Macrobid (Nitrofurantoin) Dosing and Treatment for Urinary Tract Infections
For acute uncomplicated lower urinary tract infections (cystitis), prescribe nitrofurantoin 100 mg twice daily for 5 days. 1
Treatment Regimen for Acute Uncomplicated Cystitis
- Standard dosing is nitrofurantoin 100 mg orally twice daily for 5 days, which achieves clinical and microbiological cure rates of 90-92% 1
- This regimen is recommended by the Infectious Diseases Society of America and European Society of Clinical Microbiology and Infectious Diseases as highly effective first-line therapy 1
- The World Health Organization classifies nitrofurantoin as an Access (A) category antibiotic for lower urinary tract infections, making it a preferred first-line agent 2
Evidence on Treatment Duration
While 5-day courses are the current standard, the evidence base shows some variation:
- Avoid single-dose therapy: Single-dose antibiotics show significantly higher rates of bacteriological persistence compared to 3-6 day courses (RR 2.01) or 7-14 day courses (RR 1.93) 2
- 3-day courses may be effective in select populations: Studies in children demonstrated equivalent efficacy between 3-day and 10-day courses for presumed lower UTI (relapse rates 7.7% vs 8.7%, not statistically different) 3
- However, 5-day courses are recommended over 3-day courses based on current guideline consensus, as direct comparative evidence supporting 3-day nitrofurantoin courses in adults is limited 1, 4
Critical Contraindications and Limitations
Do not use nitrofurantoin for pyelonephritis or systemic infections - it does not achieve adequate serum concentrations for upper tract or systemic disease 1
Contraindicated in the last trimester of pregnancy due to risk of hemolytic anemia in the newborn 1
For pyelonephritis (upper UTI), use ciprofloxacin for mild-to-moderate cases or ceftriaxone/cefotaxime for severe cases instead 2
Prophylactic Dosing for Recurrent UTI
For women with recurrent UTIs, daily prophylactic dosing of nitrofurantoin can be prescribed after discussing risks and benefits 2:
- Daily dosing is the most tested prophylactic schedule 2
- Duration typically ranges from 6-12 months with periodic assessment 2
- Post-coital prophylaxis (single dose after intercourse) is effective for women with UTIs temporally related to sexual activity 2
Safety Profile
Serious adverse events are extremely rare but must be discussed:
- Pulmonary toxicity risk: 0.001% 2
- Hepatic toxicity risk: 0.0003% 2
- Common minor effects include gastrointestinal disturbances and skin rash 2
Advantages in Resistant Infections
Nitrofurantoin maintains effectiveness against multidrug-resistant pathogens: