Moscow hostage crisis chemical agent

The chemical agent used in the Moscow theatre hostage crisis of 23 October 2002 has never been definitively revealed by the Russian authorities, though many possible identities have been speculated. An undisclosed incapacitating agent was used by the Russian authorities in order to subdue the Chechen terrorists who had taken control of a crowded theater.

At the time, the agent was surmised to be some sort of surgical anesthetic or chemical weapon. Immediately after the siege, Western media speculated widely as to the identity of the substance that was used to end the siege, and chemicals such as the tranquilizer diazepam (Valium), the anticholinergic BZ, the highly potent oripavine-derived Bentley-series opioid etorphine, another highly potent opioid, such as a fentanyl or an analogue thereof, such as 3-methylfentanil, and the anaesthetic halothane were proposed. Foreign embassies in Moscow issued official requests for more information on the gas to aid in treatment, but were publicly ignored. While still refusing to identify the gas, on October 28, 2002 the Russian government informed the U.S. Embassy of some of the gas's effects. Based on this information and examinations of victims, doctors concluded the gas was a morphine derivative. The Russian media reported the drug was Kolokol-1, either mefentanyl or α-methylfentanil dissolved in a halothane base.

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