Our baytril/doxy/zithro is always in pill (powder for the zithro) form, which we compound here - it's much cheaper for the amount of rats we're treating at any given time.
They may have made the doxy into a compound, but I'm not so sure why they'd mix it with baytril. I know my vet will give owners pre-compounded (at the time you're at the vet), I guess you could call it, of baytril and/or doxy but never combined in a syringe. It's always 1 syringe per drug.
I know they do it because it's easier for some owners to give an already pre-filled amount, but I just don't know why they'd combine two meds into one. I don't know if that changes anything or not.