What is the recommended dose of Macrobid (nitrofurantoin) for a 17-year-old patient with a urinary tract infection?

Macrobid Dosing for a 17-Year-Old

For a 17-year-old with uncomplicated UTI, prescribe Macrobid (nitrofurantoin monohydrate/macrocrystals) 100 mg twice daily for 5-7 days. 1

Dosing Rationale

A 17-year-old falls into the pediatric dosing category of ≥12 years, where the recommended dose is 100 mg twice daily 1. This aligns with the standard adult dosing regimen endorsed by the Infectious Diseases Society of America and European guidelines for uncomplicated urinary tract infections 1.

Treatment Duration

• 5 days is the optimal duration for uncomplicated cystitis, balancing efficacy with minimizing antibiotic exposure and adverse effects 1
• Extend to 7 days if there are any complicating factors or if symptoms persist 1
• The pediatric literature specifically recommends at least 3 days after obtaining sterile urine, with a typical 7-day course for children 1

Gender-Specific Considerations

If this patient is male, important modifications apply:

• Treatment duration should be 7-14 days (not 5 days), with 14 days recommended when prostatitis cannot be excluded 2
• Nitrofurantoin has substantially lower efficacy in males, with a 25% failure rate versus 10-16% in females 2
• Consider alternative agents like trimethoprim-sulfamethoxazole or fluoroquinolones for males with UTI 2

Critical Contraindications to Screen For

Before prescribing, ensure the patient does NOT have:

• Suspected pyelonephritis (fever, flank pain, systemic symptoms) - nitrofurantoin does not achieve adequate renal tissue concentrations 1
• Creatinine clearance <30 mL/min (or <60 mL/min per some guidelines) - increased risk of peripheral neuropathy and inadequate urinary drug concentrations 1, 2
• Complicated UTI features (structural abnormalities, obstruction, immunosuppression) 1

Expected Outcomes and Monitoring

• Clinical cure rates: 88-93% for uncomplicated UTIs 1
• Bacterial cure rates: 81-92% 1
• Patients should experience symptom improvement within 48-72 hours 2
• If symptoms persist or recur within 2 weeks, obtain urine culture with susceptibility testing and consider retreatment with a 7-day regimen using another agent 1

Common Side Effects to Counsel About

• Nausea and headache are most common, occurring in 5.6-34% of patients 1
• Advise adequate hydration during treatment to prevent crystal formation 1
• Serious pulmonary and hepatic toxicity are extremely rare (0.001% and 0.0003% respectively) 1