I have to second PG if you want to pass don't use!! but the simple answer if you took 20mg on the 25th and NOTHING ELSE you should be fine on the 1st most opiates have around 72 of life in the body for a URINE test good luck.
Ive done a lot of research on testing. I've found the best way to pass the test is to not take the pills.
Cheers,
no you will be fine. Unless they do a hair folical test. depending on how long your hair is it will show up for months. was it your prescription? if not your playing a dangerous game