With the increase in overdoses due to illicit fentanyl, which is many times more potent (the amount depends on the analog and the particular mix) than heroin, we wondered if medication-assisted treatment with methadone, buprenorphine or naltrexone would be effective for fentanyl users. Do trials need to be done with these medications for each specific opioid? Would methadone or buprenorphine block the effects of fentanyl or prevent an overdose? Would naltrexone? Or if these medications work for one opioid of abuse, do they work for all of them?
We put the questions to the experts at the National Institute on Drug Abuse (NIDA). Here is the response, from David McCann, Ph.D., associate director of NIDA’s Division of Therapeutics and Medical Consequences:
“As you know, opioid users often use whatever opioid is available for purchase on the street, and the identity of the opioid is often not known by the user. For example, something sold as ‘heroin’ may actually be fentanyl, and counterfeit pills are sometimes manufactured and sold on the street (e.g., tablets with numbers and letters imprinted to match oxycodone have been found to contain fentanyl). Likewise, if someone thinks they are buying fentanyl, it may be something else, and it’s not uncommon for heroin and fentanyl to be mixed. All of the commonly abused opioids (heroin, morphine, oxycodone, hydrocodone, fentanyl, etc.) work in the same way. If a researcher were to set out to do a study of patients who only abuse fentanyl, and potential subjects were screened for several weeks prior to study enrollment with daily urine testing to exclude subjects that use other opioids, it’s quite possible that all subjects would be excluded and no ‘pure fentanyl users’ would be found. While it’s possible that some methadone trials in the 1960s might have enrolled subjects who only used heroin, recent medication trials leading to the approval of buprenorphine and Vivitrol (once-monthly naltrexone) have enrolled subjects who met the criterion for opioid use disorder (or ‘opioid dependence,’ as it was previously called), and as a result the subjects had a mixed history of opioid use. Regardless of the opioid(s) that are abused, the medications work in the same way. A drug such as naloxone or naltrexone that blocks the effects of heroin also blocks the effects of fentanyl, by blocking the mu opioid receptor (where all of the commonly abused opioids act). Methadone and buprenorphine can alleviate opioid withdrawal signs and symptoms by stimulating mu opioid receptors regardless of the type of opioid (or opioids) that was being abused prior to withdrawal. Where fentanyl differs is in its potency. It takes just a tiny amount for someone to get high, and the amount required for an overdose is also quite tiny. That’s especially dangerous when someone doesn’t know that he/she is taking fentanyl.”