Suicide pill

A suicide pill (also known as the cyanide pill, kill-pill, lethal pill, death-pill, or L-pill) is a pill, capsule, ampoule, or tablet containing a fatally poisonous substance that one ingests deliberately in order to quickly achieve death through suicide. Military and espionage organisations have provided their agents in danger of being captured by the enemy with suicide pills and devices which can be used in order to avoid an imminent and far more unpleasant death (such as through torture), or to ensure that they cannot be interrogated and forced to disclose secret information. As a result, lethal pills have important psychological value to persons carrying out missions with a high risk of capture and interrogation.
The term "poison pill" is also used colloquially for a policy or legal action set up by an institution that has fatal or highly unpleasant consequences for that institution if a certain event occurs. Examples are the poison pill shareholders rights amendments inserted in corporate charters as a takeover defence, and wrecking amendments added to legislative bills.
Description.
During World War II, British and American secret services developed the "L-pill" (lethal pill) which was given to agents going behind enemy lines. It was an oval capsule, approximately the size of a pea, consisting of a thin-walled glass ampoule covered in brown rubber to protect against accidental breakage and filled with a concentrated solution of potassium cyanide. It could be carried in the mouth, shaped as a false tooth; if it was accidentally swallowed it would pass harmlessly through the body. To use, the agent would bite down on the pill, crushing the ampoule to release the fast-acting poison. Heartbeat quickly stops and brain death occurs within minutes. 
After the war, the L-pill was offered to pilots of the U-2 reconnaissance plane, who were in danger of being shot down and captured flying over Eastern Europe, but most pilots declined to take it with them.
The Central Intelligence Agency began experimenting with saxitoxin, an extremely potent neurotoxin, during the 1950s as a replacement for the L-pill. According to CIA Director William Colby, a tiny saxitoxin-impregnated needle hidden inside a fake silver dollar was issued to Francis Gary Powers, an American U-2 pilot who was shot down while flying over the USSR in May 1960.
According to Former CIA Chief of Disguise Jonna Mendez, the CIA hid poison pills in a number of items, including the caps of pens, and the frames of glasses. Operatives would bite down, and the poison concealed inside would be released.
Metaphorical uses.
In economics, a suicide pill is a form of risk arbitrage used by corporations to suicide during hostile takeover attempts. As an extreme version of the poison pill defense, this crippling provision refers to any technique used by a target firm in which takeover protection could result in self-destruction.
Variations of the suicide pill include the Jonestown Defense, the Scorched Earth defense, and the golden parachute.
Space travel.
One urban legend suggests that American astronauts could carry suicide pills in case they are unable to return to Earth. It is possible this myth was started by the movie "Contact" in a scene where the main character is given suicide pills in case she cannot get back to Earth. This was disputed by astronaut Jim Lovell, who co-wrote "Lost Moon" (later renamed "Apollo 13"). On the DVD director's commentary, it was asserted that because marooned astronauts could easily commit suicide by simply venting the air from their spacecraft or suits, such a pill would not likely be necessary.
Cosmonaut Alexei Leonov stated that the Soviet space program gave him a suicide pill for use if he could not reenter Voskhod 2 after his March 1965 spacewalk.