Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
BACITRACIN-NEOMYCIN-POLYMYXIN W/ HYDROCORTISONE ACETATE vs BETHKIS
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Bacitracin inhibits bacterial cell wall synthesis by interfering with dephosphorylation of the peptidoglycan carrier lipid; neomycin binds to 30S ribosomal subunit causing misreading of m RNA; polymyxin B disrupts bacterial cell membrane permeability via interaction with phospholipids; hydrocortisone acetate suppresses inflammation by inhibiting phospholipase A2, reducing prostaglandin and leukotriene synthesis.
Tobramycin, an aminoglycoside antibiotic, binds to the 30S ribosomal subunit, causing misreading of m RNA and inhibiting protein synthesis, leading to bacterial cell death.
Treatment of superficial ocular infections caused by susceptible organisms,Reduction of inflammation in corticosteroid-responsive ocular conditions,Off-label: treatment of otitis externa (otic preparations)
Management of cystic fibrosis patients with Pseudomonas aeruginosa infection
Apply a thin layer to the affected area 3-4 times daily. Ophthalmic: Instill 1-2 drops into the affected eye(s) every 3-4 hours, or more frequently if needed. Otic: Instill 4 drops into the affected ear(s) 3-4 times daily.
4 IU/kg (1 mg/kg) intramuscularly or subcutaneously once weekly for 4 weeks, then a maintenance dose of 2 IU/kg (0.5 mg/kg) once weekly.
Bacitracin: 1.5 h (systemic) but clinically irrelevant as topical. Neomycin: 2-3 h (systemic). Polymyxin B: 4.5-6 h (systemic). Hydrocortisone acetate: 1.5-2.5 h (plasma); clinical effect outlasts serum half-life due to intracellular activity.
Terminal elimination half-life 2-3 hours in patients with normal renal function; prolonged to 20-40 hours in severe renal impairment (Cr Cl <30 m L/min).
Bacitracin: not metabolized, excreted renally; neomycin: minimally metabolized, excreted renally; polymyxin B: metabolism unknown, excreted renally; hydrocortisone acetate: hepatic metabolism via CYP3A4, glucuronidation, sulfation.
Primarily excreted unchanged in urine via glomerular filtration; minimal hepatic metabolism.
Bacitracin: renal (minimal systemic absorption; eliminated unchanged in urine if absorbed). Neomycin: renal (90-95% excreted unchanged in urine after systemic absorption). Polymyxin B: renal (60% excreted unchanged over 24h; prolonged elimination in renal impairment). Hydrocortisone acetate: hepatic metabolism (glucuronidation, sulfation) and renal excretion of metabolites.
Primarily renal excretion of unchanged drug via glomerular filtration; ~90% of absorbed dose excreted in urine within 24 hours; biliary/fecal elimination <5%.
Bacitracin: ~10% (albumin). Neomycin: <30% (albumin). Polymyxin B: 55-60% (albumin, alpha-1-acid glycoprotein). Hydrocortisone acetate: 90-95% (corticosteroid-binding globulin, albumin).
Low protein binding: 10-20%; primarily binds to albumin.
Bacitracin: 0.3 L/kg (minimal distribution). Neomycin: 0.2-0.4 L/kg (extracellular fluid). Polymyxin B: 0.6-0.8 L/kg (extensively bound to cell membranes). Hydrocortisone acetate: 0.3-0.6 L/kg (total body water).
0.2-0.4 L/kg; distributes primarily into extracellular fluid; limited intracellular penetration.
Topical/otic/ophthalmic: negligible systemic absorption (<1% for bacitracin, neomycin, polymyxin B; <5% for hydrocortisone acetate). Oral: not applicable (not administered systemically).
Inhalation: ~50-60% of nominal dose reaches systemic circulation; oral: negligible (<1% due to poor gastrointestinal absorption).
No systemic absorption anticipated with topical, ophthalmic, or otic use; however, for extensive topical application, caution in renal impairment due to neomycin and polymyxin B. GFR <30 m L/min: monitor for nephrotoxicity; reduce frequency if topical use over large areas.
No dose adjustment required for renal impairment. Not removed by hemodialysis.
No specific adjustment required for topical, ophthalmic, or otic use. Hydrocortisone acetate is hepatically metabolized; however, systemic exposure is minimal. Child-Pugh Class C: use with caution if applied to large areas or broken skin.
No dose adjustment recommended for mild to moderate hepatic impairment (Child-Pugh A or B). Use with caution in severe hepatic impairment (Child-Pugh C) due to lack of data.
Children: Apply a thin layer to affected area 3-4 times daily. Ophthalmic: Use same as adult dose. Otic: Infants and children: 3 drops into affected ear(s) 3-4 times daily. Safety and efficacy in neonates not established.
Weight-based dosing: 4 IU/kg (1 mg/kg) intramuscularly or subcutaneously once weekly for 4 weeks, then 2 IU/kg (0.5 mg/kg) once weekly. Safety and efficacy in children <18 years not established.
No specific dose adjustment required. Use with caution in elderly with impaired renal or hepatic function, especially if applied to large areas. Monitor for skin atrophy and systemic effects of hydrocortisone with prolonged use.
No specific dose adjustments recommended. Use with caution due to potential age-related decline in renal and hepatic function. Monitor for adverse effects.
None.
Risk of nephrotoxicity and ototoxicity; monitor renal function and hearing during therapy.
Prolonged use may lead to secondary infections (e.g., fungal) or hypersensitivity; ophthalmic use may cause increased intraocular pressure, cataract formation, and delayed wound healing; avoid use in patients with epithelial herpes simplex keratitis; systemic absorption may cause nephrotoxicity and ototoxicity (especially neomycin); use with caution in hepatic impairment.
Nephrotoxicity, ototoxicity (vestibular and auditory), neuromuscular blockade, hypersensitivity, superinfection.
Hypersensitivity to any component; ocular tuberculosis, viral infections of the cornea (e.g., herpes simplex keratitis), fungal diseases of the eye; untreated purulent infections; use in ears with tympanic membrane perforation (otic preparations).
Hypersensitivity to tobramycin or other aminoglycosides.
No significant food interactions. No dietary restrictions required.
No specific food interactions. Maintain adequate hydration; avoid excessive salt intake if concurrent diuretics are used.
Teratogenic risk is minimal due to negligible systemic absorption from topical application. No studies report fetal harm from bacitracin, neomycin, polymyxin B, or hydrocortisone acetate when used topically. Avoid prolonged use of high-dose hydrocortisone during first trimester due to potential corticosteroid effects.
Insufficient human data; animal studies show no teratogenic effects at doses up to 4 times the human dose. Risk cannot be ruled out; use only if clearly needed.
Systemic absorption is minimal; topical application likely poses low risk to nursing infant. M/P ratio not established for the combination. Avoid application to breast area to prevent infant ingestion.
Unknown if excreted in human breast milk; M/P ratio not available. Caution advised due to risk of infant bowel flora alteration and potential for tobramycin-related ototoxicity or nephropathy.
No dose adjustment required for topical application during pregnancy. Use sparingly on limited areas to minimize systemic absorption.
No specific dose adjustments recommended; pharmacokinetics may be altered due to increased volume of distribution and GFR; monitor serum levels and adjust to maintain therapeutic trough <2 mcg/m L.
This combination product is used for otitis externa and certain ophthalmic infections. The hydrocortisone reduces inflammation, but can mask signs of fungal or viral superinfection. Avoid use in patients with tympanic membrane perforation due to risk of ototoxicity from neomycin and polymyxin B. Neomycin carries sensitization risk; prolonged use may cause contact dermatitis. Monitor for overgrowth of non-susceptible organisms when used beyond 10 days.
Administer via inhalation only using a suitable nebulizer; do not mix with other drugs in the nebulizer. Monitor for bronchospasm; consider pretreatment with a bronchodilator in patients with reactive airway disease. Assess renal function before and during therapy due to potential nephrotoxicity. Obtain audiometric testing at baseline and periodically due to ototoxicity risk. Avoid concurrent use of loop diuretics or other nephrotoxic drugs. Trough serum tobramycin concentrations should be measured after 2–3 doses when systemic absorption is suspected.
Use exactly as prescribed; do not exceed recommended duration.,Avoid contact with eyes unless specifically directed for ophthalmic use.,Do not use if you have a perforated eardrum or ear discharge.,Stop use and notify your doctor if symptoms worsen or persist after 10 days.,Inform your doctor if you experience new pain, redness, or swelling.,Keep this medication out of reach of children.
Use Bethkis exactly as prescribed; do not skip doses or double up.,Do not swallow or inject Bethkis; it is for inhalation only.,Use a nebulizer with a mouthpiece; do not use a face mask unless necessary.,Store vials in the refrigerator; protect from light.,Clean and disinfect the nebulizer after each use.,Report hearing loss, ringing in the ears, dizziness, or changes in urine output immediately.,Avoid other inhaled medications within 30 minutes of Bethkis unless directed.,Inform your healthcare provider of all other medications, especially diuretics and other antibiotics.
"Hydrocortisone, a corticosteroid, may inhibit the hepatic metabolism of doxycycline, a tetracycline antibiotic, leading to increased doxycycline plasma concentrations. This elevation can potentiate doxycycline's adverse effects, such as gastrointestinal disturbance, photosensitivity, and hepatotoxicity. Clinically, this interaction may reduce the therapeutic window of doxycycline, requiring dose adjustment or alternative therapy selection."
"Fluconazole, a potent inhibitor of cytochrome P450 3A4 (CYP3A4), can significantly reduce the hepatic clearance of hydrocortisone, a corticosteroid metabolized primarily by CYP3A4. This interaction leads to increased systemic exposure to hydrocortisone, potentially resulting in exaggerated corticosteroid effects such as hyperglycemia, immunosuppression, and adrenal suppression. Clinically, patients may experience symptoms of Cushing's syndrome or require dose adjustments to avoid toxicity."
"Rifaximin, a non-systemic antibiotic primarily acting in the gastrointestinal tract, may inhibit intestinal P-glycoprotein (P-gp), reducing the efflux of corticosteroids like hydrocortisone. This can lead to increased systemic absorption and elevated serum concentrations of hydrocortisone, potentially enhancing both therapeutic and adverse effects such as hyperglycemia, immunosuppression, and adrenal suppression."
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about BACITRACIN-NEOMYCIN-POLYMYXIN W/ HYDROCORTISONE ACETATE vs BETHKIS, answered by our medical review team.
BACITRACIN-NEOMYCIN-POLYMYXIN W/ HYDROCORTISONE ACETATE is a Aminoglycoside Antibiotic that works by Bacitracin inhibits bacterial cell wall synthesis by interfering with dephosphorylation of the peptidoglycan carrier lipid; neomycin binds to 30S ribosomal subunit causing misreading of m RNA; polymyxin B disrupts bacterial cell membrane permeability via interaction with phospholipids; hydrocortisone acetate suppresses inflammation by inhibiting phospholipase A2, reducing prostaglandin and leukotriene synthesis.. BETHKIS is a Aminoglycoside Antibiotic that works by Tobramycin, an aminoglycoside antibiotic, binds to the 30S ribosomal subunit, causing misreading of m RNA and inhibiting protein synthesis, leading to bacterial cell death.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between BACITRACIN-NEOMYCIN-POLYMYXIN W/ HYDROCORTISONE ACETATE and BETHKIS depend on the specific clinical indication. These are both Aminoglycoside Antibiotic agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of BACITRACIN-NEOMYCIN-POLYMYXIN W/ HYDROCORTISONE ACETATE is: Apply a thin layer to the affected area 3-4 times daily. Ophthalmic: Instill 1-2 drops into the affected eye(s) every 3-4 hours, or more frequently if needed. Otic: Instill 4 drops into the affected ear(s) 3-4 times daily.. The standard adult dose of BETHKIS is: 4 IU/kg (1 mg/kg) intramuscularly or subcutaneously once weekly for 4 weeks, then a maintenance dose of 2 IU/kg (0.5 mg/kg) once weekly.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between BACITRACIN-NEOMYCIN-POLYMYXIN W/ HYDROCORTISONE ACETATE and BETHKIS in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. BACITRACIN-NEOMYCIN-POLYMYXIN W/ HYDROCORTISONE ACETATE is classified as Category A/B. Teratogenic risk is minimal due to negligible systemic absorption from topical application. No studies report fetal harm from bacitracin, neomycin, polymyxin B, or hydrocortisone a. BETHKIS is classified as Category C. Insufficient human data; animal studies show no teratogenic effects at doses up to 4 times the human dose. Risk cannot be ruled out; use only if clearly needed.. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.