How long after you were dosed with rohypnol will it still show up in your blood or urine?

Half life. of flunitrazepam/rohypnol is 18-26 hours. We use the term "half life" to get an idea of how long a drug/medication will stay in a person's system. The half life is how long it takes for half of the medication to be metabolized. So you can see some traces of this drug could still be in your system for 2-3 days. Stay well!