From the Guidelines
Azithromycin is the recommended first-line treatment for dysentery due to its high efficacy and favorable pharmacokinetic properties, with a single 1-gm dose or 500 mg daily for 3 days being the preferred regimen. The pharmacokinetics of azithromycin, including its rapid absorption, high tissue concentration, and long half-life, allow for once-daily dosing and make it an effective treatment for bacterial dysentery 1. In contrast, fluoroquinolones (FQs) such as ciprofloxacin and levofloxacin, which were previously considered first-line treatments, have shown reduced efficacy due to increasing resistance rates, particularly in Southeast Asia and India 1. Rifaximin, a nonabsorbable antibiotic, has demonstrated comparable efficacy to FQs in non-invasive TD caused by diarrheagenic E. coli, but is less effective for the treatment of invasive pathogens 1.
Some key points to consider when selecting an antibiotic for the treatment of dysentery include:
- The likelihood of treatment efficacy and rapidity of response
- Regional patterns of probable target pathogens and their antimicrobial resistance
- Safety and tolerance profile of the antibiotic
- Simplicity of treatment regimen and patient adherence
- Cost
Azithromycin has been shown to be superior to levofloxacin in achieving clinical cure in Thailand, where FQ-resistant Campylobacter spp. are prevalent 1. Additionally, azithromycin has demonstrated effective and comparable cure rates with shigellosis, another common agent causing dysentery 1. The pharmacokinetic properties of azithromycin, including its high tissue concentration and long half-life, allow for once-daily dosing and make it an effective treatment for bacterial dysentery.
In terms of dosing, azithromycin 500 mg once daily for 3 days or a single 1-gm dose is recommended, with the option to split the single dose over the first day to minimize side effects 1. It is essential to note that patients should complete the full course of antibiotics even after symptom improvement to prevent relapse and antimicrobial resistance. Symptomatic relief medications like loperamide can be used in conjunction with antibiotics to manage symptoms, but should not be used as a substitute for antibiotic treatment in cases of dysentery.
From the FDA Drug Label
The first study consisted of 35 pediatric patients treated with 20 mg/kg/day (maximum daily dose 500 mg) for 3 days of whom 34 patients were evaluated for pharmacokinetics. In the second study, 33 pediatric patients received doses of 12 mg/kg/day (maximum daily dose 500 mg) for 5 days of whom 31 patients were evaluated for pharmacokinetics The following table shows pharmacokinetic data in the subset of pediatric patients who received a total dose of 60 mg/kg. Pharmacokinetic Parameter [mean (SD)] 3-Day Regimen (20 mg/kg × 3 days) 5-Day Regimen (12 mg/kg × 5 days) n 11 17 Cmax (mcg/mL) 1.1 (0.4) 0.5 (0.4) Tmax (hr) 2.7 (1.9) 2.2 (0.8) AUC0–24(mcg∙hr/mL) 7.9 (2.9) 3.9 (1. 9)
The pharmacokinetics of azithromycin in pediatric patients are characterized by:
- Cmax: 1.1 mcg/mL (3-day regimen) and 0.5 mcg/mL (5-day regimen)
- Tmax: 2.7 hours (3-day regimen) and 2.2 hours (5-day regimen)
- AUC0-24: 7.9 mcg∙hr/mL (3-day regimen) and 3.9 mcg∙hr/mL (5-day regimen) 2