What oral antibiotic regimen is appropriate for a 70‑year‑old woman with acute uncomplicated cystitis (dysuria, hematuria, leukocyturia, no costovertebral angle tenderness) who is allergic to cefaclor, doxycycline, levofloxacin, trimethoprim‑sulfamethoxazole, ciprofloxacin, sulfonamides, and amoxicillin‑clavulanate?

Treatment Recommendation for Acute Uncomplicated Cystitis with Multiple Antibiotic Allergies

Given this patient's extensive allergy profile excluding most first-line agents, nitrofurantoin monohydrate/macrocrystals 100 mg twice daily for 5 days is the recommended treatment, provided her eGFR is >30 mL/min. 1, 2, 3

Primary Treatment Option

• Nitrofurantoin 100 mg twice daily for 5 days is the optimal choice for this patient, as it remains highly effective against E. coli (the most common uropathogen), has minimal resistance patterns, and is not contraindicated by any of her reported allergies 4, 1, 3
• This regimen achieves clinical cure rates of 90-93% and is recommended as first-line therapy by the Infectious Diseases Society of America 4, 3
• Critical caveat: Nitrofurantoin must be avoided if her eGFR is <30 mL/min due to reduced efficacy and increased risk of toxicity 1

Alternative if Nitrofurantoin is Contraindicated

• Fosfomycin trometamol 3 g as a single oral dose is the appropriate alternative if renal function is impaired (eGFR <30 mL/min) or if nitrofurantoin cannot be used for other reasons 1, 2, 5
• Fosfomycin provides adequate urinary concentrations without requiring dose adjustment for renal impairment, with clinical cure rates of 90-91% 1
• The single-dose regimen should be mixed with water before ingesting, and may be taken with or without food 5
• While slightly less effective than multi-day regimens, fosfomycin remains an appropriate first-line option when other agents cannot be used 4, 2

Why Other Options Are Excluded

• Trimethoprim-sulfamethoxazole, Bactrim, and sulfa drugs: All contraindicated by her sulfa allergy 4, 3
• Ciprofloxacin and levofloxacin: Both contraindicated by her documented fluoroquinolone allergies 4, 3
• Augmentin (amoxicillin-clavulanate): Contraindicated by her documented allergy 4, 3
• Doxycycline: Contraindicated by her documented allergy and not a recommended agent for cystitis 4
• Cefaclor: Contraindicated by her documented allergy, though other oral cephalosporins could theoretically be considered 4

Consideration of Other Cephalosporins (Use with Extreme Caution)

• Oral cephalosporins such as cefdinir, cefpodoxime-proxetil, or cephalexin for 3-7 days could be considered only if both nitrofurantoin and fosfomycin are contraindicated 4, 3
• Major concern: Her allergy to cefaclor (a 2nd generation cephalosporin) raises the possibility of cross-reactivity with other cephalosporins 1
• Patients with documented cephalosporin allergy should avoid other cephalosporins without formal allergy testing due to cross-reactivity concerns 1
• These agents have inferior efficacy (lower cure rates) and more adverse effects compared to nitrofurantoin or fosfomycin 4, 3
• This option should only be pursued after consultation with allergy/immunology or infectious disease specialists 1

Essential Clinical Actions

• Verify renal function immediately before prescribing nitrofurantoin, as eGFR <30 mL/min is an absolute contraindication 1
• Obtain urine culture with susceptibility testing given her complex allergy profile and the need to confirm appropriate antibiotic selection 1
• Reassess in 2-3 days if symptoms do not improve, as this may indicate resistance or an incorrect diagnosis 4, 3
• Consider formal allergy testing for her multiple reported antibiotic allergies, as many reported "allergies" are actually intolerances or non-IgE-mediated reactions that do not preclude future use 1

Common Pitfalls to Avoid

• Do not use amoxicillin or ampicillin even if she tolerates them, as they have very high resistance rates worldwide and poor efficacy for empirical treatment 4, 3
• Do not prescribe nitrofurantoin for longer than 7 days or in patients with eGFR <30 mL/min, as this increases toxicity risk without improving efficacy 1
• Do not assume all reported allergies are true IgE-mediated hypersensitivity reactions—many patients report side effects or intolerances as "allergies," which unnecessarily limits treatment options 1