What kind of pill that is yellow, round and has op on one side and 40 on the other side?

Not medical advice: A yellow round pill with an OP 40 imprints is OxyContin. It is in a group of drugs called narcotic pain relievers.

Tags: the other sidedrugspill 
Thursday, February 02 2012
Source: http://www.drugs.com/search.php?q=OxyContin