However, certain patients, including the following, should usually be treated: Children Older people Debilitated patients Patients with moderate to severe disease For adults, the following antibiotic regimens may be used: A fluoroquinolone (such as ciprofloxacin 500 mg orally every 12 hours for 3 to 5 days) Azithromycin 500 mg orally on day 1 and 250 mg once a day for 4 days Ceftriaxone 2 g / day IV for 5 days For children, the following antibiotic regimens may be used: Ceftriaxone 50 mg / kg (maximum 1.5 g) IV once a day for 5 days Azithromycin 10 to 12 mg / kg orally as a single dose on day 1, followed by 6 mg / kg (maximum 250 mg) once a day for 4 days Many Shigella isolates are likely to be resistant to ampicillin, trimethoprim / sulfamethoxazole (TMP / SMX), and tetracyclines, but patterns of resistance vary by geographic region.