What is the standard treatment regimen for intestinal amoebiasis (Entamoeba histolytica), including tissue‑active and luminal agents, dosing, and special considerations for pregnancy and children?

Treatment of Intestinal Amoebiasis

For intestinal amoebiasis caused by Entamoeba histolytica, treat with metronidazole 750 mg orally three times daily for 5-10 days (or 35-50 mg/kg/day divided into three doses for children), followed immediately by a luminal amebicide such as paromomycin 25-35 mg/kg/day in three divided doses for 5-10 days to eliminate intestinal cysts and prevent relapse. 1, 2, 3

Standard Two-Phase Treatment Approach

Phase 1: Tissue-Active Agent (Treat Invasive Disease)

Metronidazole is the drug of choice for symptomatic intestinal amebiasis:

• Adults: 750 mg orally three times daily for 5-10 days 4, 1, 2
• Children: 30 mg/kg/day (or 35-50 mg/kg/24 hours) divided into three doses for 10 days 4, 2
• Achieves approximately 88% parasitological cure when followed by luminal amebicide 1

Phase 2: Luminal Amebicide (Eliminate Intestinal Cysts - MANDATORY)

After completing metronidazole, ALL patients must receive a luminal amebicide to prevent relapse, even if stool microscopy becomes negative: 1

• Paromomycin (preferred): 25-35 mg/kg/day in three divided doses with meals for 5-10 days (adults and children) 3, 5
• Alternative - Diloxanide furoate: 500 mg three times daily for 10 days (adults) 1

Critical pitfall: Failure to complete the luminal amebicide phase results in persistent intestinal colonization and high relapse rates, as metronidazole alone achieves only 44% cure versus 91% when combined with luminal agents 6

Special Populations

Pregnancy

• Metronidazole is contraindicated in the first trimester 2
• For pregnant patients requiring treatment after first trimester, use the standard 750 mg three times daily regimen (NOT the single-dose regimen, as it produces higher fetal drug exposure) 2
• Amphotericin B formulations are safe alternatives during pregnancy for severe cases, though this applies more to systemic fungal infections based on available evidence 4

Children

• Metronidazole: 35-50 mg/kg/24 hours divided into three doses for 10 days 2
• Paromomycin: Same weight-based dosing as adults (25-35 mg/kg/day in three divided doses) 3
• The pediatric regimen is well-tolerated and effective 4

Monitoring and Follow-Up

• Stool examination should be performed at least 14 days after completing BOTH treatment phases to confirm parasite elimination 1
• For hepatic involvement, follow-up ultrasound may be necessary to confirm resolution 1
• If repeat courses are required, allow 4-6 weeks between courses with reconfirmation of trichomonad presence and complete blood counts 2

Important Clinical Considerations

Dosing Adjustments

• Severe hepatic disease: Reduce doses below standard recommendations due to drug accumulation; monitor plasma levels closely 2
• Elderly patients: Pharmacokinetics may be altered; consider monitoring serum levels 2
• Renal failure: No specific dose reduction needed in anuric patients, as metabolites are rapidly removed by dialysis 2

Common Pitfalls to Avoid

1. Omitting the luminal amebicide phase - This is the most critical error, resulting in treatment failure rates exceeding 50% 6
2. Treating presumptively without confirmation - Only treat after microscopic identification of trophozoites or positive antigen/PCR testing 4, 7
3. Alcohol consumption during treatment - Patients must abstain from alcohol during metronidazole therapy and for 24 hours after completion to avoid disulfiram-like reactions 8
4. Failing to treat sexual partners - All sexual contacts should receive treatment to prevent reinfection 8

Adverse Effects of Paromomycin

• Diarrhea occurs in approximately 13.8% of patients but resolves after treatment completion 5
• Other gastrointestinal symptoms affect 18.7% of patients overall 5
• Generally safe and well-tolerated, including in HIV-infected individuals 5

Maximum Dosing Limits

• Metronidazole: Maximum 4 grams per 24-hour period 2
• Treatment duration typically 7-10 days for most serious infections; bone, joint, and endocardial infections may require longer courses 2