are unknown and SCDEA says the drugs are being marketed and trafficked through the internet.
One of the new drugs, known as Benzo Fury, was reportedly taken by a teenager who died at the RockNess music festival in the Highlands earlier this year, although the results of his toxicology report are not yet known.
Andrew Cunningham of the SCDEA said: "It is difficult to keep up with. Methoxetamine, for example, is so close to ketamine in structure but it avoids the law: it has the same effects and the same harms.
"It is a small proportion of what is out there in Scotland but it is growing all the time.
"The big issue is that they are untested and people don't know what their effects will be.
"It is causing concern for us due to the dangers.
"People think as they are legal, they think they are safe.
"However, they are not."
And according to the agency's Kenny Simpson: "There is often no information about the dose.
"This often leads to people taking them in far greater amounts than they should be.
"You can buy them on the internet and have them delivered to your door - but there is no good news around this."
Meanwhile, the SCDEA says it is using new tactics to disturb the activities of organised criminals.
It said it disrupted such groups on 109 occasions in 2011-2012: twice as many as in the previous year.
Forty-two of the interventions were classed as high-level, meaning they had a significant impact on serious criminal activity, the agency says.
The report says 194 people were arrested, 75 of these being the "most harmful and dangerous criminals" known to the police.
The SCDEA says it seized 782kg of illicit drugs, said to have a street value of around £18.5million, over the year period.
That included 40kg of cocaine and 100kg of ecstasy.
Deputy chief constable Gordon Meldrum, SCDEA director gen- eral, said: "We want to ensure that our disruptive activity makes life as difficult as possible for the organised serious crime groups which we are targeting at this time."
He concluded: "The more we continue to disrupt serious organised crime in this way, the safer 5.2m people – and our economy – are from harm."