a friend of mine did that same thing. He rarely smoked but did a couple days before a ua. he took some niacin pills, twice, to get the impurities out of his system and it worked. he got the job.
you just have to deal with your skin turning red and itching like a sunburn for a few hours.
the first day on the job he asked his new employer,"so how did the ua turn out?"
the employer said "obviously well since you're here".
At that point i realized I should have never asked that question.
I learned a good lesson that day