Scientists have told West Midlands Police that the body's natural response to a needle being pressed into skin would cause most people to move away from the pain, meaning the time for a spiker to administer enough drugs to affect someone via a syringe would be short.
West Mercia Police's assistant chief constable Damian Barratt said the news was "reassuring", but insists the force will still be targeting anyone displaying predatory behaviour.
“We hope that people find the information from our colleagues in West Midlands Police reassuring, however, I do want to be clear that this does not mean we are complacent around our response to drink or drug spiking. It is a serious crime.
“Anybody who thinks they have been injected or had their drink spiked should report this to us as soon as they can.
“We know that in the run up to Christmas more and more people will be visiting pubs and clubs across Herefordshire, Shropshire and Worcestershire and will be increasing the number of officers on patrol.
"Our plans for the Christmas period will complement our existing plans to help keep people safe by targeting predatory behaviour and those looking to exploit people enjoying a night out.”
A West Midlands Police statement said: "As we work hard to develop our understanding of spiking, we’ve been speaking to scientists about the use of syringes in bars and clubs. And their update should be reassuring.
"They told us that because of the body’s natural response to the pain that comes from a needle being pressed into the skin, most people react very quickly to being injected and move away from the pain.
"This reflex response combined with the time needed to press the syringe plunger, means the opportunity to inject the significant amount of drug needed to have an effect is limited, but not impossible."
Anyone concerned that someone they know may be involved in drink or drug spiking is encouraged to pass this information on anonymously to Crimestoppers on 0800 555 111, or visit crimestoppers-org.uk.