metronidazole: prescribing and clinical use
Focused clinical detail for use alongside current product information, local policy and patient-specific assessment.
metronidazole: clinical details
Prescribing considerations
- Confirm that the likely pathogen and infection site are appropriate for anaerobic or protozoal cover; metronidazole does not treat aerobic organisms alone.
- Consider hepatic impairment, active neurological disease, seizure history, blood disorders and important interacting medicines.
- Avoid unnecessary prolonged or repeated systemic exposure; investigate new neurological, haematological or hepatic symptoms.
- Selected infusion products contain sodium.
- Topical rosacea formulations have much lower systemic exposure than oral or intravenous formulations.
Contraindications and cautions
- Hypersensitivity to metronidazole, other nitroimidazoles or formulation excipients.
- Selected topical products contraindicate use in Cockayne syndrome because severe hepatotoxicity and acute liver failure have been reported.
Monitoring
- Review liver function where hepatic risk is increased and promptly if symptoms of liver injury develop.
- For prolonged or repeated systemic treatment, consider blood counts and monitor for peripheral or central neurotoxicity.
- Monitor INR or prothrombin time with warfarin-type anticoagulants.
- With lithium, monitor lithium concentration, renal function and electrolytes if concurrent use cannot be avoided.
Clinical pharmacology
Metronidazole undergoes intracellular reduction in susceptible anaerobes and protozoa, generating intermediates that disrupt DNA. Topical systemic exposure is substantially lower.
Formulation and product differences
- Tablets provide systemic treatment and should not be substituted by topical products.
- Intravenous solutions are intended for hospital use; selected products differ in sodium content and preparation instructions.
- Selected creams and gels are licensed for rosacea and differ in vehicle and excipients, which may affect local tolerability.
metronidazole preparations and strengths
Cream
Route: Cutaneous
Strengths: 0.75% w/w
Gel
Route: Cutaneous
Strengths: 0.75% w/w
Solution for infusion
Route: Intravenous
Strengths: 500 mg/100 mL
Tablet
Route: Oral
Strengths: 200 mg, 400 mg, 500 mg
metronidazole interactions
Interactions are generally more important with systemic formulations because absorption from skin products is low.
Alcohol and alcohol-containing products
May cause nausea, flushing, abdominal pain, headache, breathlessness or palpitations; avoid during systemic treatment and for two days afterwards.
Warfarin and related anticoagulants
Anticoagulant effects can increase, so clotting tests and anticoagulant management may need review.
Lithium
Lithium concentrations and toxicity may increase; specialist review and laboratory monitoring may be required.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.