Metronidazole
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Metronidazole
Flagyl, Metrocream, Metrogel, Metrogel-Vaginal, Noritate
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Summary
Common uses
Clostridioides difficile colitis (mild-moderate; alternative to vancomycin/fidaxomicin which are now preferred)0, Bacterial vaginosis0, Trichomoniasis0, Giardiasis0, Amebiasis0, Anaerobic bacterial infections (intra-abdominal, brain abscess, etc.)0, H. pylori eradication (combination)0, Rosacea (topical)0
Pharmacy
Starting dose
500 mg PO TID × 7-10 days (most indications); 2 g single dose for trichomoniasis; 500 mg IV q8h for severe anaerobic infection; rectal 1 g BID
Preparations
250, 500 mg tablets; 750 mg ER; 500 mg/100 mL IV; 0.75-1% topical gel/cream; 0.75% vaginal gel; suppository
US FDA Max
~4 g/d (severe systemic infection)
Pharmacology
Routes
Oral, IV, topical, vaginal
Onset
Hours
Duration
8-12 hours
Half-life
6-8 hours[1]
Bioavailability
~80% (oral)[1]
Pregnancy
Generally considered safe after the first trimester; first-trimester use weighed against indication.[citation needed]
Legal status
Rx-only in US
Purported mechanism
Metronidazole's nitro group is reduced by anaerobic bacterial and protozoal enzymes (ferredoxin or equivalent low-redox electron carriers) to reactive nitro radical anions that damage DNA via oxidative breaks; aerobic cells lack the requisite low-redox machinery and are spared, giving the drug its selectivity for anaerobes and microaerophiles.0 Disulfiram-like reaction with alcohol is the most-discussed but debated interaction (mechanism may be more about aldehyde dehydrogenase or 5-HT effects than true disulfiram). Peripheral neuropathy with prolonged use; rare CNS toxicity (cerebellar, encephalopathy) with high cumulative doses[1].
References
- ↑ 1.0 1.1 1.2 FDA Prescribing Information, Flagyl (metronidazole), Pfizer, current revision. https://www.accessdata.fda.gov/drugsatfda_docs/label/2018/012623s069lbl.pdf