Opiates like heroin, morphine, oxycodone (Percocet, OxyContin), hydrocodone (Vicodin, Norco), fentanyl, and methadone constrict the pupils (myosis) when used. Cocaine, methamphetamine, and ecstasy/MDMA dilate the pupils (mydriasis) when used. Pupil size is usually the first physical characteristic police look for when someone is suspected of being under the influence (other than behavior).