Nitrofurantoin relies on renal excretion into the bladder. Screen for renal function, G6PD deficiency, and pulmonary history before prescribing.
Absolute contraindications include hypersensitivity to nitrofurantoin and significant renal impairment (CrCl <30 mL/min/1.73 m²). Relative precautions involve G6PD deficiency, late-term pregnancy, premature infants, and chronic pulmonary disease.
Hypersensitivity to nitrofurantoin or formulation excipients — prior pulmonary reactions, cholestatic hepatitis, or severe cutaneous responses mandate permanent avoidance and prompt allergy documentation.
Anuria or significant renal impairment (creatinine clearance <30 mL/min/1.73 m²), because therapeutic urinary concentrations will not be achieved and systemic accumulation heightens neurotoxicity and pulmonary risk.
Glucose-6-phosphate dehydrogenase deficiency; oxidative hemolysis has been reported in infants and children, so use only with specialist oversight and arrange close hemoglobin monitoring.
Late third-trimester pregnancy (38–42 weeks) or peripartum use, due to the potential for neonatal hemolytic anemia; select an alternative agent if delivery is imminent.
Breastfeeding premature infants or those with G6PD deficiency, because trace drug in milk can precipitate hemolysis — consider postponing lactation or choosing an alternate antibiotic.
Chronic pulmonary disease or history of nitrofurantoin-induced lung injury; assess baseline oxygen saturation and counsel families to stop therapy immediately if cough or dyspnea develops.