What is the drug of choice for treating dysentery?

Drug of Choice for Dysentery

Azithromycin is the drug of choice for dysentery, with a recommended dose of 1000 mg as a single dose or 500 mg daily for 3 days. 1, 2

First-Line Treatment Recommendation

Azithromycin should be the preferred agent for all cases of dysentery (bloody diarrhea with mucus or pus), regardless of geographic region. 2, 3 This recommendation is based on:

• Superior efficacy against the most common dysentery pathogens (Shigella species and Campylobacter), with studies showing 100% clinical and bacteriological cure rates 2
• Excellent safety profile compared to fluoroquinolones, which carry black box warnings for tendon rupture, C. difficile infection, and QT prolongation 1, 2
• Global fluoroquinolone resistance patterns that now exceed 85% for Campylobacter in Southeast Asia and are increasing worldwide 3

Dosing Regimens

For adults with dysentery: 1, 2

• Single 1000 mg dose (preferred for compliance), OR
• 500 mg daily for 3 days

For children: 1

• 30 mg/kg/day for 5 days (based on older guidelines, though newer evidence supports adult-equivalent dosing)

Alternative Agents When Azithromycin Is Not Available

Ciprofloxacin (Second-Line)

Ciprofloxacin remains an option in regions with documented low fluoroquinolone resistance, but should not be first-line due to increasing resistance and safety concerns. 1

• Adults: 500 mg twice daily for 3 days, or 750 mg single dose 1, 4
• Children: 15 mg/kg/day (though associated with arthropathy risk) 1
• Critical limitation: Resistance rates to ciprofloxacin now reach 5.0% in Asia-Africa and are progressively increasing, with even higher rates in children than adults 1

Cefixime or Ceftriaxone (Third-Line)

Oral cefixime or parenteral ceftriaxone are appropriate alternatives when azithromycin and fluoroquinolones have failed or resistance is documented. 1

• Resistance rates to ceftriaxone remain relatively low (2.5% in Asia-Africa, 0.4% in Europe-America) 1
• Particularly useful for severe cases requiring hospitalization 1

Historical Context: Older Regimens No Longer Recommended

The 1992 guidelines recommended ampicillin or TMP-SMX as first-line agents 1, but these are now obsolete due to widespread multidrug resistance. 1 Resistance rates to ampicillin and cotrimoxazole are now extremely high globally, making them ineffective for empiric therapy. 1, 5

Critical Diagnostic Considerations

Before treating for dysentery, attempt to distinguish bacterial from amebic causes when possible: 1, 6

• Microscopic examination of fresh stool should be performed to identify Entamoeba histolytica trophozoites 1, 6
• Amebic dysentery is frequently misdiagnosed and tends to be overdiagnosed 6
• If microscopy is unavailable or negative for amoeba, treat empirically for bacterial dysentery (Shigella) first 1, 6
• Only consider amebic treatment if: microscopy shows definite trophozoites OR two different antibiotics for shigellosis have failed 1, 6

Treatment for Confirmed Amebic Dysentery

Metronidazole 750 mg orally three times daily for 5-10 days (adults) or 30 mg/kg/day for 5-10 days (children) 1, 6

• Must be followed by a luminal amebicide (diloxanide furoate 500 mg three times daily for 10 days or paromomycin 30 mg/kg/day in 3 divided doses for 10 days) to prevent relapse 6

Common Pitfalls to Avoid

1. Do not use rifaximin for dysentery - it has documented treatment failures in up to 50% of cases with invasive pathogens and is only appropriate for non-invasive watery diarrhea 1, 3

2. Do not delay antibiotic change if no clinical response within 48 hours - switch to an alternative agent rather than continuing ineffective therapy 1

3. Do not use antimotility agents (loperamide) in dysentery - these are contraindicated in bloody diarrhea as they may worsen invasive disease 7

4. Do not assume fluoroquinolones are still universally effective - regional resistance patterns must guide therapy, and azithromycin is now preferred globally 1, 2

5. Do not treat presumed amebiasis without microscopic confirmation or documented antibiotic failure - this leads to inappropriate treatment and delays proper bacterial dysentery management 1, 6

Adjunctive Therapy

Oral rehydration solution should be given concurrently to prevent or correct dehydration 1, 7

Feeding should continue during and after illness to maintain nutritional status 7