Antiseptics and Disinfectants


  • Sterlization

  • Freeing of an article, surface or medium by removing or killing all micro-organisms including vegetative form of bacteria, spores, viruses, fungii

  • Disinfection

  • Destruction or inhibition of growth of all pathogenic organisms (bacteria, viruses, fungii) on non living surfaces

  • If spores are also killed process is Sterlization

  • Antiseptics

  • These are chemical substances which inhibit the growth or kill micro-organisms on  living surfaces such as skin & mucous membrane.

Properties of good antiseptic/ disinfectant


2.Non  staining &  good odour

3.Active against all pathogens

4.Active in presence of pus, blood & exudates

5.Rapid acting

6.Non irritating to tissues / non corrosive

7.Non absorbable

8.Non sensitizing/

  • Mechanisms of action of antiseptic and disinfectants

  • Oxidation of bacterial protoplasm

–Potassium permagnate, H202, Halogens

  • Co-agulation (denaturation) of bacterial proteins & disrupt cell membrane

–Phenols, chlorhexidine, alcohols, aldehydes

  • Detergent like action ↑ permeability of bacterial cell membrane

–Cetrimide, soaps

  • Classification

  • Phenol derivatives:

–phenol, cresol, hexachlorophene, chlorohexylenol (dettol)

  • Oxidizing agents:

–Hydrogen peroxide.

  • Halogens:

–Iodine,  chlorine,  chlorophores.

  • Biguanides:


  • Quaternary ammonium:


  • Phenol

  • Earliest used, reference standard

  • Protoplasmic poison,

–injures tissues & cells at high conc causes skin burn

  • MOA:

–denaturating bacterial protiens.

  • USES :

–To disinfect urine, faeces, pus, burns.

  • Extremely irritating, corrosive

  • CRESOL (Lysol)

  • Methyl Derivative of phenol, less damaging to tissues than phenol.

  • 3-10 times more active

  • used for disinfection of utensils, excreta & for washing hands.

  • Chloroxylenol (Dettol)

  • Phenol derivative

  • Does not co-agulate proteins,

  • Non corrosive,Non irritating to skin

  • Commercial 4.8 % solution used for surgical antisepsis

  • Skin cream and soap: 0.8%

  • Mouth wash 1%

  • Hexachlorophene

  • Commonly incorporated in soap

  • Effectively only against Gm+ve

  • Slow but persistant action

  • >2% preparations banned

  • Oxidizing agents

  • Potassium permagnate:

– Purple crystals, highly water soluble, liberates oxygen which oxidizes bacterial protoplasm.

–Used for gargling, irrigating wounds, urethra (condy`s lotion diluted solution of 1:4000  to 1:10,000 )

–High conc cause burns

–It is also used to disinfect water in ponds.

–Stomach wash in alkaloidal poisoning

  • Oxidizing agents

Hydrogen Peroxide

–liberates nascent  oxygen which oxidizes necrotic matter & bacteria.

–Helps in loosening  &  removing  slough,  ear wax etc.

Benzoyl Peroxide

–Widely used drug for acne.

–liberates O2 in presence of water which kills bacteria, specially anaerobes

  • Halogens

  • Iodine,

  • Iodophores,

  • Chlorine,

  • Chlorophores

  • Iodine

  • Rapidly acting broad spectrum (bacteria, fungi,virus)

  • Acts by iodinating and oxidizing microbial protoplasm.

  • Used for cuts, degerming skin before surgery.

  • Adverse effect: cause burns & blisters

  • Iodophores

  • Known as povidine iodine.

  • Non toxic, non staining prolonged action.

  • Used on boils, furunculosis, burns, ulcers, tinea, surgical srub, disinfecting surgical instruments, non specific vaginitis.

  • Chlorine

  • potent germicide. Kills pathogens in 30 sec. used to disinfect urban water supplies.

  • 0.1 to 0.25 ppm

  • Cholorophores

(1)  Chlorinated lime (bleaching powder)

–obtained by action of chlorine on lime.

–used to disinfect drinking water

(2)  Sodium hypochlorite

– Powerful  disinfectant used in dairies for milk  cans.

–Too Irritant to be used as antiseptic.

–Root canal therapy in dentisry

  • Biguanides

Chlorhexidine: (Savlon)

– Acts by disrupting bacterial cell membrane & denaturation of bacterial proteins

– Non irritant ,more active against gram +ve     bacteria.

–Used in for surgical scrub, neonatal bath, mouth wash &  general skin antiseptic.

–Most widely used antiseptic in dentisry 0.12-0.2% oral rinse or 0.5 -1 % tooth paste

  • Quarternary ammonium antiseptics cetrimide

  • Detergents: Cidal to bacteria, fungi & viruses.

  • Act by altering permeability of cell membrane

  • Efficiently remove dirt and grease

  • Widely used as antiseptics & disinfectants for surgical   instruments, gloves etc

  • Combined with chlorhexidine (savlon)

  • Soaps

  • Anionic detergents

  • Weak antiseptics with cleansing action

  • Washing with soap and warm water one of the most effective methods of preventing disease transmission

  • Affect only Gm+ bacteria

  • Alcohols

  • Ethanol

–Antiseptic, cleansing agent at 40-90% conc.

–Act by precipating bacterial proteins

– Irritant, should not be applied on mucous membrane, ulcers, open wounds.

  • Aldehydes (Formaldehyde)

  • Used for fumigation.

  • 37 % aqueous solution called as formalin.

  • Protoplasmic poison , denaturates protiens.

  • Used for preserving dead tissues.

  • Use as antiseptic  restricted due to bad odour & irritation

  • Glutaraldehyde is a better sterlizing agent

  • Acids

Boric acid

  • weak antiseptic , bacteriostatic.

  • used for mouth wash, irrigation eyes, glossitis.

  • Adverse effect: vomiting ,abdominal pain on systemic absorption.

  • Metallic salts


  • Silver sulphadiazine is active against pseudomonas seen in burns patient.

  • Silver nitrate highly active against gonococci


  • Mild antiseptic, used as eye wash, ear drops.

  • Dyes

Gentian violet:

– Active against bacteria (gram + ve), fungi

–Used on chronic ulcers, furunculosis, bed sores, ring worms.


–Active against  gram +ve bacteria & gonocci

–suitable for chronic ulcers & wounds

–Do not retard healing, non irritant

  • Ectoparasiticides

  • These are drugs used to kill parasites that live on body surfaces

lice → cause pediculosis (hair infection)

mites → cause scabies(skin infection)

  • Drugs used are







  • Permethrin

  • Broad spectrum causes neurological paralysis in insects.

  • 100 % cure rate nearly

  • Single application needed in most  cases.

  • Few patients experience itching ,burning.

  • first drug of choice for scabies & pediculosis.

Scabies: apply  all over the body except face & head . Wash  after 8- 12 hrs.

Head louse: massage about 30 g in to scalp  and wash  after  10 min.

  • Lindane

  • Broad spectrum insecticide which kills lice and mites by penetrating their chitinous cover

  • Properties similar to permethrin.

  • Cure rate low & resistance seen.

  • Disadvantage: being lipid soluble CNS toxicity like vertigo , convulsions seen.

  • Application similar to permithrin.

  • combination with benzyl benzoate is more effective.

  • Benzyl benzoate

  • Oily liquid with aromatic smell.

  • Cure rate 76 – 100% ; second application required after 24 hrs.

  • Toxicity is low. Application similar to permethrin.

  • Use has declined due to skin irritation.

  • Contra indicated in children because of neurological symptoms & skin irritation.

  • combination with lindane highly effective.

  • Crotamiton

  • low cure rates

  • Better results if applied for 5 days in children

  • Less irritation and toxicity

  • May be preferred in children as second choice

  • Ivermectin

  • Anti helminthic drug which has been recently found effective against scabies & pediculosis.

  • A single 0.2 mg /kg ( 12mg in adults) has 91- 100 %  cure rate.

  • Contra indicated in children < 5yrs , preganant & lactating women.

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