In turn, Phenytoin may lower clonazepam plasma levels by increasing the speed of clonazepam clearance by approximately 50% and decreasing its half-life by 31%. Clonazepam increases the levels of primidone [95] and phenobarbital. Hello ReitaErin, You didn't mention if you're being tested, but Klonopin(Clonazepam) is a long acting drug, has a half life of approximately 34 hours, benzos typically test positive in the urine for about 3 days after ingestion unless you are on the drug on a regular basis. For clonazepam, its elimination half-life ranges from 30 to 40 hours. This means that it will take between one to two days for just 50% of Klonopin to leave your system. Alprazolam (Xanax) and Clonazepam (Klonopin) are both benzodiazepines that help to calm anxiety, and treat other disorders. Alprazolam (Xanax) is used to treat anxiety disorders, panic disorders, and anxiety associated with depression. The elimination half-life of Clonazepam is typically 30 to 40 hours. Clonazepam pharmacokinetics are dose-independent throughout the dosing range. There is no evidence that Clonazepam induces its own metabolism or that of other drugs in humans. Doctors give trusted answers on uses, effects, side-effects, and cautions: Dr. Grin on xanax vs klonopin half life: The half-life for Xanax (alprazolam) XR is short 10.7–15.8 hours and the longer-term efficacy of Xanax (alprazolam) XR has not been systematically evaluated. Klonopin has an unusually long elimination half-life of 18–50 hours. Best Answer: Clonazepam is a long acting benzodiazepine with a half-life of 20-50hrs. It is most likely to be detectable for 3-4 days but it varies greatly on the individual. Clonazepam has a long elimination half-life within the range of 30 to 40 hours. This means that it will take between 1 and 2 days just to have eliminated 50% of the drug from systemic circulation. This means that it will take between 1 and 2 days just to have eliminated 50% of the drug from systemic circulation. Clonazepam half life If this is your first visit, be sure to check out the FAQ. You may have to register before you can post: click the register link above to proceed.