From Halopedia, the Halo wiki
Polypseudomorphine, colloquially known as polly-sue, is a sedative used by the United Nations Space Command. Enough polypseudomorphine can keep an adult human sedated for the better part of a day. A small injection of the drug can also be used to ease one's pain. The Spartan-II Blue Team used polypseudomorphine to sedate Colonel Robert Watts so he could be brought back to the Office of Naval Intelligence for interrogation. The Rookie used the drug to ease the pain of the dying Gage Yevgenny.
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