Nitrofurantoin
Nitrofurantoin
Macrobid (monohydrate/macrocrystals), Macrodantin (macrocrystals), Furadantin (suspension)
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Summary
Common uses
Uncomplicated lower UTI0, UTI prophylaxis (chronic suppression)0
Pharmacy
Starting dose
100 mg PO BID × 5 days (Macrobid) for cystitis; 50-100 mg HS for chronic prophylaxis
Preparations
25 mg/5 mL suspension; 25, 50, 100 mg capsules (Macrodantin); 100 mg Macrobid capsule
US FDA Max
400 mg/d (rarely used)
Pharmacology
Routes
Oral
Onset
Urinary concentration adequate within hours
Duration
12 hours (Macrobid)
Half-life
~20-60 minutes (plasma; not the relevant kinetic since urinary concentration matters)[1]
Bioavailability
~90% (oral; food increases absorption)[1]
Pregnancy
Avoid at term (38-42 weeks) and during labor (risk of neonatal hemolytic anemia, especially with G6PD deficiency); generally safe in earlier pregnancy.[citation needed]
Legal status
Rx-only in US
Purported mechanism
Nitrofurantoin is reduced by bacterial flavoproteins to reactive intermediates that damage bacterial ribosomal proteins, DNA, and metabolic enzymes; the multiplicity of targets contributes to the historically low resistance rate. Therapeutic concentrations are achieved only in urine, restricting use to lower urinary tract infections.0 Avoid in CrCl <30 mL/min (inadequate urinary levels, increased systemic toxicity). Pulmonary toxicity (acute hypersensitivity pneumonitis; chronic interstitial fibrosis with long-term prophylaxis) and peripheral neuropathy are the most serious adverse effects[1].
References
- ↑ 1.0 1.1 1.2 FDA Prescribing Information, Macrobid (nitrofurantoin monohydrate/macrocrystals), Almatica Pharma, current revision. https://www.accessdata.fda.gov/drugsatfda_docs/label/2018/020064s029lbl.pdf