RAPISTS who drug their victims so that they don't remember what happened to them could soon be easier to catch, thanks to a test developed by scientists in Ireland. The simple urine test can detect the "date rape drug" Rohypnol up to a week after it has been taken.
Rohypnol is a powerful sedative used to treat insomnia. It has never been approved for use in the US, but is available in Europe on prescription. High doses can cause amnesia for up to 24 hours.
The tablets, known as "roofies", have no taste or smell when dissolved in water. Worldwide, thousands of women believe they have been raped after someone slipped Rohypnol into their drink. Hoffmann-La Roche, which makes the drug, has reformulated its tablets so that they turn drinks blue, but illicit tablets are still available on the black market.
Rohypnol belongs to a class of sedatives called benzodiazepines, which includes Valium. But it is 10 times as potent as other drugs in the class, and so is used in much smaller quantities, making it very difficult to detect. Existing antibody tests, developed for other benzodiazepines, often miss Rohypnol.
Kieran Walshe and his colleagues at University College Dublin have developed a more sensitive test. Working with a team at Trinity College, also in Dublin, they obtained antibodies to the major metabolite of Rohypnol, 7-aminoflunitrazepam. They also bound the metabolite to an enzyme that catalyses a reaction that causes a colour change.
For the test, the antibodies are fixed to a solid support and exposed to a urine sample mixed with the enzyme-linked 7-aminoflunitrazepam. Any metabolite present in the urine competes with the enzyme-metabolite complex, preventing it binding to the antibodies. The more metabolite there is in the sample, the less enzyme binds to the antibodies, and the weaker the colour produced. "We also pick up other metabolites and unmetabolised Rohypnol," says Walshe.