TERRAMYCIN W/ POLYMYXIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TERRAMYCIN W/ POLYMYXIN (TERRAMYCIN W/ POLYMYXIN).
Terramycin (oxytetracycline) is a bacteriostatic tetracycline antibiotic that inhibits protein synthesis by binding to the 30S ribosomal subunit, preventing aminoacyl-tRNA binding. Polymyxin B is a cationic polypeptide that disrupts bacterial cell membranes by interacting with lipopolysaccharides in Gram-negative bacteria.
| Metabolism | Not extensively metabolized; primarily excreted unchanged in urine and feces. |
| Excretion | Renal: Oxytetracycline ~70% unchanged; Polymyxin B ~60% unchanged. Fecal: Oxytetracycline ~20-30% (biliary and unabsorbed); Polymyxin B ~40% (biliary). |
| Half-life | Oxytetracycline: 6-10 hours (normal renal function; prolonged to 50-100 hours in anuria). Polymyxin B: 6-8 hours (normal renal function; prolonged to 24-48 hours in renal impairment). |
| Protein binding | Oxytetracycline: 20-35% (bound to albumin). Polymyxin B: ~80% (bound to plasma proteins, including albumin). |
| Volume of Distribution | Oxytetracycline: 0.9-1.4 L/kg (distributes widely, except CSF). Polymyxin B: 0.5-1.0 L/kg (mostly extracellular, limited CNS penetration). |
| Bioavailability | IM: Oxytetracycline ~100% (aqueous solution); Polymyxin B ~100% (IM). Oral: Not applicable (polymyxin B not absorbed; oxytetracycline ~70-80% oral but not in this product). Topical: Minimal systemic absorption. |
| Onset of Action | IM: Oxytetracycline peaks in 1-2 hours; Polymyxin B peaks in 1-2 hours. Topical: Local antimicrobial effect within hours. |
| Duration of Action | Oxytetracycline: 12-24 hours (dosing q12h for systemic infections). Polymyxin B: 8-12 hours (dosing q12h). Topical: Varies; typical q6-12h application. |
Not applicable: Terramycin (oxytetracycline) and polymyxin B combination is not available for systemic use; topical or ophthalmic preparations only; no standard adult systemic dose.
| Dosage form | OINTMENT |
| Renal impairment | Not applicable: No systemic dosing; topical use does not require adjustment. |
| Liver impairment | Not applicable: No systemic dosing; contraindicated in severe hepatic impairment if systemic absorption occurs (e.g., extensive burns). |
| Pediatric use | Not applicable: Safety and efficacy not established; contraindicated in children <8 years due to teeth discoloration and bone growth retardation. |
| Geriatric use | Not applicable: No systemic dosing; use with caution if renal impairment present due to potential nephrotoxicity from polymyxin B with topical application on denuded skin. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for TERRAMYCIN W/ POLYMYXIN (TERRAMYCIN W/ POLYMYXIN).
| Breastfeeding | Oxytetracycline is excreted in breast milk in low concentrations (M/P ratio not established for this specific combination). Potential for bone and dental effects in the nursing infant. Polymyxin B is poorly absorbed orally, so infant exposure likely negligible. Caution advised: consider alternative antibiotics during breastfeeding. |
| Teratogenic Risk | Tetracyclines (oxytetracycline) cross the placenta. First trimester: limited evidence of teratogenicity, but use generally avoided due to risk of neural tube defects? Second/third trimester: use contraindicated due to risk of permanent tooth discoloration and enamel hypoplasia in the fetus; also associated with reversible inhibition of fetal bone growth. Polymyxin B: minimal placental transfer; no known teratogenicity in animal studies. Combined product: avoid in pregnancy unless no alternative. |
■ FDA Black Box Warning
No FDA black box warning for this combination product.
| Serious Effects |
["Hypersensitivity to any component","Myasthenia gravis (due to polymyxin B)","Avoid in otic use if tympanic membrane is perforated"]
| Precautions | ["Hypersensitivity reactions including anaphylaxis","Photosensitivity with oxytetracycline","Nephrotoxicity with polymyxin B","Neuromuscular blockade with polymyxin B","Avoid prolonged use","Monitor renal function"] |
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| Fetal Monitoring | Monitor maternal renal and hepatic function periodically. Observe infant for signs of photosensitivity, gastrointestinal disturbances, or superinfection. In prolonged maternal use, monitor infant for potential effects on bone and dental development. |
| Fertility Effects | Tetracyclines may impair fertility in animal studies; human data insufficient. Reversible inhibition of spermatogenesis reported in some cases. No specific data on polymyxin B. No known effect on female fertility. |