he opioid crisis just keeps getting worse, in part because new types of drugs keep finding their way onto the streets. Fentanyl, heroin’s synthetic cousin, is among the worst offenders.

It’s deadly because it’s so much stronger than heroin, as shown by the photograph above, which was taken at the New Hampshire State Police Forensic Laboratory. On the left is a lethal dose of heroin, equivalent to about 30 milligrams; on the right is a 3-milligram dose of fentanyl, enough to kill an average-sized adult male.

Fentanyl, according to the Centers for Disease Control and Prevention, is up to 100 times more potent than morphine and many times that of heroin.


Drugs users generally don’t know when their heroin is laced with fentanyl, so when they inject their usual quantity of heroin, they can inadvertently take a deadly dose of the substance. In addition, while dealers try to include fentanyl to improve potency, their measuring equipment usually isn’t fine-tuned enough to ensure they stay below the levels that could cause users to overdose. Plus, the fentanyl sold on the street is almost always made in a clandestine lab; it is less pure than the pharmaceutical version and thus its effect on the body can be more unpredictable.

Heroin and fentanyl look identical, and with drugs purchased on the street, “you don’t know what you’re taking,” Tim Pifer, the director of the New Hampshire State Police Forensic Laboratory, told STAT in an interview. “You’re injecting yourself with a loaded gun.”

New Hampshire, like the rest of New England, has been particularly hard hit by the opioid epidemic. The state saw a total of 439 drug overdoses in 2015; most were related to opioids, and about 70 percent of these opioid-related deaths involved fentanyl. The state has seen 200 deadly opioid overdoses this year so far, said Pifer.

Fentanyl was originally used as an anesthetic. Then doctors realized how effective it was at relieving pain in small quantities and started using it for that purpose. In the hands of trained professionals — and with laboratory-grade equipment — fentanyl actually has a pretty wide therapeutic index, or range within which the drug is both effective and safe.

The difference in strength between heroin and fentanyl arises from differences in their chemical structures. The chemicals in both bind to the mu opioid receptor in the brain. But fentanyl gets there faster than morphine — the almost-instantaneous byproduct when the body breaks down heroin — because it more easily passes through the fat that is plentiful in the brain. Fentanyl also hugs the receptor so tightly that a tiny amount is enough to start the molecular chain of events that instigates opioids’ effects on the body.


Sign up for our Morning Rounds newsletter

Please enter a valid email address.

This tighter affinity for the opioid receptor also means more naloxone — or Narcan — may be needed to combat a fentanyl overdose than a heroin overdose.

“In a fentanyl overdose, you may not be able to totally revive the person with the Narcan dose you have,” said Scott Lukas, director of the Behavioral Psychopharmacology Research Laboratory at McLean Hospital in Belmont, Mass. “Naloxone easily knocks morphine off of the receptor, but does that less so to fentanyl.”

Matt Ganem, a former addict, explains the excruciating process of opioid withdrawal. Alex Hogan/STAT

Leave a Reply to Nichole and joe Cancel reply

Please enter your name.
Please enter a comment.

  • @LAD You nailed the problem that is the root of the problem.
    CIA operatives have said many times, “Its not the drug addiction, it’s the cash flow addiction.”
    Look no further than Portugal that legalized all drugs and addiction rates dropped to over 60%.
    Black market, Physician RX, the links in the chain, the anchor the Cash Flow Addiction.

  • I think you actually missed the most important reason of why Fentanyl is more dangerous than heroin, it has a much narrower therapeutic index, it is a more powerful respiratory depressant.

    • Hi Melanie– the therapeutic index is the “window” between the minimum dose you need for the desired effect (pain relief or getting high) and the minimum dose that will poison or even kill you.

      Some opioids have a wide window–if you take significantly more than you need, even double or triple, it won’t necessarily be a medical emergency. Overshoot by just a little on fentanyl, which has a narrow window, and you can end up comatose or dead from respiratory depression.

      Because the dose that kills you is only slightly more than the dose that gets you high, and because the absolute amount of physical substance is so ridiculously small either way, ODing is very easy to do if you can’t accurately measure out microgram quantities of the drug, or if you believe you’re injecting something far less potent, like heroin.

  • Drug problem will never take care of itself. Ridiculous comment. Destroy the cartels,strong families and good jobs will go a long way. Education too.

  • I have been on opioid prescribed medication since 2011. I was able to stop for one (1) year after surgery ( I was pain free. In 2013-2014). 2014 I was in an auto accident an reinjured my back upon the impact and have been back on opioid prescription since. I know that if there were a way to live and keep the pain manageable without the drugs I would be happy to do so, however, at this time this is not possible. Some of you say that because a person has taken the drug so long they are addicted to it-Isomewhat true-my body is addicted, my mind is not. The year I was able to live without the drugs, I was weaned off and never missed them. I know I would be able to do that again at any time. I realize that I am lucky in that aspect and there are people who have addictive personalities. Those people need to seek help. If I were one of them, I would seek help! War on Drugs is not helping-We need to take the money out of the equation. Stop making it worth money to people. That is when the drug problem will stop. Once the money is no longer good enough to sell, make, produce, & traffics the drugs that is when the drugs will no longer be an issue. Take the money and put it toward healing, educating, rehab, and reform. Get the commercials back on tv “This is your brain on drugs”. Teach our kids as we taught them about drinking and driving. STOP JUDGING and start understanding that addiction is a problem that needs help. Know where to get help or send a person for help. REAL HELP! We need to STOP babies from being born addicted, mothers addicted when they get pregnant, fathers addicted when they impregnate the mother. These drugs have changed our DNA to the point that more children today are born with mental and physical defects then ever before in history. I have four (4) grand kids from the same son and daughter-in-law, of the 4 children, 1 has ADD, 1 has ADHD, 1 has Autisum (mild). Me, their grandfather, their father, their mother had never taken drugs, but their grand mother on their mom’s side was addicted to non prescription drugs. THREE (3) of my grandchildren suffer via DNA because of her drug use.

    We need to take the money out of the equation, educate our children & the drug problem will resolve it’s self.

    • I wish it was that simple. Drugs has always been big business so don’t know how you take money out of equation. Education is definetely important as is having a good,fulfilling job,purpose in life and strong family ties so people dont turn to drugs in the first place.Many of the people addicted don’t have addictive personalities. We have to work with other countries too and destroy the cartels like President Calderon was doing in Mexico in early 2000’s. Then we can hopefully reverse this epidemic for good.

    • The problem is that Western governments base their economies on the services that are suppose to help, 80% of the British economy is so irradiating the war on drugs diminishes it’s economy. Yet the users suffer while the suits exploit the derivertives in currencies due to the fluctuating markets because of BREXIT. Need real reforms ASAP

Sign up for our Morning Rounds newsletter

Your daily dose of news in health and medicine.