How does a cyanide pill kill you?

[Enola_Straight]

We’ve all seen in the movies and tv how a secret agent, when about to be captured, bites a cyanide pill and immediately dies, preventing interrogation.

Just how does it work?

need the answer fast.

[beowulff]

In about 5 minutes, and very painfully.
I would imagine it feels like being suffocated.

Millionaire Arsonist Who Died in Courtroom Had Canister Labeled 'Cyanide' in...

[Wesley_Clark]

It blocks the cytochrome c oxidase enzyme from working.

[John_DiFool]

The movie Downfall showed Madame Goebbels poisoning her own children, where they appeared to expire very quickly and painlessly.

[mbh]

Cyanide poisoning

Cyanide poisoning is a form of histotoxic hypoxia because the cells of an organism are unable to use oxygen, primarily through the inhibition of cytochrome c oxidase. Acute hydrogen cyanide poisoning can result from inhalation of fumes from burning polymer products that use Nitrile in their production, such as polyurethane, or vinyl.[1] If cyanide is inhaled it causes a coma with seizures, apnea, and cardiac arrest, with death following in a matter of seconds. At lower doses, loss of consciousness may be preceded by general weakness, giddiness, headaches, vertigo, confusion, and perceived difficulty in breathing. At the first stages of unconsciousness, breathing is often sufficient or even rapid, although the state of the victim progresses towards a deep coma, sometimes accompanied by pulmonary edema, and finally cardiac arrest. A cherry red skin color that changes to dark may be present as the result of increased venous hemoglobin oxygen saturation.