What is the recommended dose of Macrobid (nitrofurantoin monohydrate) for an adult woman with uncomplicated acute cystitis?

Macrobid Dosing for Acute Cystitis

For uncomplicated acute cystitis in adult women, prescribe Macrobid (nitrofurantoin monohydrate/macrocrystals) 100 mg orally twice daily for 5 days. 1, 2

Standard Dosing Regimen

• The 5-day course is the optimal duration, achieving clinical cure rates of 84-90% and bacterial cure rates of 92% at early follow-up (5-9 days post-treatment). 1
• At 30-day follow-up, clinical cure rates remain robust at 84%, demonstrating sustained efficacy. 1
• This regimen has comparable efficacy to trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days when local resistance is low. 3, 2

Alternative Duration Option

• A 7-day course (100 mg twice daily) is acceptable if you prefer a longer duration, with clinical cure rates of 89-93% and bacterial cure rates of 86%. 1
• The 7-day regimen shows equivalent efficacy to ciprofloxacin and trimethoprim-sulfamethoxazole when comparing similar duration courses. 1
• Avoid 3-day regimens (100 mg four times daily) due to inferior efficacy, with only 88% clinical cure and 74% bacterial cure rates. 1

Critical Contraindications

• Do not use nitrofurantoin if creatinine clearance is <60 mL/min, as inadequate urinary drug concentrations prevent bactericidal activity and increase toxicity risk. 1
• Do not use if early pyelonephritis is suspected, as nitrofurantoin does not achieve adequate tissue concentrations for upper tract infections. 1, 2

Common Pitfalls to Avoid

• Prescribing excessive duration: Most prescriptions in primary care are longer than guideline recommendations (73% of nitrofurantoin prescriptions exceed recommended duration), which increases adverse effects without additional benefit. 4
• Using fluoroquinolones as first-line: Despite their high efficacy, fluoroquinolones should be reserved for more invasive infections due to collateral damage and resistance concerns. 3, 5

Expected Adverse Effects

• Nausea and headache are the most common side effects, occurring in 5.6-34% of patients depending on the study. 1, 2
• Advise adequate hydration during treatment to prevent crystal formation. 2

When to Choose Alternative First-Line Agents

• If CrCl <60 mL/min: Switch to trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days (only if local E. coli resistance <20%) or fosfomycin 3 g single dose. 1
• If patient has sulfa allergy and normal renal function: Fosfomycin 3 g single dose is an alternative, though it has slightly lower efficacy (90% vs 95% clinical cure for nitrofurantoin). 1
• If local trimethoprim-sulfamethoxazole resistance is <20% and patient has no contraindications: Trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days is an equivalent alternative. 3, 1