7.4 Topical Agents: Antiseptics, Antibiotics & Active Topicals
Key Takeaways
- Antiseptics (povidone-iodine, cadexomer iodine, chlorhexidine, hypochlorous acid and sodium hypochlorite, polyhexanide (PHMB), octenidine, silver, medical-grade honey, and acetic acid) act on many organisms at once and rarely select resistance, so they are preferred over topical antibiotics for bioburden control.
- Topical antibiotics such as neomycin, bacitracin, and mupirocin should be used sparingly on chronic wounds because they promote resistance and commonly cause allergic contact dermatitis; neomycin and bacitracin are frequent allergens.
- Use antiseptics for a defined period (for example, a 2-week trial) with a clear goal, then reassess; stop or switch when the wound improves or if it fails to respond.
- Hydrogen peroxide should not be instilled under pressure or packed into closed cavities or sinus tracts because of the risk of gas embolism, and it offers little benefit in chronic wounds.
- Becaplermin 0.01% gel (recombinant PDGF-BB) is FDA-approved for neuropathic diabetic foot ulcers that extend into subcutaneous tissue or beyond and have adequate blood supply, used with good wound care including offloading; its boxed cancer warning was removed in 2018.
7.4 Topical Agents: Antiseptics, Antibiotics & Active Topicals
Core Clinical Principle: Topical agents are prescriptions. Each needs an indication, a goal, a time limit, and a plan for reassessment. Antiseptics reduce bioburden without driving much resistance, topical antibiotics have narrow roles, and active topicals such as growth factors and enzymes work only in a well-prepared wound.
The CWSP outline lists topical agents in Patient Management, and managing wounds with dressings and topical agents and prescribing systemic or topical antimicrobial therapy are listed tasks. Dressings that carry antimicrobials (such as silver and iodine dressings) are covered with dressing selection; this section focuses on the agents themselves.
Wound Cleansing
- Solutions: Normal saline or potable tap water is suitable for most wounds; trials and systematic reviews have not shown more infections with drinkable tap water. Use an antiseptic cleanser when bioburden or biofilm is suspected.
- Irrigation pressure: About 4 to 15 psi removes debris without driving bacteria into tissue; a 35-mL syringe with a 19-gauge angiocatheter delivers about 8 psi.
- Temperature: Warm solutions reduce pain and avoid cooling the wound bed.
Antiseptics
| Agent | Common Forms | Strengths | Cautions |
|---|---|---|---|
| Povidone-iodine | 10% solution, ointment | Broad spectrum, inexpensive; dries stable eschar | Stings; avoid large-area or long-term use in thyroid disease, pregnancy, and infants |
| Cadexomer iodine | 0.9% gel, paste, or pad | Slow iodine release; absorbs exudate; evidence of biofilm activity | Maximum amounts per application and course; avoid in iodine sensitivity, thyroid disease, pregnancy, and young children |
| Chlorhexidine | 0.05% cleanser; 2–4% skin preparations | Broad spectrum, residual activity | Rare anaphylaxis; avoid contact with eyes, middle ear, and meninges; caution in premature infants |
| Sodium hypochlorite (Dakin's solution) | 0.5% (full), 0.25% (half), 0.125% (quarter), and more dilute | Broad spectrum, deodorizing, dissolves necrotic tissue | Cytotoxic at higher strengths; protect periwound skin; short courses |
| Hypochlorous acid | Dilute solutions and gels (commonly well below 0.1%) | Broad activity with low tissue toxicity at use concentrations | Short shelf life once opened for some products |
| Polyhexanide (PHMB) | 0.1% solution or gel, often with betaine surfactant | Low cytotoxicity, good for cleansing and soaks, biofilm disruption | Rare allergy; avoid cartilage and central nervous system contact |
| Octenidine | 0.05–0.1% solutions and gels | Broad spectrum, low toxicity | Tissue damage reported when injected under pressure into closed spaces |
| Silver | Ionic silver, nanocrystalline silver, silver sulfadiazine | Broad spectrum, many dressing forms | Staining; rare argyria; use for defined periods |
| Medical-grade honey | Leptospermum (manuka) gels and dressings | Osmotic effect, low pH, hydrogen peroxide activity, methylglyoxal; supports autolysis | Stinging; monitor glucose in large wounds; use sterilized medical-grade products only |
| Acetic acid | 0.25–1% soaks (up to 5% in some protocols) | Lowers pH; active against Pseudomonas aeruginosa | Stings; cytotoxic at high strength |
Hydrogen peroxide (3%) releases oxygen that foams away debris, but it is cytotoxic, adds little in chronic wounds, and should never be packed into or forcefully irrigated into deep cavities or sinus tracts, where released gas can cause gas embolism.
Antiseptic Stewardship
International consensus favors using an antiseptic for about 2 weeks as a trial when local infection or biofilm is suspected, alongside debridement, then reassessing: continue while signs improve, stop when they resolve, and change the plan if there is no improvement. In-vitro cytotoxicity does not always predict clinical harm, but the lowest effective concentration for the shortest useful time is a sound rule.
Topical Antibiotics
| Agent | Role | Problems |
|---|---|---|
| Mupirocin | Nasal MRSA decolonization; impetigo | Resistance develops with prolonged use |
| Bacitracin, neomycin, polymyxin B | Minor acute wounds | Neomycin and bacitracin are common contact allergens, especially in patients with stasis dermatitis and leg ulcers |
| Metronidazole gel (0.75–1%) | Odor from anaerobes in malignant and palliative wounds | Limited role in healing |
| Silver sulfadiazine | Burns | Delays epithelialization; avoid in late pregnancy and newborns |
| Gentamicin cream | Rarely justified | Promotes resistance to an important systemic drug |
Guidelines such as those from the IWGDF advise against using topical antimicrobials to try to speed healing of uninfected diabetic foot ulcers, and systemic antibiotics, not topical ones, treat spreading infection.
Active Topicals and Skin Protectants
- Becaplermin 0.01% gel: Recombinant human platelet-derived growth factor-BB for lower-extremity neuropathic diabetic ulcers that extend into subcutaneous tissue or beyond with adequate blood supply, applied daily with debridement and offloading. It should not be used on wounds with neoplasm at the site. The boxed warning about cancer mortality was removed in 2018.
- Collagenase (250 units/g ointment): Enzymatic debridement; keep away from agents that inactivate it (such as silver and iodine products and detergents).
- Topical timolol: Beta-blocker used off-label for chronic wounds and pyogenic granuloma; small studies suggest faster epithelialization.
- Topical corticosteroids: Potent steroids (such as clobetasol) for pyoderma gangrenosum edges, hypergranulation, and periwound dermatitis; tacrolimus is a steroid-sparing option.
- Silver nitrate sticks: Chemical cautery for hypergranulation and pinpoint bleeding; causes pain and black staining.
- Skin protectants: Zinc oxide, dimethicone, and petrolatum creams and ointments, and no-sting liquid barrier films (terpolymer or cyanoacrylate), protect periwound skin from exudate, adhesives, and incontinence.
- Topical oxygen: Devices that deliver oxygen to the wound surface have some supportive trials, but Medicare's hyperbaric oxygen national coverage determination states that topical oxygen application is not covered.
Clinical Traps
Trap 1: Endless Silver or Iodine
Months of antimicrobial dressings on a wound that is not improving delay the real answer: debridement, offloading, revascularization, biopsy, or a systemic infection workup.
Trap 2: Spreading Dermatitis Blamed on Infection
An itchy, weeping, sharply shaped rash that spreads beyond the area where an ointment was applied suggests allergic contact dermatitis. Stop the agent rather than adding antibiotics.
A 67-year-old man has a diabetic foot ulcer with a 4-cm plantar sinus tract that drains foul-smelling fluid. A home health nurse asks whether to flush the tract with 3% hydrogen peroxide using a syringe. What is the best response?
A 74-year-old woman with a venous leg ulcer has used an over-the-counter triple antibiotic ointment (neomycin, bacitracin, and polymyxin B) for 3 weeks. She now has an intensely itchy, weeping, erythematous eruption with sharp borders that extends several centimeters beyond the ulcer onto skin where the ointment was spread. She is afebrile and the ulcer bed is unchanged. What is the most likely diagnosis and best management?
A 62-year-old man with type 2 diabetes has a 3-month-old neuropathic plantar ulcer that extends into subcutaneous tissue. His toe pressure is 70 mmHg, the ulcer has been sharply debrided, infection has been excluded, and he is adherent to a removable walker. His clinician is considering becaplermin gel. Which statement about becaplermin is accurate?