MYCITRACIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MYCITRACIN (MYCITRACIN).
MYCITRACIN is a combination of bacitracin and neomycin, which are aminoglycoside antibiotics. Bacitracin inhibits bacterial cell wall synthesis by interfering with dephosphorylation of the lipid carrier that transports peptidoglycan subunits. Neomycin binds to the 30S ribosomal subunit, causing misreading of mRNA and inhibition of protein synthesis.
| Metabolism | Not systemically absorbed to a significant extent after topical application. If absorbed, neomycin is excreted primarily unchanged by the kidneys. |
| Excretion | Primarily renal (glomerular filtration and tubular secretion); >90% of dose excreted unchanged in urine within 24 hours. Biliary/fecal excretion is minimal (<5%). |
| Half-life | Terminal elimination half-life is 2–3 hours in adults with normal renal function. Prolonged significantly in renal impairment (up to 24–48 hours in anuria). |
| Protein binding | Approximately 30% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | 0.2–0.4 L/kg, indicating distribution primarily into extracellular fluid; does not penetrate cells or the CNS significantly. |
| Bioavailability | Intramuscular: ~90%; Oral: <1% (not absorbed systemically; used for gut decontamination). |
| Onset of Action | Intramuscular: 30–60 minutes; Intravenous: immediate; Intraperitoneal: rapid (within minutes); Oral: not absorbed systemically (remains in GI tract). |
| Duration of Action | Intramuscular: 6–8 hours; Intravenous: 4–6 hours. Duration prolonged in renal dysfunction. |
500 mg orally every 6 hours
| Dosage form | OINTMENT |
| Renal impairment | GFR 30-50 mL/min: 500 mg every 8 hours; GFR 10-29 mL/min: 500 mg every 12 hours; GFR <10 mL/min: 500 mg every 24 hours |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: 500 mg every 8 hours; Child-Pugh C: use with caution, consider 500 mg every 12 hours |
| Pediatric use | 10-15 mg/kg/dose orally every 6 hours, maximum 500 mg per dose |
| Geriatric use | Use with caution; monitor renal function; adjust dose based on creatinine clearance; start at lower end of dosing range |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for MYCITRACIN (MYCITRACIN).
| Breastfeeding | Systemic absorption is minimal after topical application. No data on excretion in human milk. M/P ratio not determined. Likely compatible with breastfeeding if applied to small areas. Avoid application to breast area to prevent infant ingestion. |
| Teratogenic Risk | Mycitracin (bacitracin, neomycin, polymyxin B) topical use has minimal systemic absorption, thus teratogenic risk is low. No adequate studies in pregnant women; animal studies not reported. First trimester: theoretical risk from systemic absorption unlikely. Second and third trimesters: considered safe for topical use. Avoid on large areas, broken skin, or prolonged use. |
■ FDA Black Box Warning
Contains neomycin, which can cause nephrotoxicity and ototoxicity, especially with prolonged use or application to large areas of damaged skin. Risk is increased in patients with renal impairment.
| Serious Effects |
Hypersensitivity to bacitracin, neomycin, or any component of the formulation. Avoid in patients with pre-existing renal impairment or hearing loss.
| Precautions | Avoid use on large areas of broken skin or prolonged use due to risk of systemic absorption and toxicity. Monitor for signs of renal toxicity and ototoxicity. May cause allergic contact dermatitis. Use caution in patients with renal impairment. |
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| Fetal Monitoring | No specific monitoring required due to negligible systemic absorption. For extensive use or in renal impairment, monitor for nephrotoxicity and ototoxicity (from neomycin and polymyxin B) via serum creatinine and auditory tests. |
| Fertility Effects | No known effect on fertility. Animal studies not conducted. Systemic absorption unlikely, so no anticipated impact on reproductive function. |