What is the first-line treatment for a patient with cystitis and a penicillin allergy?

First-Line Treatment for Cystitis with Penicillin Allergy

Nitrofurantoin monohydrate/macrocrystals 100 mg twice daily for 5 days is the recommended first-line treatment for uncomplicated cystitis in patients with penicillin allergy. 1, 2

Primary Recommendation

• Nitrofurantoin 100 mg twice daily for 5 days is the optimal choice, as it avoids beta-lactam agents entirely and maintains excellent efficacy against common uropathogens 1, 2
• This regimen achieves clinical cure rates of 84% and is equivalent to other first-line therapies 3
• Nitrofurantoin has minimal collateral damage to normal flora and maintains low resistance rates despite decades of use 1, 2

Alternative First-Line Options (When Nitrofurantoin Cannot Be Used)

If nitrofurantoin is contraindicated (renal impairment with CrCl <60 mL/min, suspected pyelonephritis, or last trimester of pregnancy), consider:

• Trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days - only if local E. coli resistance is <20% and the patient has not used it for UTI in the previous 3 months 1, 2
• Fosfomycin trometamol 3 g single dose - convenient single-dose therapy, though slightly lower efficacy (75-85% cure rate) compared to nitrofurantoin 1, 4

Important Clinical Caveats

• Avoid fluoroquinolones (ciprofloxacin, levofloxacin) as first-line therapy; reserve these for complicated infections or pyelonephritis due to collateral damage, resistance concerns, and FDA warnings about serious adverse effects 1, 2
• Do not use amoxicillin or ampicillin for empirical treatment due to very high resistance rates worldwide 1
• Beta-lactam alternatives (cefadroxil 500 mg twice daily for 3 days, cefpodoxime-proxetil) can be used when other agents cannot, but have inferior efficacy and more adverse effects compared to nitrofurantoin 1

Key Contraindications to Nitrofurantoin

• Suspected pyelonephritis (fever, flank pain, systemic symptoms) - nitrofurantoin does not achieve adequate tissue concentrations 1, 2
• Creatinine clearance <60 mL/min 2
• Infants under 4 months of age 2
• Last trimester of pregnancy 1

When to Obtain Urine Culture

• Urine culture is not necessary before starting empiric therapy for typical uncomplicated cystitis 2
• Do obtain culture if: symptoms suggesting pyelonephritis, atypical presentation, pregnancy, symptoms not resolving or recurring within 4 weeks, or in men 1, 4