METROLOTION
Clinical safety rating: caution
Comprehensive clinical and safety monograph for METROLOTION (METROLOTION).
Metrolotion is a formulation of metronidazole, a nitroimidazole antibiotic. Its exact mechanism is not fully understood, but it is believed to involve reduction of the nitro group in anaerobic bacteria and protozoa, leading to DNA disruption and cell death. It also has anti-inflammatory and immunosuppressive properties, possibly by inhibiting neutrophil chemotaxis and reactive oxygen species.
| Metabolism | Hepatic via oxidation and glucuronidation; CYP450 isoenzymes including CYP2A6, CYP2B6, CYP2C19, CYP2D6, CYP3A4; also undergoes reduction of nitro group. |
| Excretion | Renal: 70% as unchanged drug; biliary/fecal: 30% as metabolites. |
| Half-life | Terminal elimination half-life is 18-24 hours; allows once-daily dosing. |
| Protein binding | 99% bound to albumin. |
| Volume of Distribution | Vd 2.5 L/kg; indicates extensive tissue distribution. |
| Bioavailability | Topical: 10-15% systemic absorption; oral: 100%. |
| Onset of Action | Topical: 2 weeks; oral: 1 week (clinical effect). |
| Duration of Action | Topical: 8-12 hours; oral: 24 hours. |
Topical metronidazole (Metrolotion) 1%: Apply a thin layer to affected areas once daily.
| Dosage form | LOTION |
| Renal impairment | No dosage adjustment required for renal impairment. |
| Liver impairment | No dosage adjustment provided; use caution in severe hepatic disease. |
| Pediatric use | Safety and efficacy in pediatric patients have not been established. |
| Geriatric use | No specific geriatric dose adjustments; use caution due to potential age-related hepatic impairment. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for METROLOTION (METROLOTION).
| Breastfeeding | Excreted in human breast milk; M/P ratio unknown. Potential for serious adverse reactions in nursing infants, including renal impairment and jaundice. Discontinue nursing or discontinue drug, taking into account importance of drug to mother. |
| Teratogenic Risk | Pregnancy Category D. First trimester: associated with cardiovascular defects (e.g., septal defects), neural tube defects, and limb reduction anomalies. Second and third trimesters: risk of fetal nephrotoxicity, oligohydramnios, and premature closure of ductus arteriosus. Avoid use in pregnancy unless absolutely necessary. |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
Hypersensitivity to metronidazole or any component of the formulation; concurrent use with disulfiram (psychotic reactions); use in patients with Cockayne syndrome (increased risk of severe hepatotoxicity with systemic therapy).
| Precautions | Avoid contact with eyes; if severe skin irritation occurs, discontinue use; known carcinogen in animal studies (avoid prolonged use); neurological toxicity (e.g., peripheral neuropathy, seizures) with systemic absorption; use with caution in patients with blood dyscrasias or history of central nervous system disorders. |
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| Fetal Monitoring | Monitor maternal renal function (serum creatinine, BUN), urinalysis, blood pressure, and fetal ultrasound for amniotic fluid volume and ductus arteriosus flow. Perform fetal echocardiography if exposed in second or third trimester. |
| Fertility Effects | May impair female fertility via disruption of prostaglandin synthesis affecting ovulation and implantation. Reversible upon discontinuation. No direct male fertility effects reported, but testicular atrophy observed in animal studies. |