A 38-year-old man from rural Bihar presents with bloody diarrhea and abdominal pain for 2 weeks. Stool microscopy reveals trophozoites of Entamoeba histolytica with ingested RBCs. He has no evidence of liver abscess on ultrasound. What is the drug of choice for treating his intestinal amoebiasis?

Explanation

## Treatment of Invasive Intestinal Amoebiasis **Key Point:** For **symptomatic invasive intestinal amoebiasis** (amoebic dysentery with trophozoites ingesting RBCs), the **drug of choice is Metronidazole** — a tissue-acting nitroimidazole that kills invasive trophozoites in the intestinal wall and systemic tissues. ### Drug Classification in Amoebiasis | Drug | Site of Action | Indication | Notes | |------|---|---|---| | **Metronidazole** | **Tissue (trophozoites)** | **Invasive intestinal amoebiasis, liver abscess** | **Drug of choice for symptomatic/invasive disease** | | Diloxanide furoate | Luminal (intestinal lumen) | Asymptomatic cyst passers; follow-up after metronidazole | Does NOT treat invasive disease | | Chloroquine | Liver tissue | Hepatic amoebiasis (second-line) | Not effective for intestinal disease | | Tetracycline | Luminal | Alternative luminal agent (rarely used) | Less effective; not first-line | ### Correct Approach to This Case This patient has **invasive intestinal amoebiasis** — bloody diarrhea, abdominal pain, and trophozoites with ingested RBCs on stool microscopy. The standard treatment is: 1. **Metronidazole 750 mg TDS × 10 days** — eliminates invasive trophozoites (tissue phase) 2. **Followed by Diloxanide furoate 500 mg TDS × 10 days** — eliminates residual luminal cysts to prevent relapse **High-Yield:** The question asks for the **drug of choice for intestinal amoebiasis** in a symptomatic patient with dysentery. Per KD Tripathi (*Essentials of Medical Pharmacology*, 8th ed.) and Harrison's Principles of Internal Medicine, **Metronidazole is the drug of choice for invasive/symptomatic amoebiasis**. Diloxanide furoate is the drug of choice only for **asymptomatic cyst passers** — it has no role as monotherapy in invasive disease. **Clinical Pearl:** Metronidazole alone does not reliably eliminate luminal cysts, so it must be followed by a luminal agent (diloxanide furoate or paromomycin). However, when asked for the "drug of choice" for symptomatic invasive intestinal amoebiasis, the answer is always **Metronidazole**. **Mnemonic:** **Metro = Invasive disease** (Metronidazole for tissue trophozoites); **Diloxanide = Luminal/Cyst phase** (asymptomatic carriers)