Hi S. -
Hand, Foot & Mouth disease (also known as Coxsackie Virus) cannot be treated with an antibiotic, since it is a viral infection. That being said, there is a concoction that my doctor prescribed when my son Pete (now nearly 15 months old) contracted the virus about a month ago: it contains Benedryl, Maalox and Lidocaine (which is a topical anesthetic/analgesic, it basically numbs the pain). You need to get a prescription for it, so call your doctor. It's not a miracle cure, but it helps them temporarily and is better than nothing. You swab this on the inside of the mouth to help numb the pain of the sores; in addition, you can alternate giving your daughter Infant Motrin and Tylenol to maintain a steady level of pain management - these drugs do not interact with one another; just follow the directions your doctor gives you. Pete's doctor had us giving him infant Motrin in the morning, then Tylenol a few hours later, then the Motrin (at the proper interval - 6 hours later, I think), then Tylenol, etc. It helped keep Pete more comfortable and his fever down.
A couple of things to note about Coxsackie Virus - not all kids show symptoms of it, but all are exposed to it. It is very common, and can run rampant through day care centers, but not everyone is aware when their child is exposed to it, since some people only have a sore throat. Once you are exposed to one strain, you are immune (you may come down with another strain, however). Coxsackie is highly contagious, but is generally not seen in adults (since chances are, we've already been exposed to it); you want to make sure to keep her away from other children (and out of day care) until she has been fever-free for at least 24 or 48 hours. Your daughter may develop a red pinpoint rash on her hands and feet; this is normal. If you get the concoction I described above, try giving your daughter Pedialyte right after swabbing her mouth, to try to minimize the risk of dehydration. You can mix it with apple or grape juice, but try to avoid acidic fruit juices since they will sting her mouth. Milk is also good, and will hurt less. My son didn't drink anything for an entire day - once we swabbed his mouth, he sucked down his bottle and had some Pedialyte and apple juice.
Call your doctor, ask about the concoction, and check on the Motrin/Tylenol schedule. Pete's virus lasted about 5 days. Good luck - hope that Amber is feeling better soon!
B.