The Centers for Disease Control and Prevention and the Drug Enforcement Administration are investigating recent increases in overdose fatalities related to fentanyl, a synthetic opioid 50 to 100 times more potent than morphine, according to a CDC advisory this week. Most of the more than 700 fentanyl-related overdose deaths reported to DEA since late 2013 were attributable to illicitly-manufactured fentanyl mixed with heroin or other diluents, the agency said. The advisory includes recommendations for public health departments, health care providers, law enforcement and others to improve detection of fentanyl outbreaks and expand naloxone. For example, the agency recommends that health care providers keep more naloxone on hand for first responders, because multiple doses may be needed to treat a fentanyl overdose due to the drug’s potency.