Nitrofuran (urinary antibacterial)
Nitrofurantoin is an antibiotic used to treat uncomplicated lower urinary tract infections (acute cystitis). It is effective against many common urinary bacteria and is taken orally, usually 3 to 4 times a day.
Also known as: Furadantina, Macrodantina
Antacids containing magnesium trisilicate reduce nitrofurantoin absorption and may decrease antibiotic effectiveness.
The nitrofurantoin SmPC documents decreased absorption with magnesium trisilicate (present in some antacids). Reduced absorption may compromise antibacterial efficacy in a urinary infection. Advise separating doses or avoiding antacids during treatment.
Absorption: magnesium trisilicate decreases nitrofurantoin absorption. Separate the doses (at least 2–3 h) or avoid the combination during treatment.
Chelation/adsorption of the drug by the antacid in the gastrointestinal tract.
Clinical response to antibiotic therapy.
Persisting urinary infection symptoms.
Separate the doses (minimum 2–3 h) or stop the antacid during treatment.
EMC-UK (MHRA) — approved Nitrofurantoin SmPC: https://www.medicines.org.uk/emc/product/100018/smpc ; PubMed — https://pubmed.ncbi.nlm.nih.gov/6995091/ ; Prontuário Terapêutico do INFARMED (11th ed., 2012)
Food increases nitrofurantoin absorption and reduces gastrointestinal discomfort (nausea and vomiting).
Take the capsules with food or milk to improve gastrointestinal tolerability.
EMC-UK (MHRA) — approved Nitrofurantoin SmPC: https://www.medicines.org.uk/emc/product/100018/smpc
Nitrofurantoin is contraindicated with creatinine clearance below 45–60 ml/min (or anuria/oliguria): excretion is impaired, with a risk of toxicity (especially peripheral neuropathy) and inefficacy.
Do not use in patients with creatinine clearance <45 ml/min; in cases with clearance 30–44 ml/min, use only short courses for uncomplicated lower urinary tract infection due to resistant pathogens, when benefit outweighs risk.
EMC-UK (MHRA) — approved Nitrofurantoin SmPC: https://www.medicines.org.uk/emc/product/100018/smpc ; Prontuário Terapêutico do INFARMED (11th ed., 2012)
Glucose-6-phosphate dehydrogenase (G6PD) deficiency predisposes to haemolytic anaemia with nitrofurantoin.
Contraindicated in patients with G6PD deficiency; consider an alternative antibacterial.
EMC-UK (MHRA) — approved Nitrofurantoin SmPC: https://www.medicines.org.uk/emc/product/100018/smpc ; Prontuário Terapêutico do INFARMED (11th ed., 2012)
Acute, subacute and chronic pulmonary reactions (including fibrosis) have been observed with nitrofurantoin, especially in long-term treatment.
Use with caution in patients with pulmonary disease; stop the drug at the first sign of respiratory symptoms or paraesthesias.
DailyMed/FDA (NIH/NLM) — approved Nitrofurantoin label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=55c75f27-b5fc-4f19-8607-08f8ec0c69ec ; EMC-UK (MHRA) — approved Nitrofurantoin SmPC: https://www.medicines.org.uk/emc/product/100018/smpc
Nitrofurantoin has extensive documented use in pregnancy, with no evidence of teratogenicity; it is, however, contraindicated at term (38–42 weeks), during labour and delivery and in infants under 3 months, due to the possibility of haemolytic anaemia from immature erythrocyte enzyme systems.
Usable in the 1st and 2nd trimesters when indicated (uncomplicated lower urinary tract infection); contraindicated from term onwards and during labour.
Excreted in small amounts into breast milk; temporarily avoid breastfeeding if the infant has G6PD deficiency or a suspected erythrocyte enzyme deficiency.
No specific contraception needed.
EMC-UK (MHRA) — approved Nitrofurantoin SmPC: https://www.medicines.org.uk/emc/product/100018/smpc ; Prontuário Terapêutico do INFARMED (11th ed., 2012)
Clinical and educational support tool. The information does not replace a medical prescription or the opinion of a qualified healthcare professional.
Antibacterial agent indicated for the treatment and prevention of urinary tract infections. It concentrates in urine (to which it often imparts a brown colour), where it exerts its action; plasma concentrations after an oral dose are low, with peaks usually below 1 mcg/ml.
Intracellular reduction of nitrofurantoin generates reactive intermediates that inhibit bacterial enzymes and damage DNA, RNA and other macromolecules of susceptible bacteria.
The capsule contains two forms: 25% macrocrystalline (slower dissolution and absorption) and 75% monohydrate, which forms a gel matrix releasing the drug over time. When administered with food, bioavailability increases by about 40%.
Nitrofurantoin is rapidly absorbed and a large proportion is metabolised in the tissues; about 20 to 25% of a single dose is recovered unchanged in urine within 24 hours.
The plasma half-life is short (of the order of 20 to 60 minutes), reflecting rapid metabolism and elimination; the drug is highly soluble in urine.
Medicines from the same therapeutic group (ATC classification) or the same pharmacological class.
