Solution Antiseptics: Savlon, Betadine, EUSOL, and H₂O₂

1. SAVLON (Chlorhexidine + Cetrimide)

• Cetrimide (cetavlon) - a quaternary ammonium compound (QAC)
• Chlorhexidine (hibitane) - a bisbiguanide compound

Mechanism of Action

• Carries a positive charge that binds to negatively charged bacterial cell membranes
• Disrupts cell membrane integrity, causing leakage of intracellular contents (potassium ions, nucleic acids, cytoplasmic enzymes)
• At higher concentrations, causes complete cell lysis

• Disrupts cytoplasmic membranes of both Gram-positive and Gram-negative bacteria
• At low concentrations: bacteriostatic - causes leakage of small molecules (K⁺)
• At high concentrations: bactericidal - causes complete cytoplasmic precipitation and coagulation
• Has an almost instant onset of action and sustained residual activity for many hours after application
• Shows an additive (cumulative) effect with repeated applications

Uses

• Wound cleaning and irrigation (aqueous Savlon used to wash out contaminated wounds)
• Pre-operative skin preparation and surgical scrubbing
• Disinfection of plastic appliances and instruments (normal strength, 20 minutes contact)
• Savlon 1 in 6 in spirit is effective for instrument soaking
• Disinfection of the autopsy room and surgical environments
• Burns dressings (chlorhexidine 1% creams and lotions)
• Hand lotions (0.5% alcoholic or aqueous chlorhexidine solutions)

Antimicrobial Spectrum

• Highly active against Gram-positive organisms
• Moderately active against Gram-negative organisms
• Some antiviral activity
• Limited activity against fungi and mycobacteria
• Inactivated by soaps and detergents

Advantages

• Rapid, almost instant onset of action
• Prolonged residual activity lasting hours post-application
• Cumulative/additive effect with repeated use
• Superior skin decontamination with lower postoperative infection rates compared to povidone-iodine
• Non-irritant to intact skin at standard concentrations
• Combined detergent + antiseptic effect (cetrimide cleans, chlorhexidine kills)

Adverse Effects

• Keratitis and corneal ulceration if direct contact with the cornea occurs - limits use near eyes
• Cochlear and vestibular toxicity if chlorhexidine reaches the inner ear through a perforated tympanic membrane - limits use near ears
• Tissue toxicity with prolonged exposure
• In vitro studies show chlorhexidine gluconate is toxic to fibroblasts and keratinocytes; when diluted to reduce cytotoxicity, it loses its anti-staphylococcal efficacy
• Inactivated by organic matter and anionic soaps/detergents

2. BETADINE (Povidone-Iodine)

Mechanism of Action

• The carrier slowly releases free iodine, which is the active germicidal agent
• Free iodine oxidizes microbial cell membranes and disrupts key molecular targets
• Iodine penetrates microbial cell walls and attacks amino acids (particularly thiol groups in cysteine and methionine), nucleotides, and fatty acid double bonds
• Net effect: irreversible oxidative damage to proteins, membranes, and nucleic acids
• Onset of action is within 1-3 minutes; activity persists for hours, though contact with blood or serum attenuates activity significantly

Uses

• Pre-operative skin preparation (applied undiluted around but not inside wounds)
• Contaminated traumatic wound cleaning (diluted to <1% for use inside wounds)
• Disinfection of blood culture bottles and medical equipment
• Surgical hand scrubbing (Betadine scrub 7.5%)
• Skin antisepsis for minor procedures (injections, cannulation)
• Combination skin preparation with alcohol (DuraPrep = iodine povacrylex + isopropyl alcohol)

Antimicrobial Spectrum

• Broad spectrum - active against Gram-positive and Gram-negative bacteria, fungi, mycobacteria, and viruses (virucidal)
• At 10% stock solution: strongly bactericidal and virucidal
• Does not stain the skin (advantage over aqueous iodine solutions like Lugol's)
• Non-irritant compared to aqueous iodine

Advantages (Iodophors over plain iodine)

• Non-irritant to skin - does not cause the burning and staining of aqueous iodine
• Does not stain skin or clothing
• Broad antimicrobial spectrum including viruses
• Slow release of iodine prevents sudden high-concentration toxicity
• Stable shelf life
• Available in multiple formulations (solution, scrub, ointment, gel)

Adverse Effects

• Undiluted solution is potentially toxic to wound tissue - should not be placed inside open wounds at full strength
• The detergent component in Betadine scrub (7.5%) is additionally toxic to wound tissue
• Painful/irritating in open wounds
• Iodine allergy - can cause allergic contact dermatitis; anaphylaxis is rare but documented
• Absorbed systemically through large wounds - can cause iodine toxicity (thyroid dysfunction)
• Activity is markedly reduced on contact with blood, serum, or pus (organic matter)
• Potentially teratogenic with repeated use
• Risk of tissue necrosis in wounds with prolonged exposure to significant volumes

3. EUSOL (Edinburgh University Solution of Lime)

• Chlorinated lime (bleaching powder) 1.25 g
• Boric acid 1.25 g
• Water to 100 mL
• pH: slightly acidic (~7.5-8)
• Active ingredient: hypochlorous acid (HOCl), which is also the active species in Dakin's solution (sodium hypochlorite 0.5%)

Mechanism of Action

• On contact with wound fluids, releases hypochlorous acid (HOCl)
• HOCl is a powerful oxidizing agent: it oxidizes and chlorinates proteins in the bacterial cell wall and cytoplasm
• Disrupts thiol (-SH) groups of bacterial enzymes, causing irreversible inactivation
• Also acts as a proteolytic/debridement agent - the alkaline pH and oxidizing action break down necrotic tissue and liquefy slough (hence its historical use in debridement)
• Activity is short-lived as the solution is unstable and rapidly inactivated by organic matter

Uses

• Wound debridement and sloughing - historically used to clean dirty, sloughing wounds and liquefy necrotic tissue
• Infected, sloughing, necrotic wounds where mechanical debridement is needed
• Wet dressings for infected wounds
• Historically used in World War I wound management (Carrel-Dakin irrigation)
• Occasionally still used in infected pressure ulcers and burns where debridement is required

Advantages

• Effective at liquefying and removing necrotic tissue/slough (combined antiseptic + debridement)
• Cheap and easy to prepare
• Active against a wide range of bacteria including anaerobes
• Useful where mechanical debridement is not possible

Adverse Effects

• Cytotoxic to granulation tissue, fibroblasts, and keratinocytes - damages healthy healing tissue
• Delays wound healing - repeated use impairs formation of granulation tissue
• Causes pain and irritation in wounds
• Very unstable - short shelf life, must be freshly prepared; loses activity rapidly
• Inactivated quickly by organic matter (pus, blood, exudate)
• Cannot be used on clean granulating wounds (destroys new epithelium)
• Not recommended for routine wound care in modern practice due to evidence of impaired healing

Note: EUSOL has largely fallen out of favor in modern wound management. Current evidence supports that its tissue-toxic effects outweigh its antiseptic benefits in healing wounds. It may still have a limited role in necrotic, sloughy wounds requiring debridement.

4. HYDROGEN PEROXIDE (H₂O₂)

• 3% (10 vol) - standard wound care / antiseptic use
• 6% (20 vol) - bleaching / stronger antiseptic
• 30% (100 vol) - industrial; dangerous

Mechanism of Action

• H₂O₂ acts as an oxidizing agent
• In contact with wound tissues, the enzyme catalase (present in tissue and blood) rapidly decomposes H₂O₂:

  2H₂O₂ → 2H₂O + O₂ (gas)

• The vigorous release of nascent oxygen creates a mechanical effervescent/bubbling action
• This oxygen bubbling physically dislodges debris, necrotic tissue, clots, and bacteria from wound surfaces (mechanical cleansing)
• The oxidizing environment also has direct, brief bactericidal effect by oxidizing microbial thiol groups and cellular components
• However, it is classified as a very weak antibacterial agent - its antimicrobial effect is transient and mainly from the short-lived oxidizing burst

Uses

• Cleaning blood-encrusted wounds and removing blood-soaked adherent dressings (primary current use)
• Removing coagulum from wound surfaces where mechanical débridement is needed
• Oral antiseptic (diluted): mouthwashes for gingivitis and aphthous ulcers
• Ear canal irrigation to soften and remove earwax
• ENT: irrigation of wounds with Savlon + hydrogen peroxide + sterile water (mechanical washing effect is the important mechanism here)
• Penile implant salvage washout protocols use H₂O₂ among a series of antiseptic solutions
• Historically used as a general wound antiseptic (now largely replaced)

Advantages

• Cheap and widely available
• Effective at mechanically dislodging debris through effervescence
• Useful for cleaning blood-encrusted or dried dressings
• Some short-lived bactericidal activity
• Good for oral and ENT applications at low concentrations

Adverse Effects

• Hemolytic - lysates red blood cells (not to be used in closed cavities or blood-rich wounds)
• Toxic to granulation tissue - oxygen bubbles physically lift newly formed epithelium off the wound surface, damaging it
• No significant antiseptic properties when used for sterile skin preparation (Andrews' Diseases of the Skin confirms this)
• Cytotoxic to fibroblasts at standard concentrations
• Should NOT be used in closed or blind-ended wound cavities - risk of oxygen gas embolism (rare but fatal)
• Should NOT be used on clean granulating wounds - destroys epithelial regeneration
• Provides only transient bactericidal effect - not sustained
• High concentrations (>3%) cause tissue burns and whitening

Summary Comparison Table

• Park's Textbook of Preventive and Social Medicine - antiseptics classification
• Fitzpatrick's Dermatology - topical antiseptic MOA
• Roberts and Hedges' Clinical Procedures in Emergency Medicine - antiseptic wound care table
• 22nd Edition Pye's Surgical Handicraft - Savlon wound management
• Andrews' Diseases of the Skin - H₂O₂ in surgical antisepsis
• Dermatology 2-Volume Set 5e - wound infection antiseptic management

Savlon - Concentrations of All Preparations

Standard Product Formulations

Dilution Guidelines for Use

Chlorhexidine-Cetrimide Irrigation Solutions (Baxter / clinical grade)

Important warning: Savlon should never be used undiluted on skin - documented cases of chemical burns (including scrotal burns in paediatric circumcision cases) have been reported from undiluted application.

Betadine (Povidone-Iodine) - All Preparations and Concentrations

All Available Formulations

Diluted Wound Use Concentrations

Key clinical principle: The 10% undiluted solution is too concentrated for use inside open wounds. Diluting to <1% PVP-I is safe and effective for contaminated wound interiors. Below 0.1%, the bactericidal effect becomes negligible.

Available Iodine Content Summary

• 10% PVP-I solution = 90% water + 8.5% povidone polymer + 1% available iodine (free iodine ~1 ppm in equilibrium)
• 7.5% scrub = 0.75% available iodine
• 2.5% spray = 0.25% available iodine
• The free iodine concentration (~1 ppm) at equilibrium is actually the germicidal species - paradoxically, more dilute solutions can release proportionally more free iodine initially