Has anyone here used melatonin on their LO?

Not looking for arguments against it - we've tried everything at this point and the two nights she had it (in Zarbee's) she slept til 5:15 and then 6 am. That is UNHEARD of here! I bought the Zarbee's gentle sleep melatonin and I plan to give it a shot to at least try to reset her sleep schedule.