What Augmentin (amoxicillin‑clavulanate) dose and duration should be used in an adult with an uncomplicated urinary‑tract infection, and how should it be adjusted for complicated infection or moderate renal impairment?

Augmentin Dosing for Urinary Tract Infections

For uncomplicated UTI in adults, Augmentin is not a first-line agent and should only be used when preferred antibiotics (nitrofurantoin, fosfomycin, or trimethoprim-sulfamethoxazole) cannot be used; if prescribed, use 500 mg/125 mg every 12 hours for 3–7 days. 1, 2

Uncomplicated Cystitis in Women

First-Line Agents (Not Augmentin)

• Nitrofurantoin 100 mg twice daily for 5 days is preferred 1
• Fosfomycin 3 g single dose is preferred 1
• Trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days if local resistance <20% 1

When to Consider Augmentin

Augmentin should only be prescribed when first-line agents are contraindicated due to allergy, intolerance, or documented resistance. 1

• Beta-lactams including Augmentin have inferior efficacy and more adverse effects compared with other UTI antimicrobials and should be used with caution. 1
• Clinical trial data show Augmentin achieves only 58% clinical cure versus 77% with ciprofloxacin, even when the organism is susceptible to Augmentin 3
• This inferior performance is due to Augmentin's poor ability to eradicate vaginal E. coli colonization (45% vaginal colonization with Augmentin vs 10% with ciprofloxacin), facilitating early reinfection 3

Dosing for Uncomplicated Cystitis

If Augmentin must be used: 500 mg/125 mg every 12 hours for 3–7 days 1, 2

• The FDA label specifies 500 mg/125 mg every 12 hours as the standard adult dose 2
• Guidelines recommend 3–7 day regimens for beta-lactams in uncomplicated cystitis 1
• Do NOT substitute two 250 mg/125 mg tablets for one 500 mg/125 mg tablet — they contain the same amount of clavulanic acid (125 mg) and are not equivalent 2

Complicated UTI and Pyelonephritis

Complicated UTI Dosing

For complicated UTI: 875 mg/125 mg every 12 hours for 7–14 days 2

• The FDA label recommends 875 mg/125 mg every 12 hours for "more severe infections" 2
• Clinical trial data in complicated UTI showed comparable efficacy between 875 mg/125 mg every 12 hours versus 500 mg/125 mg every 8 hours 2
• Bacteriologic cure rates at 2–4 weeks post-therapy were 52% (875 mg/125 mg q12h) and 55% (500 mg/125 mg q8h) 2

Pyelonephritis Considerations

Oral beta-lactams including Augmentin are NOT recommended for pyelonephritis unless preceded by a parenteral dose of ceftriaxone 1 g IV or an aminoglycoside. 1

• Fluoroquinolones (ciprofloxacin 500 mg twice daily for 7 days or levofloxacin 750 mg daily for 5 days) are preferred for pyelonephritis if local resistance <10% 1
• If fluoroquinolone resistance exceeds 10%, give ceftriaxone 1 g IV once, then consider oral therapy 1
• Oral beta-lactams have insufficient tissue penetration for upper tract infections when used alone 1

Renal Impairment Dosing

For moderate renal impairment (CrCl 10–30 mL/min): 500 mg/125 mg every 24 hours or 250 mg/125 mg every 12 hours 2

• The FDA label provides specific guidance: patients with creatinine clearance 10–30 mL/min should receive reduced frequency dosing 2
• For severe renal impairment (CrCl <10 mL/min): 500 mg/125 mg every 24 hours or 250 mg/125 mg every 24 hours 2
• Do not use the 875 mg/125 mg formulation in patients with CrCl <30 mL/min 2

Key Clinical Pitfalls

Resistance Concerns

• Amoxicillin alone should NEVER be used empirically for UTI due to very high resistance rates worldwide (>20%) 1
• Even with clavulanate added, Augmentin resistance occurs in 10–15% of E. coli isolates 3, 4
• Historical data show only 70% success rates for amoxicillin-resistant organisms treated with Augmentin 5

Adverse Effects

• Diarrhea occurs in 14–15% of patients 2
• Severe diarrhea or treatment withdrawal due to diarrhea occurs in 1–2% 2
• Take Augmentin at the start of meals to minimize gastrointestinal intolerance and enhance clavulanate absorption 2

Treatment Failures

• If symptoms persist or recur within 2 weeks, obtain urine culture and assume resistance to Augmentin; use a different antimicrobial for 7 days 6
• Bacteriologic cure rates are significantly lower with 3-day versus 5–10 day regimens (RR 1.43 for failure with 3-day therapy) 7
• For women requiring bacteriologic eradication (recurrent UTI, immunosuppression), use 7-day regimens rather than 3-day courses 7

Men with UTI

For men with uncomplicated UTI: trimethoprim-sulfamethoxazole 160/800 mg twice daily for 7 days is preferred over Augmentin 6

• Men require longer treatment duration (7 days minimum) compared to women (3–7 days) 6
• If Augmentin must be used in men: 500 mg/125 mg every 12 hours for 7 days 1, 2