Neosporin - Drug Monograph

Introduction

Neosporin is a widely available over-the-counter topical antibiotic ointment containing a combination of three antibiotics: bacitracin zinc, neomycin sulfate, and polymyxin B sulfate. This triple-antibiotic formulation provides broad-spectrum coverage against common skin pathogens and is primarily used for the prevention and treatment of minor skin infections, cuts, scrapes, and burns.

Mechanism of Action

Neosporin's three components work synergistically to inhibit bacterial growth through distinct mechanisms:

• Neomycin sulfate: An aminoglycoside antibiotic that binds to the 30S ribosomal subunit, inhibiting bacterial protein synthesis
• Polymyxin B sulfate: A polypeptide antibiotic that disrupts bacterial cell membrane permeability by binding to phospholipids
• Bacitracin zinc: A polypeptide antibiotic that inhibits bacterial cell wall synthesis by interfering with dephosphorylation of the lipid carrier molecule that transports peptidoglycan precursors

This combination provides coverage against both Gram-positive and Gram-negative bacteria, including Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli, and Pseudomonas aeruginosa.

Indications

• Prevention of infection in minor cuts, scrapes, and burns
• Treatment of superficial bacterial skin infections
• Topical prophylaxis following minor surgical procedures
• Adjunctive therapy in wound care management

Dosage and Administration

• Application: Apply a thin layer to affected area 1-3 times daily
• Coverage: May be covered with a sterile bandage or left uncovered
• Duration: Use until healing is complete or for up to 7 days
• Special populations: No dosage adjustment required for renal or hepatic impairment
• Pediatric use: Generally safe for children over 2 years; consult physician for younger children

Pharmacokinetics

• Absorption: Minimal systemic absorption when applied to intact skin; increased absorption may occur through broken skin or large surface areas
• Distribution: Primarily local tissue distribution with negligible systemic distribution
• Metabolism: Not metabolized systemically
• Elimination: Primarily eliminated through desquamation of skin cells; negligible renal elimination

Contraindications

• Hypersensitivity to any component of the formulation
• Known hypersensitivity to other aminoglycosides
• Deep or puncture wounds
• Animal bites
• Serious burns
• Extensive areas of skin loss

Warnings and Precautions

• Allergic reactions: Contact dermatitis may occur, especially with neomycin component
• Superinfection: Prolonged use may result in fungal or bacterial superinfection
• Systemic absorption: Possible with application to large areas, broken skin, or under occlusive dressings
• Ototoxicity and nephrotoxicity: Theoretical risk with extensive application due to neomycin absorption
• Cross-hypersensitivity: Possible with other aminoglycosides
• Pregnancy: Category C - use only if clearly needed
• Breastfeeding: Exercise caution; unknown if excreted in human milk

Drug Interactions

• Neuromuscular blocking agents: Neomycin may potentiate neuromuscular blockade
• Other topical products: Concurrent use may cause physical or chemical interactions
• Systemic aminoglycosides: Increased risk of toxicity with concomitant systemic aminoglycoside therapy

Adverse Effects

• Localized itching
• Redness
• Skin rash
• Contact dermatitis

• Allergic reactions (urticaria, angioedema)
• Skin irritation
• Burning sensation
• Superinfection with nonsusceptible organisms

• Anaphylaxis (with extensive application to broken skin)
• Ototoxicity (with massive application)
• Nephrotoxicity (with massive application)

Monitoring Parameters

• Wound healing progress: Monitor for signs of improvement or worsening infection
• Local reactions: Assess for signs of contact dermatitis or allergic reactions
• Signs of superinfection: Monitor for emergence of fungal or resistant bacterial infections
• Systemic symptoms: With extensive application, monitor for ototoxicity (hearing loss, tinnitus) or nephrotoxicity

Patient Education

• Use only for minor skin injuries and infections
• Clean wound thoroughly before application
• Apply a thin layer; excessive use does not improve efficacy
• Discontinue use and consult healthcare provider if:

- Condition worsens or doesn't improve within 7 days - Rash, itching, or irritation develops - Signs of infection appear (redness, swelling, pus) - Symptoms suggest systemic reaction

• Do not use in eyes, ears, or deep wounds
• Keep out of reach of children
• Store at room temperature away from moisture

References

1. FDA OTC Monograph for First Aid Antibiotic Drugs. Federal Register 2020 2. Draelos ZD. The advantage of triple antibiotic ointment. J Am Acad Dermatol. 2008;58(1):166-168 3. Smack DP, Harrington AC, Dunn C, et al. Infection and allergy incidence in ambulatory surgery patients using white petrolatum vs bacitracin ointment. JAMA. 1996;276(12):972-977 4. Gehrig KA, Warshaw EM. Allergic contact dermatitis to topical antibiotics: Epidemiology, responsible allergens, and management. J Am Acad Dermatol. 2008;58(1):1-21 5. Trookman NS, Rizer RL, Ford R, et al. Immediate and long-term clinical benefits of a topical treatment for prescription and nonprescription acne. J Clin Aesthet Dermatol. 2009;2(11):26-31 6. Neosporin® [package insert]. Johnson & Johnson Consumer Inc. 2021 7. Eady EA, Cove JH. Topical antibiotic therapy: current status and future prospects. Drugs Exp Clin Res. 1990;16(8):423-433