Propoxyphene is an opioid pain reliever used to treat mild to moderate pain and it acts as a cough suppressant. It is structurally similar to methadone and its metabolite with a half-life of 8 – 24 hours. Since 2010, the FDA recommends avoiding the use of propoxyphene due to its toxic effect on the heart, even when used at therapeutic doses. Propoxyphene is typically measured in urine as part of a drug of abuse test.