Ok, the antibiotic's trade name is Flagyl which is pretty commonly used. It mainly treats anaerobic bacteria incuding Clostridium,a dangerous one common to upset rabbit intestines. Which are rod-shaped, which is what Dr. Bixler said she saw in the fecal smear.
Hopefully the toxins from Clostridium haven't had time to build up much, especially with the diarrhea moving stuff out quickly.
The other drug is the standard Coccidea treatment.