Do pain meds metabolize differently?

Does anyone know if pain meds metabolize differently for us?  I'm being treated for a lumbar strain and muscle spasms and have been on Norco and Flexeril.  Yesterday, I went for a drug test for a new job and it had been two days since my last dose of Norco, yet it did not show up on the drug test.  Also, I've noticed that it does not last as long as it should.

 It probably has more to do with absorbtion than metabolism, plus your liver probably does move stuff through a bit faster as it has a lot less to do than before.

I can't imagine any reason they would. With the VSG, there's no change in the intestines, and those drugs are not absorbed in the stomach at all.

It also depends on what type of drug test they do- there's a 5 panel and a 9 panel. It might be that what you are taking does not show up in the 5 panel test, which is what employers commonly use (unless you're a truck driver or something else that gets a DOT-required test).

It was a 5 panel, it tested for Opiates and I take Norco (an opiate.)  This is just what I think based on my experience, they seem to kick in faster and then wear off faster.  Like maybe they absorb faster then metabolize faster.  I'm not saying there is malabsorption, I mean it's just faster.