No, they are not, and have never been. NASA has never issued its astronauts anyf orm of lethal pill or capsule. The need is simply not there, as Jim Lovell, commander of the Apollo 13 mission explained. Many asked him if he and the other crewmen onboard Apollo 13 had been issued these pills for use in a scenario like what crippled the missions command module and nearly doomed the astronauts. He and other astronauts all discounted the idea NASA ever issued them. In fact, he went further to explain it is totally unecessary: If faced with no hope of rescue, the Apollo 13 astronauts could have opened the command module up and depressurise it near instantly, allowing the vaccuum of space to kill them. However, there are some claims that Soviet cosmonauts were issued them on rare occaisons: Alexei Leond, first man to walk in space, reveealed he was issued a lethal tablet to swallow in the event he could not be recovered into the Voshkod 2 spacecraft and had to be cut loose. However I can find little evidence to suggest these were ever standard issue, or even issued at all outside of Leonod and Belyayev's Voshkod 2 mission.