Photograph by ,a href=”http://www.flickr.com/photos/kelvynskee/5027288100/”>Kevlyn Skee

Ketamine, the horse tranquiliser and popular “party drug”, is to have its classification upgraded from class C to class B.

The drug, often described as “Special K” and used by an estimated 120,000 people in Britain, is being reclassified due to the physical and psychological dangers it poses to users. The Advisory Council on the Misuse of Drugs recommended changing the drug to a class B restricted substance in a report two months ago after evidence emerged that long-term use can cause serious damage to a user’s bladder.

In reclassifying the drug, Minister for Crime Prevention, Norman Baker, said he was sceptical about the effectiveness of the drug classification system in reducing use, but hoped that the increased classification would warn people of the drug’s dangers.

The inadequacies of the classification system were highlighted in 2009 by Professor Nutt, former head of the Advisory Council on the Misuse of Drugs, when he criticised government policies towards both cannabis and ecstasy/MDMA saying their classification had little to do with the risks they posed.

Unlawful possession of ketamine as a class B substance will carry a maximum penalty of five years in jail, rather than two years under its previous class B status.

Announcing the reclassification, the crime prevention minister, Norman Baker, said he hoped to send a message that the drug is harmful. But he also signalled his scepticism over effectiveness of the 40-year-old classification system to control drug use.

Speaking at a drug treatment centre in west London on Wednesday, Mr Baker said: “What I do think is in the short term there’s a message that needs to be sent on ketamine. In terms of where we’re going in 20 or 30 years’ time, in terms of the optimum method of minimising drug use then I’m not sure.

“It certainly after all hasn’t stopped drug use by classification. But what it does do is send a message to those who are interested.

“You have to assume some drug users actually care about their bodies, therefore saying to them this is more dangerous than that, what they will take into account and what they will actually do.”