Azithromycin Dosing for Dysentery

For dysentery (bloody diarrhea), azithromycin should be dosed at 1000 mg as a single oral dose, or alternatively 500 mg daily for 3 days. 1, 2, 3

Preferred Dosing Regimen

The single 1000 mg dose is the preferred regimen because it offers equivalent efficacy to the 3-day course while providing superior adherence and convenience. 2, 4
The alternative 3-day regimen (500 mg daily for 3 days) is equally effective if the single dose is not tolerated or available. 1, 4

Azithromycin is the preferred first-line antibiotic for dysentery regardless of geographic region because it provides superior coverage against the most common invasive pathogens causing bloody diarrhea. 1, 2, 5
For Shigella infections (the most common cause of dysentery), azithromycin demonstrates effective cure rates and should be used as first-line treatment. 2, 4
For Campylobacter infections, azithromycin achieves 100% clinical and bacteriological cure rates, far superior to fluoroquinolones which have documented treatment failures. 1, 2, 4
Fluoroquinolone resistance among Campylobacter species now exceeds 85-90% in Southeast Asia and is widespread globally, making azithromycin clearly superior. 1, 4

In Southeast Asia and India, azithromycin should be the default empiric agent for any dysentery due to extremely high fluoroquinolone resistance rates (78-93% for Campylobacter). 1, 4
Even in other geographic regions, azithromycin remains preferred for dysentery because invasive pathogens are likely. 1, 2

For severe dysentery that is incapacitating or when oral intake is not tolerated, IV azithromycin 500 mg daily for 2-5 days is recommended, followed by transition to oral therapy when tolerated. 2
Continue IV therapy until clinical improvement occurs, typically 2-5 days. 2

Azithromycin can be combined with loperamide (4 mg initial dose, then 2 mg after each loose stool, maximum 16 mg/24 hours) for faster symptomatic relief, reducing time to last unformed stool to less than 12 hours. 2, 4
However, loperamide should be discontinued if symptoms worsen or dysentery persists, as continued use in the face of worsening invasive disease is cautioned. 1

Do not use rifaximin for dysentery - it has documented treatment failures in up to 50% of cases with invasive pathogens and should specifically not be prescribed when Campylobacter, Shigella, or other invasive organisms are suspected. 1, 2
Do not use fluoroquinolones (ciprofloxacin, levofloxacin) as first-line for dysentery - they are inferior to azithromycin for Shigella and have high failure rates for fluoroquinolone-resistant Campylobacter. 1, 5, 3
Do not administer azithromycin simultaneously with aluminum or magnesium-containing antacids as they significantly reduce absorption. 2, 5
Do not use co-trimoxazole, ampicillin, or erythromycin due to widespread resistance that compromises efficacy. 5

If no clinical response occurs within 48 hours of azithromycin therapy, consider resistant Shigella or alternative diagnoses (including amebiasis if microscopy shows Entamoeba histolytica trophozoites). 1
Stool microscopy and culture should be obtained when possible, though empiric therapy with azithromycin is warranted in severe dysentery cases. 5

While azithromycin resistance in Shigella species is emerging in some regions (up to 25.5% resistance reported in one Iranian study), it remains significantly lower than resistance to other commonly used antibiotics like ceftriaxone (43.6%) and co-trimoxazole (82.9%). 6
Despite this emerging resistance, azithromycin remains the best available empiric option for dysentery based on overall efficacy and resistance patterns. 2, 5