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Kolokol-1 (Russian: Колокол meaning "bell") is a synthetic opioid developed for use as an aerosolizable incapacitating agent. Although the exact chemical structure has not yet been revealed, it is thought to be a derivative of the potent opioid fentanyl, most probably 3-methylfentanyl dissolved in halothane as an organic solvent.[1]

Chemical structure and physiologic effects[edit]

Experts point to 3-methylfentanyl[2][3] as the likely agent, since the drug is formulated to be delivered as an aerosol. However while Russian authorities initially hinted that 3-methylfentanyl was the active opioid agent in Kolokol-1, forensic analysis of the clothing and urine of hostages showed traces of other potent opioids instead, namely carfentanil and remifentanil.[4]

Upon inhalation or exposure through the skin, Kolokol-1 takes effect within 10-30 seconds, rendering the subject unconscious for two to six hours. In humans, the drug produces hypoventilation, which may progress to apnea, the severity being dependant on the level of exposure and the subject's degree of opioid tolerance. Hypoventilation may lead to death if the subject is not provided with ventilatory assistance; apnea, the complete cessation of breathing, is naturally fatal.

Development and early use[edit]

According to Lev Fyodorov, a former Soviet chemical weapons scientist who now heads the independent Council for Chemical Security in Moscow, the agent was originally developed around a secret military research facility in Saint Petersburg, then known as Leningrad, during the 1970s. Methods of dispersing the compound were reportedly developed and tested by releasing harmless bacteria through subway system ventilation shafts first in the Moscow and then in Novosibirsk. Fyodorov also claimed that leaders of the failed August 20, 1991 Communist coup considered using the agent in the Russian parliament building.[5]

Use during Moscow theater hostage crisis[edit]

Kolokol-1 is thought to be the chemical agent employed by a Russian Spetsnaz team during the Moscow theater hostage crisis in October 2002. At least 129 hostages died during the ensuing raid; nearly all of these fatalities were attributed to the effects of the aerosolised incapacitating agent that was pumped into the theatre to subdue the militants.[6][7]


  1. ^ Russia Confirms Suspicions About Gas Used in Raid, Washington Post, 31 October 2002.
  2. ^ Page 301 Pharmacology for Anesthetists - By John D. Current, M.D
  3. ^ Page 226 Basic Principles of Forensic Chemistry By JaVed I. Khan, Donnell R. Christian, Jr., Thomas J. Kennedy
  4. ^ Riches J, Read R, Black R, Cooper N, and Timperley C. Analysis of clothing and urine from Moscow theatre siege casualties reveals carfentanil and remifentanil use. Journal of Analytical Technology. 2012; 36: 647–656.
  5. ^ Gas looks like secret KGB tool, New York Daily News, 29 October 2002
  6. ^ Gas 'killed Moscow hostages', BBC News, 27 October 2002
  7. ^ Moscow court begins siege claims, BBC News, 24 December 2002