What is the recommended amoxicillin/clavulanate (Augmentin) dosage for an uncomplicated urinary tract infection in a 33‑kg child?

Augmentin Dosing for UTI in a 33-kg Child

For an uncomplicated urinary tract infection in a 33-kg child, prescribe amoxicillin-clavulanate (Augmentin) at 20–40 mg/kg/day of the amoxicillin component, divided into three doses every 8 hours, which translates to approximately 660–1320 mg/day total (220–440 mg per dose), given three times daily for 7–14 days. 1, 2

Weight-Based Calculation for This Patient

• Standard dosing: 20–40 mg/kg/day of amoxicillin component divided into 3 doses 2
• For 33 kg:
  • Low end: 20 mg/kg/day = 660 mg/day ÷ 3 = 220 mg per dose
  • High end: 40 mg/kg/day = 1320 mg/day ÷ 3 = 440 mg per dose
• Practical prescription: Use 250–500 mg of amoxicillin component three times daily (every 8 hours) 1, 2

Critical Dosing Restrictions

• Do NOT use high-dose regimens (90 mg/kg/day) for uncomplicated UTI—this dosing is reserved exclusively for respiratory infections like pneumonia and otitis media, not urinary tract infections 3, 2
• Maximum daily dose: Never exceed 4000 mg/day of amoxicillin regardless of weight 3, 1, 2
• For this 33-kg child, even the high end of standard UTI dosing (1320 mg/day) remains well below the 4000 mg maximum 1

Treatment Duration

• 7–14 days is the recommended course for pediatric UTI 1
• Shorter courses (1–3 days) are inferior for febrile UTIs and should be avoided 1

Formulation Selection

For a 33-kg child (typically 8–12 years old):

• Oral suspension: 250 mg/62.5 mg per 5 mL, give 5 mL three times daily 2
• Tablets: 250 mg/125 mg tablets, give 1–2 tablets three times daily depending on severity 2

Expected Clinical Response

• Clinical improvement (reduced fever, decreased dysuria) should occur within 48–72 hours 2
• If no improvement or worsening after 48–72 hours, obtain repeat urine culture and reassess antibiotic choice based on susceptibility results 2

Common Pitfalls to Avoid

• Verify suspension concentration before dispensing—125/31 mg per 5 mL versus 250/62 mg per 5 mL formulations exist, and dosing errors are common 2
• Do not confuse UTI dosing with pneumonia dosing—the 90 mg/kg/day regimen used for respiratory infections increases diarrhea risk (≈25% incidence) without benefit for UTI 2
• Adjust for renal impairment: If this child has known renal dysfunction (eGFR <30 mL/min/1.73 m²), reduce dose and extend interval to every 12 hours instead of every 8 hours 2

Alternative Agents if Co-amoxiclav Fails

If culture shows resistance or clinical failure occurs:

• Cefixime 8 mg/kg/day as single daily dose 1
• Cefpodoxime 10 mg/kg/day divided into 2 doses 1
• Trimethoprim-sulfamethoxazole (84.9% susceptibility) or nitrofurantoin (93.3% susceptibility) based on local resistance patterns 1