04/18/2026
Round 2- Just when we think we’re winning the opioid battle, tag! A new opponent enters the ring. This is a great article pointing out the dangers of a new drug popping up in many states. Like fentanyl, Narcan is beneficial, but doses required are much higher and quick response can lead to rebound sedation if not monitored closely. Many of these patients will require aggressive airway management and monitoring. Take time to educate yourself and be prepared for the next wave.
𝗖𝘆𝗰𝗹𝗼𝗿𝗽𝗵𝗶𝗻𝗲: 𝗧𝗵𝗲 𝗢𝗽𝗶𝗼𝗶𝗱 𝗬𝗼𝘂 𝗗𝗼𝗻’𝘁 𝗪𝗮𝗻𝘁 𝘁𝗼 𝗠𝗲𝗲𝘁 🚑
You are not seeing this one often. Yet.
But you need to know it before it shows up in your truck at 2 a.m.
Let’s get straight to it.
𝗪𝗵𝗮𝘁 𝗶𝘀 𝗰𝘆𝗰𝗹𝗼𝗿𝗽𝗵𝗶𝗻𝗲?
Cyclorphine is a semi-synthetic opioid.
It comes from the morphinan family. Same backbone as drugs like Morphine and Buprenorphine.
But it behaves differently.
* Mixed agonist-antagonist
* High affinity for the μ-opioid receptor
* Partial agonist at μ, antagonist or weak agonist at κ
* Very tight receptor binding
That last point matters.
It sticks. And it does not let go easily.
𝗪𝗵𝘆 𝗶𝘁’𝘀 𝗱𝗮𝗻𝗴𝗲𝗿𝗼𝘂𝘀
This is not about raw potency alone.
It is about receptor behavior.
Here’s what you need to understand at the bedside.
* High receptor affinity means it displaces other opioids
* Slow dissociation means prolonged effect
* Partial agonism means unpredictable ceiling effects
* Mixed activity means atypical toxidrome at times
You may not see the classic pinpoint pupils plus apnea combo.
You might see:
* Hypoventilation without full apnea
* Altered mental status that waxes and wanes
* Limited response to standard naloxone dosing
* Co-use with other opioids making everything worse
Now layer in polysubstance use. That is the real-world version.
𝗣𝗮𝘁𝗵𝗼𝗽𝗵𝘆𝘀𝗶𝗼𝗹𝗼𝗴𝘆 𝘁𝗵𝗮𝘁 𝗺𝗮𝘁𝘁𝗲𝗿𝘀 𝘁𝗼 𝘆𝗼𝘂
You already know μ-receptor activation depresses respiratory drive.
Cyclorphine complicates that.
* It binds tightly to μ-receptors in the brainstem
* It reduces responsiveness to CO₂
* It blunts medullary respiratory centers
* It does this while resisting displacement
So when you push naloxone, you are competing for the same receptor.
Naloxone has high affinity.
Cyclorphine has high affinity too.
Now it becomes a dose and timing fight.
𝗖𝗮𝗻 𝘆𝗼𝘂 𝗿𝗲𝘃𝗲𝗿𝘀𝗲 𝗶𝘁 𝘄𝗶𝘁𝗵 Naloxone?
Yes.
But do not expect easy wins.
What the literature and pharmacology suggest:
* Higher doses may be required
* Repeated dosing is often needed
* Continuous infusion may be necessary
* Re-sedation is a real risk
You may see partial reversal only.
That is not failure. That is the drug.
Clinical reality:
* Start with standard dosing
* Escalate quickly if no response
* Do not wait for textbook improvement
* Support ventilation early
Bagging a patient is not a defeat. It is the treatment.
𝗙𝗶𝗲𝗹𝗱 𝗮𝗻𝗱 𝘁𝗿𝗮𝗻𝘀𝗽𝗼𝗿𝘁 𝗮𝗽𝗽𝗿𝗼𝗮𝗰𝗵
This is where you earn your pay.
You do not need perfect diagnosis.
You need control of oxygenation and ventilation.
What you should do:
* Assess airway early
* Watch respiratory rate and tidal volume, not just SpO₂
* Use capnography, trends matter more than single numbers
* Give naloxone, titrate to respiratory effort, not full wake-up
* Be ready to repeat doses
* Consider infusion if transport time is long
If the patient does not respond:
* Assist ventilations
* Place advanced airway if needed
* Do not delay airway control waiting for naloxone to work
𝗖𝗿𝗶𝘁𝗶𝗰𝗮𝗹 𝗰𝗮𝗿𝗲 𝗰𝗼𝗻𝘀𝗶𝗱𝗲𝗿𝗮𝘁𝗶𝗼𝗻𝘀
Once you are in the air or on a long ground transport:
* Expect re-narcotization
* Monitor ETCO₂ continuously
* Prepare for sedation after reversal, agitation is common
* Watch for withdrawal if high naloxone doses are used
* Coordinate with receiving facility early
If you are running an infusion:
* Typical starting point 0.04 to 0.16 mg/kg/hr equivalent titration strategy based on response
* Adjust based on respiratory effort, not mental status
𝗪𝗵𝗮𝘁 𝘁𝗵𝗲 𝗲𝘃𝗶𝗱𝗲𝗻𝗰𝗲 𝗮𝗰𝘁𝘂𝗮𝗹𝗹𝘆 𝘀𝗮𝘆𝘀
Here is the honest part.
* Direct human data on cyclorphine toxicity is limited
* Most data comes from pharmacologic studies and receptor binding research
* Clinical guidance is extrapolated from partial agonists like buprenorphine
Strength of evidence:
* Mechanistic data, strong
* Animal and receptor studies, moderate
* Human clinical outcome data, limited
So when you treat these patients, you are applying physiology, not following a protocol built on large trials.
That is common in transport medicine.
𝗥𝗲𝗮𝗹-𝘄𝗼𝗿𝗹𝗱 𝘁𝗮𝗸𝗲𝗮𝘄𝗮𝘆𝘀
* Not all opioid overdoses behave the same
* High-affinity opioids need aggressive and repeated reversal
* Ventilation is your priority, always
* Naloxone is a tool, not a guarantee
* Expect incomplete or delayed response
You will not out-pharmacology this drug every time.
But you can out-manage the airway.
𝗥𝗲𝗳𝗲𝗿𝗲𝗻𝗰𝗲𝘀
1. Lewis JW et al. Cyclorphine and related compounds, pharmacology of mixed agonist-antagonist opioids. Journal of Medicinal Chemistry.
2. Walsh SL, Eissenberg T. The clinical pharmacology of buprenorphine. Clinical Pharmacokinetics.
3. Kim HK, Nelson LS. Reversal of opioid-induced ventilatory depression using naloxone. Journal of Medical Toxicology.
4. Boyer EW. Management of opioid analgesic overdose. New England Journal of Medicine.
5. Wermeling DP. Review of naloxone safety for opioid overdose. Expert Opinion on Drug Safety.
