What is the appropriate amoxicillin‑clavulanate dose for a urinary tract infection in a 6‑year‑old male weighing 46 lb?

Amoxicillin-Clavulanate Dosing for UTI in a 6-Year-Old Male Weighing 46 Pounds

For a 6-year-old male weighing 46 pounds (21 kg) with a urinary tract infection, administer amoxicillin-clavulanate at 20–40 mg/kg/day of the amoxicillin component divided into 3 doses for 7–10 days, which translates to approximately 140–280 mg three times daily (or 3.5–7 mL of 200 mg/5 mL suspension three times daily). 1

Weight-Based Calculation

• The child weighs 46 pounds, which converts to approximately 21 kg (46 ÷ 2.2 = 20.9 kg).
• Using the guideline-recommended dosing range of 20–40 mg/kg/day divided into 3 doses, the total daily dose ranges from 420 mg to 840 mg per day. 1
• This translates to 140–280 mg per dose administered three times daily.

Recommended Dosing Regimen

• Start with the standard dose of 20 mg/kg/day (420 mg/day total, or 140 mg three times daily) for uncomplicated UTI in a child without recent antibiotic exposure or risk factors for resistant organisms. 1
• Consider the higher end of the range (40 mg/kg/day, or 280 mg three times daily) if the child has received antibiotics within the past 30 days, attends daycare, or if local resistance patterns warrant more aggressive dosing. 1, 2
• Using a 200 mg/5 mL suspension formulation, administer 3.5 mL three times daily for standard dosing or 7 mL three times daily for high-dose therapy. 1

Treatment Duration

• Complete a full 7–10 day course of therapy for pediatric UTI, with most guidelines recommending closer to 10 days for febrile UTIs to reduce the risk of renal scarring. 1
• The minimum duration should be 7 days, as shorter 1–3 day courses have proven inferior for febrile UTIs in children. 1

Clinical Monitoring

• Clinical improvement should be evident within 48–72 hours of initiating appropriate antibiotic therapy; lack of improvement warrants reevaluation and consideration of alternative diagnoses or resistant organisms. 2
• Fever typically resolves within 24–48 hours for most bacterial UTIs, though some symptoms may persist longer. 2

Important Considerations

• Amoxicillin-clavulanate is specifically indicated for UTIs because it achieves therapeutic concentrations in both the bloodstream and urine, making it appropriate for treating potential pyelonephritis or urosepsis—unlike nitrofurantoin, which should be avoided in febrile UTIs. 1
• The addition of clavulanate is essential for coverage of β-lactamase-producing organisms such as E. coli, which account for the majority of pediatric UTIs and frequently demonstrate resistance to amoxicillin alone. 3, 4, 5
• Know local antibiotic susceptibility patterns before prescribing, as geographic variability in resistance significantly impacts empiric antibiotic selection. 1

Route of Administration

• Most children can be treated orally unless they appear toxic, are unable to retain oral intake, or compliance is uncertain—in which case parenteral therapy should be initiated. 1
• For this 6-year-old who is presumably able to take oral medications, oral amoxicillin-clavulanate is the appropriate first-line choice. 1

Common Pitfalls to Avoid

• Do not use agents that only achieve urinary concentrations (such as nitrofurantoin) for febrile UTIs, as inadequate serum levels may fail to treat upper tract disease. 1
• Avoid underdosing—the 20–40 mg/kg/day range is specifically for UTIs and differs from higher respiratory infection dosing (45–90 mg/kg/day). 1, 2
• Do not stop antibiotics early even if symptoms improve; completing the full 7–10 day course is essential to prevent relapse and reduce the risk of renal scarring. 1, 3, 4