2 Answers - Posted in: klonopin, clonazepam - Answer: Klonopin's half-life is 18-50 hours.A drug leaves your system after 5 half-lives, thus, Klonopin should be out of your system in 2-3 days. However, half-life is affected by dose, as well, and 2mg is not a huge dose but it's a moderate one....