Hot Dog, extra large?

Turning a corner, you both encounter the werewolf again. He has a bandaged foot and limps.

"You may have beaten me last time" he says, producing a potion. "but now you're the one that's getting burnt! One swig of this potion will turn me into a fire-breathing dragon, and then you're gonna get it!"

And with that, he downs the entire bottle, something you don't think he should have done...