A patient present with lower gastrointestinal bleed. Sigmoidoscopy shows ulcers in the sigmoid. Biopsy from this area shows flask-shaped ulcers. Which of the following is the most appropriate treatment -

Typical flask shaped ulcers are seen in amoebiasis. Intestinal & early hepatic amoebiasis responds quickly to oral metronidazole (800mg 3times daily for 5-10 days) or other long acting nitroimidazoles like tinidazole or ornidazole. In severe cases of amoebic dysentery or liver abscess 500mg may be infused i.v. slowly every 6-8 hrs for 7-10 days or till oral therapy is instituted . Reference: Harrison20th edition pg 1207