BENZAMYCIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for BENZAMYCIN (BENZAMYCIN).
BENZAMYCIN (benzoyl peroxide and clindamycin) combines the keratolytic and antimicrobial actions of benzoyl peroxide with the antibacterial effect of clindamycin, a lincosamide antibiotic that inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit.
| Metabolism | Clindamycin is primarily metabolized by the liver to active and inactive metabolites, mainly via CYP3A4. Benzoyl peroxide is metabolized to benzoic acid, then conjugated with glycine to hippuric acid and excreted in urine. |
| Excretion | Renal excretion: ~70% (30% as unchanged drug, 40% as active metabolite N-desmethylclindamycin); biliary/fecal: ~30% |
| Half-life | 2.5-3.5 hours in adults with normal renal function; may be prolonged to 4-6 hours in patients with hepatic impairment |
| Protein binding | 90-94% bound primarily to albumin, with minor binding to alpha-1-acid glycoprotein |
| Volume of Distribution | 0.6-1.2 L/kg, indicating extensive tissue distribution; concentrates in bone, bile, and skin |
| Bioavailability | Oral: 85-90% (rapid and well absorbed); topical: 0.5-2% systemic absorption (minimal, but may accumulate with prolonged use on damaged skin) |
| Onset of Action | Oral: 45-60 minutes; topical: 2-6 hours for reduction of Propionibacterium acnes counts; clinical improvement may require 2-4 weeks |
| Duration of Action | Oral: 8-12 hours; topical: maintains antimicrobial effect for 12-24 hours; clinical effect sustained with continued use |
| Molecular Weight | 733.93 |
Topical: Apply a thin layer to affected areas twice daily (morning and evening). Each gram contains 30 mg benzoyl peroxide and 30 mg erythromycin.
| Dosage form | GEL |
| Renal impairment | No dosage adjustment required for renal impairment. |
| Liver impairment | No dosage adjustment required for hepatic impairment. |
| Pediatric use | Children ≥12 years: Apply topically twice daily. Safety and efficacy in children <12 years not established. |
| Geriatric use | No specific dosage adjustment needed; use with caution due to potential increased sensitivity. |
| 1st trimester | Avoid; risk of fetal harm based on animal studies and potential for interference with folate metabolism. |
| 2nd trimester | Avoid; benzamycin component may cause fetal harm; no adequate human studies. |
| 3rd trimester | Avoid; risk of kernicterus in newborn due to sulfonamide component. |
Clinical note
Comprehensive clinical and safety monograph for BENZAMYCIN (BENZAMYCIN).
| Placental transfer | Erythromycin crosses placenta to a limited extent; benzoyl peroxide is rapidly converted to benzoic acid which crosses placenta but significance unknown. |
| Breastfeeding | Benzamycin components (benzoyl peroxide and erythromycin) are minimally absorbed; however, erythromycin may be excreted in breast milk in small amounts, posing risk of infant gastrointestinal disturbance or alteration in gut flora. Use with caution or avoid. |
■ FDA Black Box Warning
Clindamycin component: Clostridioides difficile-associated diarrhea (CDAD) can occur with antibiotic use, ranging from mild diarrhea to fatal colitis.
| Serious Effects |
Hypersensitivity to benzoyl peroxide, erythromycin, or any componentConcurrent use of systemic retinoids or known history of pseudomembranous colitis
| Precautions | Avoid contact with eyes, mouth, lips, and mucous membranes; may bleach hair or fabric; use with caution in colitis; discontinue if diarrhea occurs; potential for antibiotic resistance with prolonged use. |
| Food/Dietary | No clinically significant food interactions. Take with or without food. No dietary restrictions. |
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| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | BENZAMYCIN (3% erythromycin/5% benzoyl peroxide) topical: No adequate studies in pregnant women. Animal studies not available for this combination. Erythromycin is generally considered low risk; benzoyl peroxide is poorly absorbed. Avoid in first trimester unless clearly needed. |
| Fetal Monitoring | No specific monitoring required due to minimal systemic absorption. Routine prenatal care sufficient. |
| Fertility Effects | No known effects on fertility from topical use. Systemic absorption is negligible. |
| Clinical Pearls |
| BENZAMYCIN (benzoyl peroxide 5% / clindamycin 1% gel) is a topical combination product for acne vulgaris. Avoid contact with eyes, mouth, and mucous membranes. May bleach hair or colored fabrics. Use only on skin; not for oral or ophthalmic use. Can cause skin dryness, peeling, or photosensitivity. Use with caution in patients with history of colitis; discontinue if diarrhea occurs due to rare risk of pseudomembranous colitis from clindamycin. |
| Patient Advice | Apply a thin layer to affected areas once or twice daily after washing. · Wash hands after application unless treating hands. · Avoid contact with eyes, lips, and inside nose or mouth. · May bleach hair or colored fabrics; avoid contact with clothing. · Use sunscreen and protective clothing to prevent sun sensitivity. · Do not use other topical acne products unless directed by your doctor. · Notify your doctor if you develop severe skin irritation or diarrhea. · Not for use in children under 12 years of age without medical advice. |