Does your baby have thrush? When my son had thrush he was prescribed some drops. Not sure what the medicine was. I don't think I ever had thrush ... it's been too long. Maybe my OB prescribed a cream? I can't remember.
Ziggy is right, though. Thrush is a yeast infection, so antibiotics would not be prescribed. But antibiotics could cause thrush. Have you ever gotten a yeast infection (and this time I mean vaginal) after taking antibiotics? I have. My husband said, "Forget to eat your yogurt?"
I've heard of people using yogurt to treat a yeast infection. I'm more of a modern medicine person myself, so I prefer Monostat or a prescription. But I will eat lots of yogurt while taking antibiotics to hopefully prevent a yeast infection.
Good luck! Hope you and/or baby get better soon!