From the Research
Macrobid (nitrofurantoin) can be used with caution in an elderly patient with an eGFR of 56 for a 7-day course. The most recent and highest quality study, published in 2018 1, suggests that nitrofurantoin can be used in patients with an eGFR <60 mL/minute/1.73 m2 without an increased risk of adverse outcomes. In fact, this study found that nitrofurantoin was associated with lower odds of hospitalization for acute kidney injury compared to trimethoprim.
Key Considerations
- The standard dosing for Macrobid (nitrofurantoin) is 100 mg twice daily for 7 days.
- Close monitoring for adverse effects, particularly pulmonary symptoms (cough, shortness of breath), is essential, as elderly patients are at higher risk for nitrofurantoin toxicity.
- Reduced renal function may lead to lower urinary concentrations (reducing efficacy) and higher serum levels (increasing toxicity risk).
- Alternative antibiotics like trimethoprim-sulfamethoxazole or cephalexin might be considered if the patient has significant renal impairment or is at high risk for adverse effects.
- Ensuring adequate hydration during treatment is crucial to help maintain urine flow and drug concentration.
Rationale
The use of estimated glomerular filtration rate (eGFR) for dose adjustment of medications in the elderly is important to avoid overdosing 2. However, in the case of nitrofurantoin, the most recent evidence suggests that it can be used with caution in patients with an eGFR between 30-60 ml/min for short-term treatment of uncomplicated urinary tract infections 1. This is consistent with the findings of other studies, which have shown that the presence of mild or moderate reductions in eGFR does not justify avoidance of nitrofurantoin 3.
Monitoring and Precautions
It is essential to closely monitor the patient for adverse effects, particularly pulmonary symptoms, and to ensure adequate hydration during treatment. The patient's renal function should also be closely monitored, and the dose of nitrofurantoin adjusted accordingly. Alternative antibiotics should be considered if the patient has significant renal impairment or is at high risk for adverse effects.