What is the recommended oral dose of amoxicillin for an elderly patient with severe chronic kidney disease (creatinine clearance of 25) and a presumed urinary tract infection (UTI)?

Amoxicillin Dosing for CrCl 25 mL/min

For an elderly patient with severe chronic kidney disease (CrCl 25 mL/min) and a presumed UTI, amoxicillin should be dosed at 500 mg or 250 mg every 12 hours, depending on infection severity. 1

Specific Dosing Recommendations

For patients with creatinine clearance between 10-30 mL/min:

• 500 mg every 12 hours for moderate to severe infections 1
• 250 mg every 12 hours for mild infections 1
• The 875 mg dose formulation should NOT be used in patients with GFR <30 mL/min 1

Key Clinical Considerations

Timing and duration:

• Continue treatment for a minimum of 48-72 hours beyond symptom resolution or evidence of bacterial eradication 1
• For streptococcal infections, maintain treatment for at least 10 days to prevent acute rheumatic fever 1

Important safety points:

• Amoxicillin remains a viable option for UTI treatment in severe CKD, as penicillins and derivatives can reach active urinary concentrations even with low GFR 2
• The absorption half-life of amoxicillin increases significantly in renal impairment, which supports the extended dosing intervals 3
• Monitor closely for hypersensitivity reactions, as serious anaphylactic reactions can occur with penicillin therapy 1

Common Pitfalls to Avoid

Do not use standard dosing:

• Avoid the 875 mg every 12 hours regimen commonly used in patients with normal renal function 1
• The Cockroft-Gault equation is the most accurate for estimating amoxicillin clearance in hospitalized patients, superior to MDRD or CKD-EPI 4

Resistance considerations:

• Be aware that beta-lactam resistance is increasingly common in CKD patients with UTIs, with studies showing up to 94.67% ampicillin resistance in urinary isolates 5
• If clinical response is inadequate after 48-72 hours, consider alternative antibiotics based on culture and sensitivity results 5