Carfentanil at a glance: schedule, half-life, and class
- Drug class
- Synthetic opioid agonist; fentanyl analog
- US legal status
- Schedule II (no approved human use)
- Approved uses
- Veterinary immobilization of large animals only
- Potency
- About 100 times fentanyl and 10,000 times morphine
- How it appears
- Mixed into counterfeit pills, heroin, and fentanyl powder
- Lethal amount
- Around 2 mg, or less, can be fatal
- Reversal agent
- Naloxone; multiple doses are often needed
What is carfentanil?
Carfentanil was synthesized in 1974 and marketed as Wildnil to immobilize animals such as elephants and moose. It has no approved medical use in people.[1]
It entered the US illicit drug supply in 2016 and caused clusters of deaths, then declined before re-emerging. CDC data show deaths involving carfentanil rose from 29 in January to June 2023 to 238 in January to June 2024, in 37 states.[1]
Carfentanil effects and how long they last
Carfentanil causes the same effects as other opioids, sedation, euphoria, and slowed breathing, but at microgram doses. The amount in a single grain can be enough to stop breathing in someone without tolerance.[1]
People rarely know they have taken it: it is usually mixed into heroin, fentanyl, or counterfeit pills sold as oxycodone or Xanax.[2]
Carfentanil side effects and risks
Overdose: breathing can stop within minutes. Even people with high fentanyl tolerance can overdose.[1]
Naloxone resistance: carfentanil binds tightly to opioid receptors, so overdoses often need more than one dose of naloxone, and breathing can slow again as naloxone wears off.[1][3]
Unknown dose: because it is mixed unevenly into other drugs, two pills or bags from the same batch can contain very different amounts.
Warning: Fentanyl test strips may not reliably detect carfentanil. Never use alone, carry naloxone, and call 911 for anyone who is hard to wake.
Carfentanil interactions: what is dangerous to mix with it
Choose what it would be combined with:
| Combined with | What happens | Guidance |
|---|---|---|
| Benzodiazepines (alprazolam, diazepam, clonazepam) | Profound sedation, slowed breathing, coma, death | Boxed warning; avoid unless no alternative |
| Alcohol | Stronger sedation and slowed breathing | Avoid |
| Gabapentin, pregabalin, sleep medicines, muscle relaxants | Additive sedation and breathing problems | Use caution; lower doses |
| Stimulants (cocaine, methamphetamine) | Masked sedation; overdose when the stimulant wears off | Dangerous |
| Xylazine or medetomidine | Deeper, longer sedation not reversed by naloxone | Dangerous |
This is not a full list. Combining substances raises the risk of harm, especially when the contents of street drugs are unknown.
Carfentanil overdose: signs and what to do
Carfentanil overdose causes pinpoint pupils, unresponsiveness, blue or gray lips, and slow or stopped breathing, often within minutes. Brief skin contact is very unlikely to cause an overdose, but responders should avoid handling powders without gloves.[1][3]
If someone may have overdosed
- Call 911 if the person is unresponsive, cannot be woken, has blue or gray lips, or is breathing slowly or not at all.
- Give naloxone (Narcan or a generic nasal spray, sold without a prescription) into one nostril. If there is no response after 2 to 3 minutes, give another dose.
- If you are trained, give rescue breaths. Otherwise place the person on their side so they do not choke.
- Stay with them. Naloxone can wear off before carfentanil does, so the overdose can return even after the person wakes up.
- Most states have Good Samaritan laws that protect people who call 911 for an overdose from some drug charges.
Carfentanil withdrawal timeline: symptoms and how long it lasts
People exposed regularly to carfentanil through the drug supply develop opioid dependence and withdrawal similar to fentanyl.[1]
- 4 to 12 hoursEarly symptomsAnxiety, restlessness, yawning, sweating, runny nose, watery eyes, and muscle aches.
- Days 1 to 3Peak withdrawalDiarrhea, cramps, vomiting, goosebumps, fast heartbeat, and strong cravings.
- Days 5 to 10, then weeksLingering symptomsPoor sleep, low mood, and cravings. Tolerance falls quickly.
Warning: Tolerance drops within days. Returning to previous use after a break is a leading cause of fatal overdose.
Buprenorphine and methadone treat opioid use disorder, including from fentanyl and its analogs, and cut the risk of death roughly in half.
Is carfentanil legal in the US? Schedule and legal status
Carfentanil is a Schedule II controlled substance because of its approved veterinary use. Possessing or selling it outside DEA-registered veterinary or research settings is a federal crime.[4]
- Possession: under federal law, a first conviction for possessing any controlled substance without a valid prescription can bring up to one year in prison and a minimum fine of $1,000. Penalties rise with prior convictions.[5]
- Trafficking: trafficking fentanyl analogs carries mandatory minimum sentences, and distribution resulting in death or serious injury carries 20 years to life.[6]
Where can someone get help with carfentanil use?
- SAMHSA National Helpline: 1-800-662-4357. Free, confidential, 24 hours a day, in English and Spanish. It gives referrals to local treatment and support.[7]
- FindTreatment.gov: a federal locator for state-licensed treatment programs, searchable by location, payment, and type of care.[8]
- 988 Suicide and Crisis Lifeline: call or text 988 for a mental health or substance use crisis.
- Your own clinician: a primary care doctor can screen, treat, and refer, and can discuss medicines that support recovery where they exist.
Carfentanil legal status in other countries
| Country | Status |
|---|---|
| United Kingdom | Class A |
| Canada | Schedule I of the Controlled Drugs and Substances Act |
| China | Controlled since March 2017 |
| International | Schedules I and IV of the 1961 Single Convention (since 2018) |
Laws change and differ in detail. Check current rules before carrying any controlled medicine across a border.[9]
Common questions about carfentanil
How strong is carfentanil?
About 100 times stronger than fentanyl and 10,000 times stronger than morphine.
Does naloxone work on carfentanil?
Yes, but several doses are often needed, and the person must be watched because the overdose can return.
Can you overdose by touching carfentanil?
Brief skin contact is very unlikely to cause an overdose, but powders should not be handled without gloves, and should not be inhaled.
Is carfentanil used in medicine?
Only in veterinary practice, to sedate very large animals. It has never been approved for people.
Is carfentanil back in the drug supply?
Yes. Deaths involving carfentanil rose about sevenfold between early 2023 and early 2024.
Sources
- Detection of Illegally Manufactured Fentanyls and Carfentanil in Drug Overdose Deaths, United States, 2021 to 2024. Centers for Disease Control and Prevention, MMWR, December 2024.
- One Pill Can Kill. US Drug Enforcement Administration.
- Information about naloxone and nalmefene. US Food and Drug Administration.
- Controlled Substance Schedules. DEA Diversion Control Division.
- 21 U.S.C. 844, Penalties for simple possession. Legal Information Institute, Cornell Law School.
- 21 U.S.C. 841, Prohibited acts A (trafficking penalties). Legal Information Institute, Cornell Law School.
- National Helpline. Substance Abuse and Mental Health Services Administration.
- FindTreatment.gov. Substance Abuse and Mental Health Services Administration.
- International drug control conventions. United Nations Office on Drugs and Crime.
