Carfentanil or carfentanyl (R-33799) is an analogue of the popular synthetic opioid analgesic fentanyl, and is one of the most potent opioids known (also the most potent opioid used commercially). Carfentanil was first synthesized in 1974 by a team of chemists at Janssen Pharmaceutica which included Paul Janssen. It has a quantitative potency approximately 10,000 times that of morphine and 100 times that of fentanyl, with activity in humans starting at about 1 microgram. It is marketed under the trade name Wildnil as a general anaesthetic agent for large animals. Carfentanil is intended for large-animal use only as its extreme potency makes it inappropriate for use in humans. Currently sufentanil, approximately 10–20 times less potent (500 to 1000 times the efficacy of morphine per weight) than carfentanil, is the maximum strength fentanyl analog for use in humans.
Moscow theater hostage crisis 
Recently, a new study found evidence supporting the claim that during the 2002 Moscow theater hostage crisis, the Russian military made use of an aerosol form of carfentanil and another similar drug, Remifentanil, to subdue Chechen hostage takers. Its short action, easy reversibility and therapeutic index (10,600 vs. 300 for fentanyl) would make it a potential agent for this purpose. Riches, et al., found evidence from liquid chromatography-tandem mass spectrometry analysis of extracts of clothing from two British survivors, and urine from a third survivor, that the aerosol comprised a mixture of the two anaesthetics, the exact proportions of which the study was unable to verify. Previously, Wax et al. had surmised from the available evidence that the Moscow emergency services had not been informed of the use of the agent, but were instructed to bring opioid antagonists. Because of the lack of information provided, the emergency workers did not bring adequate supplies of naloxone (opioid inverse agonist) or naltrexone (opioid antagonist) to prevent complications in many of the victims and there were subsequently over 125 confirmed casualties from both respiratory failure and aerosol inhalation during the incident. Assuming that carfentanil and remifentanil were the only active constituents (which has not been verified by the Russian military), the primary acute toxic effect to the theatre victims would have been opioid-induced apnea; in this case mechanical ventilation and/or treatment with opioid antagonists would have been life-saving for many or all victims.
A practical example of the drug in use in veterinary practice was shown in an episode of the Discovery Channel series, Animal Cops: Houston, where carfentanil was administered orally dissolved in honey to a full-grown brown bear to tranquilize it so that it could be safely relocated to the Houston Zoo from a south Texas animal abuser's property. A similar drug was also used in the science fiction film The Lost World: Jurassic Park, having been used to capture a Tyrannosaurus rex.
See also 
- ^ Stanley TH, Egan TD, Van Aken H (2008). "A Tribute to Dr. Paul A. J. Janssen: Entrepreneur Extraordinaire, Innovative Scientist, and Significant Contributor to Anesthesiology". Anesth Analg 106 (2): 451–62. doi:10.1213/ane.0b013e3181605. PMID 18227300. Retrieved 2011-05-07.
- ^ Fentanyl#Non-pharmaceutical fentanyls
- ^ De Vos V (1978). "Immobilisation of free-ranging wild animals using a new drug". The Veterinary Record 103 (4): 64–8. doi:10.1136/vr.103.4.64. PMID 685103. Retrieved 2010-09-27.
- ^ Riches JR, Read RW, Black RM, Cooper NJ, Timperley CM. Analysis of Clothing and Urine from Moscow Theatre Siege Casualties Reveals Carfentanil and Remifentanil Use. J Anal Toxicol. 2012 Sep 20. (Epub ahead of print). Riches, J. R.; Read, R. W.; Black, R. M.; Cooper, N. J.; Timperley, C. M. (2012). "Analysis of Clothing and Urine from Moscow Theatre Siege Casualties Reveals Carfentanil and Remifentanil Use". Journal of Analytical Toxicology 36 (9): 647–656. doi:10.1093/jat/bks078. PMID 23002178..
- ^ Wax PM, Becker CE, Curry SC. Unexpected "gas" casualties in Moscow: a medical toxicology perspective. Ann Emerg Med 2003;41:700–5. Wax, P. M.; Becker, C. E.; Curry, S. C. (2003). "Unexpected "gas" casualties in Moscow: A medical toxicology perspective". Annals of Emergency Medicine 41 (5): 700–705. doi:10.1067/mem.2003.148. PMID 12712038..