Potentially harmful drugs normally used in operating theatres are being sold in Nottinghamshire, police have said.
Officers believe the vials of liquid are being offered in the Worksop area.
They are concerned people may be trying to use the medication as a recreational drug and have warned this could be extremely dangerous.
The drugs, labelled as tracrium, atracurium, and atracurium besylate, is a powerful muscle relaxant and would be administered through a needle.
Pc Tracey Pavey said: "People may be using these drugs recreationally. They are usually administered by a trained medical professional and could be extremely harmful if not used correctly.
"We believe the drugs may be being sold in and around Worksop and I would urge anyone who knows who is selling them to please contact police."