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.[4][5] 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.