What is the recommended dose of Augmentin (amoxicillin-clavulanate) for a 72-year-old female patient with a urinary tract infection (UTI), glomerular filtration rate (GFR) of 72, and creatinine level of 0.71?

Augmentin Dosing for UTI in a 72-Year-Old Female with GFR 72

For this patient with a GFR of 72 mL/min, standard adult dosing of Augmentin 875 mg/125 mg twice daily is appropriate without dose adjustment, as renal dose modification is only required when GFR falls below 30 mL/min. 1

Renal Function Assessment

This patient's renal function is mildly reduced but does not require dose adjustment:

• GFR of 72 mL/min represents Stage 2 CKD (mild reduction) and is well above the threshold requiring Augmentin dose modification 2
• The creatinine of 0.71 mg/dL is within normal range for a 72-year-old female, though GFR provides a more accurate assessment of renal function than serum creatinine alone 3
• Creatinine clearance naturally decreases with age even without kidney disease, and elderly women typically have lower values than younger adults 3

Recommended Dosing Regimen

Standard adult dosing applies:

• Augmentin 875 mg/125 mg orally every 12 hours for uncomplicated UTI 1
• Alternative: 500 mg/125 mg every 8 hours if the 875 mg formulation is not tolerated 1
• Duration: Typically 7-10 days for uncomplicated UTI, though specific duration should be based on clinical response 1, 4

Renal Dosing Thresholds (For Reference)

The FDA prescribing information provides clear cutoffs for when dose adjustment becomes necessary 1:

• GFR ≥30 mL/min: No dose adjustment required - use standard adult dosing
• GFR 10-30 mL/min: Reduce to 500 mg/125 mg or 250 mg/125 mg every 12 hours
• GFR <10 mL/min: Reduce to 500 mg/125 mg or 250 mg/125 mg every 24 hours
• Hemodialysis patients: 500 mg/125 mg or 250 mg/125 mg every 24 hours with additional dose during and after dialysis

Critical caveat: The 875 mg/125 mg dose should NOT be used in patients with GFR <30 mL/min 1

Clinical Efficacy Evidence

Augmentin demonstrates strong efficacy for UTI treatment:

• Clinical trials in complicated UTI and pyelonephritis showed 81% bacteriologic success rates at 2-4 days post-therapy with the 875 mg twice daily regimen 1
• The combination of amoxicillin and clavulanic acid achieves approximately 70-85% success rates in treating UTIs caused by resistant organisms 4, 5
• The twice-daily 875 mg/125 mg regimen has comparable efficacy to the three-times-daily 500 mg/125 mg regimen but with significantly less diarrhea (1% vs 2% severe diarrhea) 1

Pharmacokinetic Considerations

While this patient doesn't require adjustment, understanding the pharmacokinetics is important 6:

• Both amoxicillin and clavulanic acid clearance decrease with declining renal function, but amoxicillin clearance decreases more dramatically 6
• At GFR 75 mL/min (similar to this patient), the ratio of amoxicillin to clavulanic acid exposure remains appropriate at approximately 4.9:1 6
• This balanced ratio ensures adequate clavulanic acid levels to inhibit beta-lactamases while preventing amoxicillin accumulation 6

Important Clinical Pitfalls

• Do not rely solely on serum creatinine to assess renal function in elderly patients, as muscle mass decreases with age can mask renal impairment 3
• Do not substitute tablet formulations: Two 250 mg/125 mg tablets do NOT equal one 500 mg/125 mg tablet due to different clavulanic acid content 1
• Monitor for diarrhea: This is the most common adverse effect, occurring in approximately 15% of patients on the twice-daily regimen 1