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.
The researchers tried out their system on volunteers who took between 0.5 and 4 milligrams of Rohypnol. For those who took at least 1 milligram of the drug-a typical prescription dose-the test detected it in urine samples one week later while conventional tests did not. Urine samples from people who took no drugs or other benzodiazepines gave negative results.
People who work with the victims of drug rape welcome the idea of a simple test, available in police stations, that can detect Rohypnol beyond the 72-hour limit of the best existing antibody tests. They say it would be immensely valuable to women who suspect they have been subjected to drug rape after several days have elapsed. "It will give the police a fighting chance to actually catch rapists," says Graham Rhodes of the Roofie Foundation in Leeds, which gives counselling and legal advice to victims of the crime.
Sam Le of the Los Angeles County Sheriff's Scientific Services Bureau says that rapists usually drug their victims with at least 2 milligrams of Rohypnol, which the test should easily detect. But Walshe says cases that go to court would need to be backed up by more sophisticated and expensive methods, such as gas chromatography and mass spectroscopy.
Walshe says the test could also be miniaturised to allow women to test suspicious drinks. However, he says that the team does not currently have funds to develop the test further.
The Roofie Foundation operates a help line in Britain on 0800-783-2980. For more information on Rohypnol, and contact details for support groups in other countries, see http://www.newscientist.com
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