METROGEL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for METROGEL (METROGEL).
Metronidazole, after intracellular reduction, forms cytotoxic metabolites that disrupt bacterial DNA and inhibit nucleic acid synthesis. It also has anti-inflammatory and immunomodulatory effects in rosacea.
| Metabolism | Hepatic via glucuronidation and oxidation; metabolites excreted renally. |
| Excretion | Renal: 60-80% as unchanged drug; fecal: 6-15%; biliary: minor. |
| Half-life | 8-10 hours (terminal); increased to 20-30 hours in hepatic impairment. |
| Protein binding | Less than 20%; albumin. |
| Volume of Distribution | 0.25-0.85 L/kg; extensive tissue distribution including CSF. |
| Bioavailability | Topical: minimal systemic absorption (2-4%); oral: 80-100%; intravenous: 100%. |
| Onset of Action | Topical: 2-3 weeks for rosacea improvement; intravenous: immediate for bacterial infections. |
| Duration of Action | Topical: continuous use required; intravenous: dosing every 6-8 hours (half-life dependent). |
Topical application of 1% gel: Apply a thin layer to affected area twice daily; intravaginal 0.75% gel: one applicatorful (5 g) once daily at bedtime.
| Dosage form | GEL |
| Renal impairment | No dose adjustment required for topical or intravaginal use; systemic absorption is minimal. |
| Liver impairment | No dose adjustment required; use with caution in severe hepatic impairment due to potential for increased systemic exposure. |
| Pediatric use | Topical 1% gel: apply twice daily for children ≥12 years; safety and efficacy for rosacea in children <12 not established. |
| Geriatric use | No specific dose adjustment; use same dosing as adults; monitor for local adverse effects due to thinner skin. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for METROGEL (METROGEL).
| Breastfeeding | Excreted in breast milk; M/P ratio ~1.0; American Academy of Pediatrics considers compatible; delay breastfeeding 12-24h after IV dose. |
| Teratogenic Risk | Metronidazole crosses the placenta. First trimester: avoid unless essential; second/third trimester: no increased risk of major malformations in large cohort studies; potential neurodevelopmental risks unclear. |
| Fetal Monitoring |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
Hypersensitivity to metronidazole or any component of the formulation; concurrent disulfiram use; history of alcoholic beverage consumption during therapy.
| Precautions | Avoid unnecessary prolonged use; may cause peripheral neuropathy with chronic use; discontinue if neurological symptoms occur; photosensitivity reactions; avoid sun exposure. |
Loading safety data…
| None routine; monitor for maternal adverse effects (GI, neurotoxicity); fetal monitoring only if maternal toxicity. |
| Fertility Effects | No known adverse effects on fertility or reproduction. |