Coffee lovers who want to perk up their sex lives have been warned not to buy the caffeine-based drinks that contain a substance similar to Viagra.

Food Standards Australia New Zealand is warning consumers not to consume such drinks called Sexpresso and Rock Hard as they don't warn customers that they contain analogues of sildenafil (Viagra) on the label.

Tests have shown that the drinks contain chemicals similar to Viagra. There is a ban against adding therapeutic drugs or their analogues to foods.

"State and territory food enforcement agencies are currently investigating the products, which are being sold as an instant coffee product, and have been available on the internet and in adult shops," FSANZ said.

It is still unclear what side-effects the drugs could have aside from sexual enhancement.

"These analogues, like any drugs can interact with prescription medicines and may be dangerous, particularly for people with certain health conditions,'' a FSANZ alert reads.

"Consumers who are using this product should stop taking it immediately and speak to a doctor if they are experiencing side effects.''

There have been several instances where government has called for a food recall because of the presence of prescription medicines in foods.

FSANZ warns consumers to be cautious of food products that make claims about treating physical conditions.

"They should speak to their doctor before taking these products as even natural products can interfere with prescription medicines."