1. Clinical & Scientific Overview
Nitrofurantoin (Macrocrystals & Sustained-Release Monohydrate/Macrocrystals) (TIP-MED-000140, Reference Code [8.12]) is classified under
Antimicrobials — Antibacterial & Antibiotic Agents (Ch 08) as a Urinary-Tract-Specific Nitrofuran Bactericidal Antimicrobial (Activated by Bacterial Nitroreductases to Damage Ribosomes & DNA; WHO 'Access' First-Line UTI Agent).
Within the Indian regulatory and compendial framework, it is governed under Schedule H Prescription Drug (To be sold by retail on the prescription of a Registered Medical Practitioner only — Drugs Rules 1945).
Representative Indian Market Examples (Edition 2.7 Ch 08 [8.12], p. 98): Furadantin (GSK—50 mg, 100 mg IR), Martifur-MR / Nifty-SR / Uribid / Niftas (Intas—100 mg SR/MR twice daily) — Strengths & Dosage Forms: Immediate-Release Tablets/Capsules: 50 mg, 100 mg; Sustained/Modified-Release (SR/MR) Tablets: 100 mg SR; Paediatric Suspension: 25 mg/5 mL
Immediate-Release Tablets/Capsules: 50 mg, 100 mg; Sustained/Modified-Release (SR/MR) Tablets: 100 mg SR; Paediatric Suspension: 25 mg/5 mL
3. Mechanism of Action & Pharmacodynamics
Urinary-Tract-Specific Nitrofuran Bactericidal Antimicrobial (Activated by Bacterial Nitroreductases to Damage Ribosomes & DNA; WHO 'Access' First-Line UTI Agent) acting on target receptor/enzyme pathways in Antimicrobials — Antibacterial & Antibiotic Agents (Ch 08): clinical efficacy is mediated via Urinary-Tract-Specific Nitrofuran Bactericidal Antimicrobial (Activated by Bacterial Nitroreductases to Damage Ribosomes & DNA; WHO 'Access' First-Line UTI Agent) for ICMR First-Line Drug of Choice for Uncomplicated Lower Urinary Tract Infections (Acute Cystitis) in women and men, and low-dose long-term prophylaxis of recurrent lower UTIs. (CRITICAL ANATOMICAL LIMITATION: Nitrofurantoin achieves bactericidal concentrations ONLY in the urine/bladder lumen and has ZERO therapeutic tissue concentration in the renal parenchyma or prostate—therefore it is STRICTLY INEFFECTIVE and CONTRAINDICATED for Acute Pyelonephritis [upper UTI with flank pain/high fever], Urosepsis, or Acute Prostatitis!)..
4. Therapeutic Indications & Evidence-Supported Uses
- ICMR First-Line Drug of Choice for Uncomplicated Lower Urinary Tract Infections (Acute Cystitis) in women and men, and low-dose long-term prophylaxis of recurrent lower UTIs
- (CRITICAL ANATOMICAL LIMITATION: Nitrofurantoin achieves bactericidal concentrations ONLY in the urine/bladder lumen and has ZERO therapeutic tissue concentration in the renal parenchyma or prostate—therefore it is STRICTLY INEFFECTIVE and CONTRAINDICATED for Acute Pyelonephritis [upper UTI with flank pain/high fever], Urosepsis, or Acute Prostatitis!)
🇮🇳 Jurisdiction & Indication Note: Indications and schedules reflect Indian compendial and regulatory records (CDSCO / Indian Pharmacopoeia & NFI / NLEM 2022). Where international reference labels (US FDA DailyMed / NCBI StatPearls) are cited for pharmacokinetic or mechanistic parameters, international approvals do not automatically imply CDSCO approval in India.
5. Educational Dosage Context, Formulations & Administration
Educational Dosing & Regimen Summary: General Adult Reference: Acute Uncomplicated Cystitis: 100 mg SR/MR twice daily (every 12 hours) (or 50–100 mg IR four times daily) for 5 days in women (7 days in men/complicated cystitis). Recurrent UTI Prophylaxis: 50 mg to 100 mg once daily at bedtime. Follow physician prescription.
Administration & Meal Timing: MUST be taken WITH FOOD or MILK! (Food delays gastric emptying, increasing oral bioavailability by ~40%, increasing peak urinary concentrations, and dramatically reducing nitrofurantoin-induced nausea!). | Twice daily with breakfast and dinner (for 100 mg SR/MR); at bedtime for prophylaxis.
6. Pharmacokinetics, Metabolism & Renal/Hepatic Adjustment
Absorption, distribution, metabolism, and excretion follow class pharmacokinetic profile; verify patient renal/hepatic function.
Renal: STRICTLY RENAL-FUNCTION DEPENDENT! Contraindicated if eGFR <30–45 mL/min (both ineffective in urine and toxic in blood!). Hepatic: Contraindicated in prior nitrofurantoin jaundice or chronic liver disease.
Renal: STRICTLY RENAL-FUNCTION DEPENDENT! Contraindicated if eGFR <30–45 mL/min (both ineffective in urine and toxic in blood!). Hepatic: Contraindicated in prior nitrofurantoin jaundice or chronic liver disease.
Renal: STRICTLY RENAL-FUNCTION DEPENDENT! Contraindicated if eGFR <30–45 mL/min (both ineffective in urine and toxic in blood!). Hepatic: Contraindicated in prior nitrofurantoin jaundice or chronic liver disease.
7. Contraindications, Precautions & High-Risk Warnings
- 1. STRICTLY CONTRAINDICATED IN RENAL IMPAIRMENT (CrCl / eGFR <45 mL/min [historically <60 mL/min; absolute contraindication <30–45 mL/min])! When GFR is low, nitrofurantoin fails to filter into the urine (so it cannot cure the UTI!) while accumulating in the bloodstream to cause severe peripheral neuropathy and toxicity! 2. Strictly contraindicated in G6PD Deficiency (causes acute intravascular haemolytic anaemia!), pregnancy at term (38–42 weeks) and neonates <1 month (neonatal haemolysis).
Key Clinical Precautions: Renal: STRICTLY RENAL-FUNCTION DEPENDENT! Contraindicated if eGFR <30–45 mL/min (both ineffective in urine and toxic in blood!). Hepatic: Contraindicated in prior nitrofurantoin jaundice or chronic liver disease.
8. Adverse Effects Profile
- Nausea, anorexia, epigastric discomfort (markedly reduced by taking with food and using 100 mg SR macrocrystal formulations), headache, flatulence, harmless dark yellow or rust-brown discolouration of urine.
- Acute and Chronic Nitrofurantoin Pulmonary Toxicity (Acute hypersensitivity pneumonitis within 1–2 weeks: fever, eosinophilia, dyspnoea, cough; Chronic interstitial pulmonary fibrosis with ≥6 months prophylaxis: insidious dry cough and progressive breathlessness in elderly women!), Sensorimotor Peripheral Neuropathy (glove-and-stocking numbness/burning, especially in CKD/elderly), autoimmune-like chronic active hepatitis/cholestasis, haemolytic anaemia in G6PD deficiency.
- Monitor for severe hypersensitivity, organ toxicity, or dose-limiting adverse events.
9. Major Drug–Drug, Drug–Food & Drug–Herb Interactions
- Magnesium Trisilicate Antacids adsorb nitrofurantoin on their surface, reducing absorption—avoid co-administration! Uricosuric drugs (Probenecid, Sulfinpyrazone) inhibit renal tubular secretion of nitrofurantoin, reducing urinary efficacy and increasing systemic toxicity
- Urinary Alkalinisers (Disodium Hydrogen Citrate syrups like Citralka / Cital / Alkacitra, often co-prescribed for burning urination!): Note that nitrofurantoin antibacterial activity is highest in acidic urine (pH <5
- 0); excessive urinary alkalinisation above pH 8 reduces nitrofurantoin bactericidal potency!
10. Clinical Monitoring, Patient Counselling & Storage
Clinical & Laboratory Monitoring: Monitor clinical response, baseline renal/hepatic parameters, and relevant serum biomarkers.
Pharmacist Patient Counselling Points:
- Patient Counselling Checklist: Always take Niftas/Martifur-MR with breakfast and dinner (never on an empty stomach). Reassure the patient that brownish-yellow urine is harmless. If the patient is an elderly woman put on daily night-time nitrofurantoin for months to prevent recurrent UTIs, warn her and her family to report any new dry cough or shortness of breath immediately.
- Meal & Clock Timing Instruction: MUST be taken WITH FOOD or MILK! (Food delays gastric emptying, increasing oral bioavailability by ~40%, increasing peak urinary concentrations, and dramatically reducing nitrofurantoin-induced nausea!). (Twice daily with breakfast and dinner (for 100 mg SR/MR); at bedtime for prophylaxis.)
- Missed Dose Protocol: Take with food as soon as remembered unless close to next scheduled dose.
- Geriatric Dispensing Pearl: Beers Criteria Precaution: Avoid nitrofurantoin in elderly patients with CrCl <30–45 mL/min, and avoid long-term suppressive prophylaxis (>6 months) in the elderly due to irreversible pulmonary fibrosis, hepatotoxicity, and peripheral neuropathy.
Storage, Stability & Dispensing Safeguards: Store below 25°C–30°C in original moisture- and light-resistant packaging out of reach of children. Available forms: Immediate-Release Tablets/Capsules: 50 mg, 100 mg; Sustained/Modified-Release (SR/MR) Tablets: 100 mg SR; Paediatric Suspension: 25 mg/5 mL
11. Visual Pharmacology & Mechanism Diagram (svg-v339-01-adme-12-step-journey)
12. Authoritative References, Regulatory Sources & Editorial Disclaimer
Primary Compendial & Guideline Reference: Indian Pharmacist Desk Reference — Professional Edition 2.7 (2026–27) • Ch 08 [8.12] (p. 98)
Official Verification Portals: Indian Pharmacopoeia Commission (IPC) & National Formulary of India (NFI) • Central Drugs Standard Control Organization (CDSCO) • Ministry of Health & Family Welfare — NLEM 2022 • NCBI Bookshelf / StatPearls Pharmacology Reference • DailyMed (US FDA Official Prescribing Reference)
Last Medically & Pharmaceutically Reviewed: 2026-11-10 • Verification Status: HANDBOOK_SOURCE_CONTENT
Educational & Clinical Disclaimer: This reference profile is published solely for pharmacy education, academic study, and professional clinical reference. It does not substitute for patient-specific clinical judgement, qualified specialist oncology/medical supervision, or official CDSCO/IP prescribing information. Never self-medicate with prescription, Schedule H/H1/X, NDPS, or oncology medicines.
13. Related Reference Monographs, Educational Guides & Visual Concept
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