Carfentanil POWDER or carfentanyl is a structural analog of the synthetic opioid analgesic fentanyl. Short acting and with fast onset, it has weight for weight, around one hundred times stronger effects than fentanyl and thousands of times stronger than heroin. It is more effective at reducing pain response in rats than any other opioid.

Carfentanil was first synthesized in 1974 by a team of chemists at Janssen Pharmaceutica which included Paul Janssen.

The effects of carfentanil, including overdose, can be reversed by naloxone.

Carfentanil is legally controlled in most jurisdictions, but has veterinary uses for anaesthetising large animals.

Typical use
Carfentanil was sold starting in 1986 under the brand name Wildnil for use in tranquilizer darts in combination with an ?2-adrenoreceptor agonist for large mammals including elk and elephants. It was chosen for its high therapeutic index. Commercial production of Wildnil ceased in 2003, and the drug is available only as a compounded dosage form.

Radiolabelled [11C]carfentanil is widely used as a selective radiotracer in animal and human positron emission tomography (PET) imaging studies of the ?-opioid system due to its high affinity for receptors.

Importation from China
According to an Associated Press article from 2016, Chemical weapon for sale: Chinas unregulated narcotic, fentanyl, carfentanil and other highly potent derivatives of fentanyl are actively marketed by several Chinese chemical companies. Carfentanil was not a controlled substance in China until 1 March 2017, and until then was manufactured legally and sold openly over the Internet.

Authorities in Latvia and Lithuania reported seizing carfentanil as an illicit drug in the early 2000s. Around 2016, the US and Canada started reporting a dramatic increase in shipment of carfentanil and other strong opioid drugs to customers in North America from Chinese chemical supply firms. In June 2016 the Royal Canadian Mounted Police seized one kilogram of carfentanil shipped from China in a box labeled printer accessories. According to the Canada Border Services Agency, the shipment contained 50 million lethal doses of the drug, more than enough to wipe out the entire population of the country, in containers labeled as toner cartridges for Hewlett-Packard LaserJet printers. Allan Lai, an officer-in-charge at the Royal Canadian Mounted Police in Calgary who helped oversee the criminal investigation said, With respect to carfentanil, we dont know why a substance of that potency is coming into our country.

Pharmacology
Carfentanil is a lipophilic chemical, and hence can much more easily cross the blood-brain barrier. :pg 9 It thus has very rapid onset of effects, but is also shorter acting.

For pain relief, a unit of carfentanil is 100 times as potent as the same amount of fentanyl, 5,000 times as potent as a unit of heroin, and 10,000 times as potent as a unit of morphine. This is despite only having 14-135 times higher affinity for the? receptor.

Legal status
China
Carfentanil has been controlled in China since 1 March 2017. The trade war between China and the US has included controversy over the effectiveness of this control.

United States
Carfentanil is classified as Schedule II under the Controlled Substances Act in the United States with a DEA ACSCN of 9743 and a 2016 annual aggregate manufacturing quota of 19 grams (less than 0.7 oz.).

United Kingdom
Carfentanil has been specifically controlled as a Class A drug since 1986

Chemical and physical data
Formula: C24H30N2O3

Molar mass: 394.515 g·mol?1