What drugs will show up in a drug mouth swab?

A swab test doesn't detect drugs. A swab test detects infections.

I must disagree. Swab tests are often used to sample infections, but can and, in some places, are used to detect concentrations of certain drugs, usually recreational, in the human system.

Actually YES they do & they're quite effective as it is difficult to mask saliva...the tests are given in a group setting, and the saliva test is tamper-proof...i work in risk management, and this is becoming a more prevalent means of testing. The way it works is; swab is given, read & immediately placed in a sealed sleeeve. The test doesnt pin-point a specific drug, however, ANY substance detected will give a "probable cause" result. At this point, the swab is sent to the lab to determine EXACTLY what drug has been detected in the saliva...i've yet to see anyone skirt this test (your saliva doesnt lie)