a drug that makes you want to sleep, and which can make you unable to remember what happens for a period after you take it Culture Rohypnol is the brand name of the drug Flunitrazepam which is used in some countries to treat insomnia (= the condition of being unable to sleep). It has become known as a date-rape drug and has been used to commit sexual assaults. The drug makes people relax and causes amnesia (= when someone cannot remember what has happened to them) and is given to victims secretly, for example in a drink. Rohypnol pills have now been changed so that they turn blue when added to liquids. Word Origin 1970s: invented name.