oral thrush
"My father, a brain tumor patient, had oral thrush, which is very common for those taking long-term Dilantin. This swish-and-swallow medication worked wonders for him, within about 3 days. Be sure to take it for the full prescription period, usually 14 days. Also, the longer you can hold the gargle, the longer the contact between drug and organisms. Thrush can also move from the mouth into the throat, and it can recur quickly, so out of sight doesn't necessarily mean anything. Again, take it for the full period recommended by the doctor."