ERYTHROMYCIN AND BENZOYL PEROXIDE
Clinical safety rating: safe
Inhibits CYP3A4 increasing levels of many drugs (eg statins carbamazepine) May cause QT prolongation and subsequent arrhythmias.
Erythromycin is a macrolide antibiotic that acts by binding to the 50S ribosomal subunit of susceptible bacteria, inhibiting protein synthesis. Benzoyl peroxide has bactericidal effects against Propionibacterium acnes, likely through the release of free radical oxygen that oxidizes bacterial proteins. It also has keratolytic and comedolytic properties.
| Metabolism | Erythromycin is partially metabolized via demethylation in the liver, primarily by CYP3A4. Benzoyl peroxide is metabolized in the skin to benzoic acid, which is then excreted renally. |
| Excretion | Erythromycin is primarily excreted via bile (fecal elimination) with approximately 15% excreted unchanged in urine. Benzoyl peroxide is degraded to benzoic acid, which is conjugated with glycine to form hippuric acid and excreted renally; less than 5% is excreted unchanged in urine. |
| Half-life | Erythromycin: 1.4–2.0 hours (terminal half-life in adults). Benzoyl peroxide: Not applicable; it is a topical agent with negligible systemic absorption. |
| Protein binding | Erythromycin: 70–90% bound, primarily to albumin. Benzoyl peroxide: Not applicable; topical absorption is minimal (<5%). |
| Volume of Distribution | Erythromycin: Vd = 0.4–0.6 L/kg, indicating distribution into total body water. Benzoyl peroxide: Not applicable due to minimal systemic absorption. |
| Bioavailability | Erythromycin base: 35–45% (oral). Benzoyl peroxide: <5% systemically absorbed after topical application. |
| Onset of Action | Topical: Clinical improvement in acne vulgaris typically seen within 2–4 weeks of regular application. |
| Duration of Action | Topical: Effect lasts 8–12 hours; requires twice-daily application for sustained efficacy. |
Topical: Apply a thin layer to affected areas once daily in the evening.
| Dosage form | GEL |
| Renal impairment | No adjustment required for topical use; systemic absorption is negligible. |
| Liver impairment | No adjustment required for topical use; systemic absorption is negligible. |
| Pediatric use | Approved for adolescents ≥12 years: same as adult dose. For children <12 years, safety and efficacy not established. |
| Geriatric use | No specific dose adjustment; use with caution due to potential for increased skin sensitivity or dryness. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Inhibits CYP3A4 increasing levels of many drugs (eg statins carbamazepine) May cause QT prolongation and subsequent arrhythmias.
| FDA category | Human |
| Breastfeeding | Erythromycin is excreted into breast milk in small amounts (M/P ratio not specifically reported for this combination). Benzoyl peroxide is not absorbed systemically. Risk to infant considered low; however, caution advised due to potential gastrointestinal effects from erythromycin. |
| Teratogenic Risk |
■ FDA Black Box Warning
None
| Common Effects | Nausea |
| Serious Effects |
["Hypersensitivity to erythromycin, benzoyl peroxide, or any component of the formulation"]
| Precautions | ["Avoid contact with eyes, mouth, and mucous membranes","May cause skin irritation, dryness, or peeling","Photosensitivity may occur with benzoyl peroxide","Antibiotic resistance with prolonged use","May stain clothing or hair"] |
Loading safety data…
| No evidence of teratogenicity in animal studies for erythromycin. For benzoyl peroxide, limited data but no known teratogenicity. Insufficient human data for combination. Risk cannot be excluded; use only if clearly needed. |
| Fetal Monitoring | No specific monitoring required beyond standard prenatal care. Observe for maternal skin irritation or allergic reaction; fetal effects not established. |
| Fertility Effects | No known effect on fertility from erythromycin or benzoyl peroxide. No human studies on combination. |