I have only taken this type of test one time, for a job a United Healthcare. (2003) I had stopped smoking for 2 weeks (really 16 days) prior to taking this test, and I passed it. I tried to research it first on the internet, as I had never heard of this saliva test prior to that job, and according to what I read, it is not quite as effective as a urine test, meaning it will not go back as far. You can also google "saliva drug test" and I'm sure find the same info that I did. I don't think you could substitute anything for this type of test, as when I took mine, the human resources lady watched me do it. Good luck.