Police have warned New Year's Eve revellers n pubs and clubs across Wales to be aware of the dangers of drink-spiking, with fresh cases reported over Christmas.
Drugs used to spike drinks are often colourless and odourless
Officers said that a campaign launched by all four Welsh forces in the lead-up to Christmas had helped raise awareness of drink-spiking, which is believed to be behind a series of rapes and sexual assaults across the UK.
Gwent Police said that since the launch of the "Spiked" campaign on 11 December, there had been seven reported cases of drink-spiking in their force area.
In one case, a woman had to be taken to Nevill Hall Hospital, Abergavenny, after having her drink spiked in a pub in Abertillery.
Police said that she was suffering psychological effects from the incident.
The majority of the other incidents reported to the Gwent force took place in pubs and clubs in Newport.
Sedative drugs such as GHB and Rohypnol, which are odourless, colourless and tasteless, can be added to drinks to incapacitate victims, many of whom have little memory of what has happened to them.
Drugs Education Officer, Detective Constable Lyn Webber, of Gwent Police, said: "I want to urge the public to be aware of drink spiking and take precautions to make sure they don't become a victim.
"Drugs such as GHB and Rohypnol are odourless, colourless and tasteless.
"My advice is don't leave your drink unattended, don't accept drinks from strangers, avoid unfamiliar places and don't make yourself a target by drinking alcohol to excess.
Police are warning pub-goers to watch their drinks
"Keep an eye on your drink and don't let someone spoil your New Year."
Dewi Roberts, drug and alcohol reduction officer with North Wales Police, said that the force had received no reports of drink-spiking cases over Christmas, but that the campaign had raised awareness of the problem.
"We get about three cases a year in north Wales," he said.
"But the concern is how many cases are not being reported.
"As a result of the campaign, licensed premises, casualty units and North Wales Police have got a better understanding of the problem.
"We are finding that in venues across the force area, people are more aware of drink-spiking."
Dyfed-Powys Police and South Wales Police both said that they did not yet have statistics on drink-spiking from the Christmas campaign, which is due to end early in January.