tl;dr: This was banned by other countries because of other chemicals causing poisoning issues, not because this one did. The changes this chemical causes when directly injested is fat reduction, reduced hunger, and muscle retention, along with behavioral agitation and aggression increases.

It's 'safe' because the FDA looked at research saying that it does not remain in animal muscle tissues (meat) for more than 24 hours as it's rapidly broken down and not because they looked at research and said it was safe for human consumption.