How long does .5 mg of ativan end contained by your system?

How long does .5 mg of ativan end contained by your system?
The half natural life of lorazepam is 10 - 20 hours according to Professor Heather Ashton's Benzodiazepine Equivalence and Half Life Table. See here http://www.bcnc.org.uk/equivalence.html...
So basically partially of it is gone within 10 - 20 hours. After a daytime or 2 or max 3 days you shouldn't be feeling the effects. However if you own been using ativan or any other anaesthetic hypnotic type drug (tranquillisers and sleeping pills) longer that a few weeks or months you may experience benzodiazepine withdrawal symptoms which can drag on for months after stopping taking a benzodiazepine similar to ativan. See this page http://www.bcnc.org.uk/symptoms.html...
Hope this answers your question.
According to my drug book its 8-12 hours.
I grain the effects of it for 6 hours.
When I was takeing Ativan at this does I individual felt it for roughly 3-4 hours. I don't know how long it stays in your system.but I have to get bad of it because it stopped working for me after 2 weeks. I was even upping the dose and still nought. How often are you takeing it?