Sergeant Martin Bent from Bowral Police said patrons needed to be aware drinks could be spiked with alcohol as well as drugs.

"It's not just drugs that are used to spike drinks but alcohol. White spirits such as vodka are particularly hard to detect," he said.

"When you're drinking something that has double or triple the alcoholic content you're expecting, then you get intoxicated very quickly."

Sergeant Bent said drinks can be spiked as a prank or with the intent to assault, rob or sexually assault someone.

"We'd like to remind people that when they are out drinking, it's best to drink among people that you know," he said.

"It's also best to avoid shouts and having people buy you drinks."

Sergeant Bent advised Southern Highlands patrons not to drink anything they did not open or see opened or poured.

"Don't leave drinks unattended on tables and try to minimise the risk of drink tampering," he said.

Sergeant Bent said there were a number of symptoms of drink spiking patrons should be aware of.

"There can be quite a sudden onset of symptoms after your drink has been spiked including a loss of balance and slurred speech," he said.

"If it gets particularly nasty then there can be an be an increase in respiration and your pulse rate can rapidly escalate or slow down."

Sergeant Bent said it is important for people to monitor their drinking habits and notify friends and authorities if they start experiencing unusual symptoms. "A lot of people don't realise there's a problem until the critical stage, but things like blurry vision, unsteady feet and being unable to hold a conversation are all possible symptoms," he said.

"If you detect that your drink has been spiked then stop drinking immediately and try to find someone safe. It's always important to monitor how much you're drinking."