What is the recommended metronidazole dosage for an otherwise healthy adult with acute dysentery caused by Entamoeba histolytica?

Metronidazole Dosing for Acute Amebic Dysentery

For an otherwise healthy adult with acute dysentery caused by Entamoeba histolytica, administer metronidazole 750 mg orally three times daily for 5–10 days, followed by a luminal amoebicide to prevent relapse. 1

Standard Treatment Regimen

Acute Intestinal Amebiasis (Acute Amebic Dysentery)

• Metronidazole dose: 750 mg orally three times daily for 5–10 days in adults 1
• This FDA-approved regimen achieves cure rates exceeding 90% for invasive disease 2
• The 750 mg three-times-daily dosing is superior to lower doses for symptomatic intestinal amebiasis 3

Essential Follow-Up: Luminal Amoebicide

• After completing metronidazole, all patients must receive a luminal amoebicide (such as diloxanide furoate 500 mg three times daily for 10 days or paromomycin) to eradicate intestinal cysts and prevent relapse 2
• Metronidazole alone does not eliminate luminal cysts, even when stool microscopy becomes negative 2, 4
• Omitting luminal therapy is a critical pitfall that leads to treatment failure and recurrence 2

Alternative Dosing for Amebic Liver Abscess

• If the patient develops amebic liver abscess (not acute dysentery), use metronidazole 500–750 mg orally three times daily for 7–10 days 1, 2
• The same requirement for subsequent luminal amoebicide therapy applies 2

Pediatric Dosing

• For children with acute amebic dysentery: 35–50 mg/kg/24 hours divided into three oral doses for 10 days 1

Critical Safety Considerations

Neurotoxicity Warning

• Avoid repeated or prolonged courses beyond 14 days due to cumulative and potentially irreversible neurotoxicity 5, 2
• Monitor closely for peripheral neuropathy, seizures, or other neurological symptoms during treatment 2

Alcohol Restriction

• Patients must avoid alcohol during therapy and for 24 hours after the last dose because of disulfiram-like reactions 5, 2

Special Populations

Pregnancy

• Do not treat during the first trimester 1
• If treatment is required in later pregnancy, use the lower dose of 250 mg three times daily for 7 days to minimize fetal exposure 2
• Avoid the single-dose regimen in pregnancy as it produces higher serum levels that reach fetal circulation 1

Hepatic Impairment

• Patients with severe hepatic disease metabolize metronidazole slowly, leading to drug accumulation 1
• Administer doses below usual recommendations cautiously and monitor plasma levels 1

Common Pitfalls to Avoid

• Do not omit luminal amoebicide therapy after metronidazole—this is the most common cause of treatment failure 2
• Do not use metronidazole for routine bacterial gastroenteritis without confirmed protozoal infection 2
• Do not prescribe courses longer than 14 days without compelling indication due to neurotoxicity risk 5, 2
• Do not use lower doses (e.g., 500 mg three times daily) for acute amebic dysentery, as the 750 mg dose is FDA-approved and more effective 1