Primary pathogens (Escherichia coli · Klebsiella species · Proteus mirabilis · Enterococcus species (less common))
Clinical context (Upper urinary tract infection · fever · flank or abdominal pain · systemic symptoms · may occur with normal or abnormal renal anatomy)
First-line therapy
Ceftriaxone • i.v. • 50–75 mg/kg/day • 1×/day
Max 2000 mg/day · Duration: 7–10 days · Total IV plus oral course; extend to 10–14 days if slow response or complicated UTI
Dose is calculated using the amoxicillin component.
Max 875 mg/dose (amoxicillin) · Duration: 7–10 days · Step-down or oral therapy when clinically stable; total IV plus oral duration 7–10 days (up to 14 if complicated)
• Amoxicillin/clavulanate: step-down when culture confirms susceptibility; covers beta-lactamase–producing E. coli per local antibiogram.
• Cefixime: preferred oral step-down in many regions (CPS); use when isolate susceptible and patient tolerates oral therapy.
• Initial p.o. therapy without IV may be appropriate in nontoxic children >2–3 months with reliable follow-up per AAP/CPS — hospitalize if ill-appearing or unable to tolerate oral intake.
• Cefalexin 25 mg/kg/dose p.o. 3×/day for 7 days is an alternative oral step-down when susceptibility is confirmed (not listed as primary tier here).
Enter weight on Kids to calculate doses
Clinical notes
• Obtain urine culture by catheter or suprapubic aspirate before antibiotics when feasible; bag specimens are for screening only — confirm with invasive collection when culture will guide therapy.
• Hospital admission: toxic appearance, dehydration, vomiting precluding oral intake, age <2–3 months (per local protocol), failed outpatient therapy, or suspected complicated UTI (obstruction, abscess).
• Switch i.v. → p.o. when afebrile 24–48 h, clinically improved, tolerating oral fluids, and oral agent matches susceptibilities (typically after 48–72 h of IV therapy).
• Follow-up: recheck clinically in 48–72 h; repeat urine culture after treatment per local protocol if recurrent UTI or abnormal anatomy; renal/bladder ultrasound for febrile UTI in infants per AAP/CPS/ESPU.
• Total antibiotic duration 7–10 days (IV plus oral combined); extend to 10–14 days for infants, slow response, or complicated infection.
• AAP — Urinary Tract Infection Clinical Practice Guideline (2011)
• AAP Red Book — Urinary Tract Infections (2024)
• Canadian Paediatric Society — Urinary tract infections in children (2024)
