FDA has sent warning letters to four online networks operating 21 websites for illegally marketing unapproved, misbranded opioids, including tramadol, the agency announced Tuesday (Aug. 28). Tuesday's action marks the second time since June that the agency has issued warning letters to internet firms for illegal marketing of opioids and other unapproved drugs, bringing the total number of warning letters to 13 issued to more than 70 websites, agency chief Scott Gottlieb says. The most recent round of warning letters...