Flagyl is available in doses for adults as tablets of 250 mg, 500 mg, and 750 mg. The dose for pediatric patients is available as tablets of 35 to 50 mg/kg/24 hours. Patient dosage administration depends upon the severity of infection caused by parasites or bacteria, and any other existing medical conditions, particularly if they are severe. There are several drug interactions with Flagyl. Interactions, for example, like warfarin (Coumadin, Jantoven), cimetidine (Tagamet), cholestyramine (Questran, Questran Light), amprenavir (Agenerase), lithium (Eskalith, Lithobid), and cyclosporine. This medicine may cause increased heart rate, which can lead to seizures. Ask your doctor, pharmacist, or other medical professional if you have questions about Flagyl.