If exposure is suspected, the person should be removed from the source of exposure and decontaminated. Treatment involves supportive care and giving the person 100% oxygen. Hydroxocobalamin (vitamin B12) appears to be useful as an antidote and is generally first-line. Sodium thiosulphate may also be given. Historically cyanide has been used for mass suicide and by the Nazis for genocide.

is oxygen an effective treatment for cyanide poisoning?
yes