Awake doesn't mean safe. The lungs can still be losing.
Someone hands you a naloxone kit and tells you it can save a life. That has been true, and it still can be — but a new study published in the May 2026 issue of Anesthesiology suggests the story is more complicated than the packaging implies, particularly when the opioid involved is fentanyl or something even stronger.
The research, led by Maarten A. van Lemmen of the Department of Anesthesiology at Leiden University Medical Center in the Netherlands, enrolled 30 participants and examined how well standard naloxone doses reversed the respiratory effects of potent synthetic opioids. The participants included both opioid-naive individuals and daily opioid users — a range that reflects the real-world population most likely to encounter an overdose situation. What the team found was unsettling: a single dose of naloxone does not always fully reverse the breathing suppression caused by drugs like fentanyl and sufentanil.
The stakes are not abstract. Fentanyl and fentanyl-like compounds now account for somewhere between 60 and 79 percent of all overdose deaths in the United States. These drugs bind to opioid receptors with far greater tenacity than older opioids like heroin or oxycodone, which means the standard reversal dose — calibrated for a different era of the crisis — may simply not be enough to dislodge them. The opioid crisis has evolved; the tools used to fight it, the study argues, have not kept pace.
One of the study's most clinically significant findings involves a dangerous gap between appearance and reality. When naloxone is administered, a person may open their eyes, respond to their name, and seem to have returned from the edge. But according to an accompanying editorial by James P. Rathmell, editor-in-chief of Anesthesiology and a professor at Harvard Medical School, and Steven E. Kern of the University of Utah, that apparent alertness can mask a respiratory system that is still failing. Breathing may remain slow and inadequate even as the person looks awake. With very potent opioids like sufentanil, this mismatch between outward responsiveness and actual physiological recovery can be especially pronounced.
Rathmell and Kern describe this as having direct implications for how patients are observed and how dosing decisions are made. It helps explain something that has long puzzled emergency responders: why people sometimes slip back into crisis — what clinicians call resedation — even after naloxone was given promptly and the person initially seemed fine. The naloxone wore off. The opioid did not.
Van Lemmen's team is direct about what this means in practice. Calling 911 the moment an overdose is suspected remains essential, even if naloxone has already been administered. The drug buys time; it does not guarantee safety. Additional doses may be necessary, and the person needs to be monitored continuously until professional medical help takes over.
The study also points to a structural problem. The guidelines that govern overdose response were written for a drug landscape that no longer exists. The opioids driving today's deaths are categorically more potent than those the protocols were designed around, and the researchers argue there is an urgent need to revise those guidelines and to develop reversal tools better matched to what is actually circulating on the street.
For anyone who carries naloxone — a family member, a harm reduction worker, a bystander trained in overdose response — the message is not that the drug is useless. It is that the drug is one part of a response, not the whole of it. Giving it and walking away, or giving it and assuming the person is safe because they opened their eyes, may no longer be enough. The call to 911 is not optional. The watching and waiting is not optional. And the institutions that set the rules for how overdoses are managed now have a peer-reviewed case for why those rules need to change.
Notable Quotes
The current doses of naloxone may not be sufficient to reverse overdoses caused by newer synthetic opioids — these findings should encourage institutions to update guidelines and reinforce the importance of fast emergency intervention.— Maarten A. van Lemmen, Ph.D., lead study author, Leiden University Medical Center
The distinction between appearing awake and truly recovering has immediate implications for patient safety, observation practices, and dosing strategies — and helps explain why resedation continues to occur despite timely naloxone administration.— James P. Rathmell, M.D., and Steven E. Kern, Ph.D., editorial authors in Anesthesiology
The Hearth Conversation Another angle on the story
Why does it matter that these opioids bind more tightly to receptors? Isn't naloxone just supposed to knock them off?
That's exactly the mechanism — naloxone competes for the same receptor sites. But when a drug like fentanyl holds on harder, a standard dose of naloxone may only partially displace it. You get partial reversal, not full recovery.
So the person might look okay but still be in danger?
That's the core finding. The brain can register enough naloxone to produce wakefulness before the lungs have recovered enough to breathe safely. The two systems don't come back online at the same rate.
That seems like something emergency responders would already know.
Some do, but the guidelines haven't formally caught up. They were built around older opioids — heroin, prescription painkillers — where the reversal was more complete and more durable. Fentanyl changed the math.
What about the naloxone wearing off before the opioid does?
That's the resedation problem. Naloxone has a shorter half-life than fentanyl in many cases. The person wakes up, the naloxone clears, and the fentanyl is still there. Without someone watching, that can be fatal.
Does this mean the current naloxone doses are just wrong?
Not wrong for what they were designed for. Insufficient for what the crisis has become. That's a meaningful distinction — it's not a failure of the drug, it's a mismatch between the tool and the threat.
What would updated guidelines actually look like?
More emphasis on multiple doses, mandatory 911 calls regardless of apparent recovery, longer observation windows. And on the research side, better reversal agents designed specifically for high-potency synthetics.
Is sufentanil actually showing up in street drugs?
The study uses it as a research model because of its extreme potency — it's a useful stress test for the reversal question. But the broader class of fentanyl analogs is very much present in the illicit supply.
What's the single thing a bystander should take away from this?
Give the naloxone, then call 911 anyway. Awake does not mean safe. Stay with the person. The drug bought time — don't assume it finished the job.