antiseptics & disinfectants

ANTISEPTICS & DISINFECTANTSDisinfection is destruction of all microbes but not their spores. If spores are also killed, then this is called sterilization.

Antiseptic is the killing of microbes and can be used on living tissues. The word germicide can be used for drugs either.

MECHANISM OF ACTION• Oxidation of bacterial protoplasm• De-naturation of bacterial proteins• Detergent like action• Competition with essential substrates for imp. enzymes in bacterial

cell.An ideal germicide should have wide antibacterial spectrum Chemically stable Rapid action Non irritating to tissues No interference with wound healing even in presence of pus,

exudates and tissue degradation products

CLASSIFICATION• Acids : boric acid, benzoic acid• Alcohols : ethanol, isopropyl alcohol• Aldehydes : formaldehyde, glutaraldehyde• Surfactants : Soaps, Cetrimide• Phenol derivatives : phenol, cresol• Halogens : iodine, chlorine• Oxidizing agents : Hydrogen peroxide, potassium

permanganate• Dyes: Gentian violet, brilliant green• Metallic salts : Silver nitrate, zinc compounds

ACIDS• Boric acid & benzoic acid have weak

bacteriostatic & fungistatic activity. Aqueous solution of boric acid are used for irrigating eyes, bladder, vagina & large wounds.

ALCOHOLSEthyl alcohol is used to clean the skin before

injections & surgeries. Isopropyl alcohol is more potent and more toxic than ethanol. It is used in 68-72% concentration as skin antiseptic

ALDEHYDES• FORMALDEHYDE: It is a gas at room temperature used

for fumigation, the 40% aqueous solution is noncorrosive and has a broad antimicrobial spectrum. It has a pungent odour & is highly irritant to respiratory mucosa & eyes.

Mechanism of action of formaldehyde : act by alkylation(transfer of an alkyl group from one molecule to another) of chemical groups in proteins & nucleic acid.

Uses : I. Used for fumigation & sterilization of instruments

which cannot be moistened with solutionII. 40% solution(100% formalin) in h20 is used for

disinfection of surgical instruments and gloves.

SURFACTANTS• Surfactants are chemicals that lower surface tension

of solution & are termed as detergents, They maybe anionic(-vely charged) cationic(+vely charged ion) ampholytic (type of amino acid that changes its charge depending on the pH of aqueous solution) or polysorbates (any of several emulsifiers used in the preparation of some pharmaceuticals and foods)

• Anionic surfactants : eg soaps• Cationic surfactanats: eg. Cetrimide

PHENOL DERIVATIVES• Phenol is one of the oldest antiseptics introduced by LORD LISTER

IN 1867. It is bactericidal & fungicidal but has poor action against spores & viruses. It acts by denaturing the bacterial proteins. It also has a mild anaesthetic effect. It is a protoplasmic poison. Protoplasmic poisons are substances that if a healthy living cell is exposed to in significant amounts, the cell will be adversely affected, damaged, or killed.

• Uses : A. Disinfection of urine, faeces, sputum of patientsB. Antipruritic effect because it is an anaesthetic • Cresol is methylphenol. It is used for disinfecting utensils &

excreta

HALOGENS

• It is a powerful bactericidal, sporicidal, fungicidal and viricidal agent.

• Disadvantages: Irritating, painful, stains the area and may delay wound healing

• Uses of iodine : I. As a tincture: used before surgeries to clean the

skinII. Mandl’s paint : treatment of tonsilitis & pharyngitisIII. Iodine ointment : in ringworm infections

IODIZING AGENTS• Hydrogen peroxide : It is a colourless and

odourless liquid. On application there is effervescence & helps in removing tissue debris, ear wax etc. Action of duration is short. It is also a deodrant

• Uses : cleansing wounds, abscesses & for irrigation

DYES

• Gentian violet : effective against gram positive organisms and fungi. Staining is the only disadvantage. It is non irritant and potent antiseptic. 0.5-1% solution is used topically on burns & boils, eczema(Eczema symptoms include itchy, red, and dry skin caused by inflammation)

• Brilliant green : action is similar to gentian violet.

Metals

• Zinc salts : have astringent & mild antiseptic properties. Zinc ointment is used as an ointment or lotion eczema, impetigo & psoriasis.

• Mercury compounds: act by inhibiting sulphydryl enzymes of bacteria. They are not commonly used.

BY – NIHARIKA BSc nursing 2nd year