MAYO CLINIC ROCHESTER, Minn. — Surgical patients receiving the opioid tramadol have a somewhat higher risk of prolongeduse than those receiving other common opioids, new Mayo Clinic research finds. However, the Drug Enforcement Administration (DEA) classifies tramadol as a Schedule IV controlled substance, meaning it’s considered to have a lower risk of addiction and abuse thanSchedule II opioids, such as oxycodone and hydrocodone. The study was published...