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. |
| Molecular Weight | Oxytetracycline (main component) molecular weight = 460.43 g/mol |
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 | Avoid. Tetracyclines cross placenta and cause permanent tooth discoloration and inhibit bone growth. Risk of teratogenicity (neural tube defects) with first-trimester exposure. |
| 2nd trimester | Avoid. Use only if no alternative and infection severe. Risk of maternal hepatotoxicity and fetal skeletal abnormalities. |
| 3rd trimester | Contraindicated. Risk of fetal tooth discoloration, enamel hypoplasia, and bone growth retardation. Also associated with maternal fatty liver. |
Clinical note
Comprehensive clinical and safety monograph for TERRAMYCIN W/ POLYMYXIN (TERRAMYCIN W/ POLYMYXIN).
| Placental transfer | Extensive: tetracyclines cross placenta rapidly, achieving fetal serum concentrations 50-100% of maternal levels. Polymyxin B crosses minimally. |
| Breastfeeding | Tetracyclines are excreted in breast milk in low amounts but may cause dental staining and bone suppression in nursing infants. Avoid or use alternative if possible. Polymyxin B is poorly absorbed orally, unlikely to cause systemic effects. |
■ FDA Black Box Warning
No FDA black box warning for this combination product.
| Serious Effects |
Hypersensitivity to tetracyclines or polymyxinsPregnancy (especially second and third trimesters)Breastfeeding (relative, avoid if possible)Children under 8 years (risk of tooth discoloration and bone growth inhibition)Severe hepatic impairment (tetracycline hepatotoxicity risk)Myasthenia gravis (polymyxin B may cause neuromuscular blockade)
| Precautions | Hypersensitivity reactions including anaphylaxis, Photosensitivity with oxytetracycline, Nephrotoxicity with polymyxin B, Neuromuscular blockade with polymyxin B, Avoid prolonged use, Monitor renal function |
| Food/Dietary | No known food interactions with topical ophthalmic Terramycin with polymyxin B. Systemic absorption is negligible. No dietary restrictions required. |
Loading safety data…
| Lactation Rating | L3 - Moderately Safe (use with caution, monitor infant for gastrointestinal disturbance and rash) |
| 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. |
| 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. |
| Clinical Pearls | Terramycin (oxytetracycline) with polymyxin B is a combination ophthalmic ointment used for superficial ocular infections. Oxytetracycline is a bacteriostatic tetracycline inhibiting protein synthesis; polymyxin B is a bactericidal polypeptide disrupting cell membranes. Efficacy covers Gram-positive (Staphylococcus, Streptococcus) and Gram-negative (Pseudomonas, E. coli) pathogens. Avoid prolonged use due to risk of superinfection. Do not use for viral or fungal infections. In patients with renal impairment, monitor for cumulative toxicity from polymyxin B. Discontinue if hypersensitivity or corneal epithelial defects occur. This formulation is not for injection or systemic use. |
| Patient Advice | Wash hands before and after application. · Tilt head back, pull down lower eyelid, and apply a small strip (about 0.5-1 cm) of ointment into the conjunctival sac. · Do not touch the tube tip to any surface, including the eye, to avoid contamination. · Blurred vision may occur temporarily after application; avoid driving or operating machinery until vision clears. · Complete the full course of treatment even if symptoms improve; do not skip doses. · Do not use for longer than prescribed to reduce risk of antibiotic resistance. · Notify your doctor if symptoms worsen or do not improve within a few days. · Remove contact lenses before application; do not wear during treatment unless directed. · Store the ointment at room temperature, away from heat and direct sunlight. · Keep out of reach of children. |