Nitrofurantoin should be avoided in individuals with CrCl below what threshold?

• A. 30 mL/min
• B. 60 mL/min
• C. 15 mL/min
• D. 45 mL/min

Answer: (A)

Nitrofurantoin works best as a urinary tract antiseptic because it concentrates in the urine, and its effectiveness depends on adequate renal clearance. When creatinine clearance falls below about 30 mL/min, the drug may not reach sufficient urinary concentrations to treat a UTI effectively, and there is a greater risk of drug accumulation with potential toxicity (such as pulmonary, hepatic, or neuropathic effects) with longer exposure. Because of these concerns, Beers Criteria recommends avoiding nitrofurantoin when CrCl is under 30 mL/min.