Antiseptics Disinfectants

Antiseptics and Disinfectants

Antiseptics are antimicrobial agents to apply on the living surface to kill or prevent the growth of microorganism to reduce or prevent microbial infection or sepsis. Disinfectants are antimicrobial agents to apply on the nonliving surface (inanimate surface) to kill or prevent microorganism growth to reduce their number to prevent infection. They do not kill spores. Antibiotics are the metabolic product of bacteria that kill or prevent the growth of the selective microorganism. Antibiotics are usually used to control systemic microorganism infections. Antiseptics are not used for systemic microorganism infections. They are used for topical infections. They are not selective and harm almost all microorganisms. They are used to clean the wound and do not support wound healing. In fact, they impair wound healing.

Word germicide includes both antiseptic and disinfectant. They are widely used with household products soap, toothpaste, after saving lotion etc.

Mechanism of action: Antiseptics and disinfectants produce their action by any one or combination of following mechanisms:

·         Microorganism protoplasm oxidation

·         Microorganism protein denaturation

·         Microorganism cell metabolism impairment

·         Surfactant like action

Ideal antiseptic and disinfectant: Ideal antiseptics and disinfectants should of following characteristics:

·         It should not be absorbed from skin or mucous membrane into systemic circulation

·         It should be chemically stable

·         It should have a broad antimicrobial spectrum

·         It should have rapid action

·         It should be nonirritating to tissues

·         It should not impair wound healing

·         It should be effective even in presence of pus, exudates, and tissue degradation products

·         It should not have an offensive odor, color and staining properties.

·         It should not produce hypersensitivity reaction

Classification

·         Acids: Ethanol, Isopropyl Alcohol

·         Aldehydes: Formaldehyde, Glutaraldehyde,

·         Phenol Derivatives: Phenol, Cresol, Paraben, Thymol, Resorcinol, Chlorhexidine, Chlorhexidine Gluconate, Chloroxylenol, Hexachlorophene

·          Halogens: Chlorine, Iodine, Iodophores, Chloramine

·         Oxidising Agents: Hydrogen peroxide, Potassium permanganate, Benzoyl peroxide

·         Dyes: Gentian Violet, Methylene Blue, Brilliant Green

·         Heavy Metals: Mercury Compounds, Silver Compounds, Zinc Compounds

ACIDS: Acids are bactericidal at pH less than 3 and bacteriostatic at pH between 3 and 6. They are used as antiseptic, fungicide and to preserve food.

·         Acetic Acid: 5% concentration of acetic acid is used as bacteriostatic. Less than 5% concentration acts as bacteriostatic. 1% acetic acid solution is used in surgical dressings as antimicrobial agents. 0.25% to 2% acetic acid solution is used as an antimicrobial agent in external ear infection and lower urinary tract infection as an irrigation solution. It is very effective against aerobic gram –ve bacteria. 5% acetic acid solution is used to suppress the growth of microorganism on the extensively burning skin.

·         Benzoic Acid: 0.1% benzoic acid prevents the growth of bacteria and fungus in acidic media. It is tasteless and nontoxic. Thus it is also used as a preservative.

·         Boric Acid: Aqueous solution of boric acid is used to irrigate eye, vagina, large wound, and bladder. It is less volatile than acetic acid, thus, it remains on the surface for longer duration upon topical application. 16.7% boric acid combine with salicylic acid is used to remove worts.

·         Salicylic acid: It is bacteriostatic, fungicidal and keratolytic. It is for external use to treat chronic leg ulcer, eczema, psoriasis, and seborrheic dermatitis. It is an ingredient of Whitefield’s ointment that contains benzoic acid and salicylic acid to treat tinea pedis infection.

ALCOHOL

·         Ethyl alcohol (Ethanol): It is an antimicrobial agent with low potency and moderate efficacy. Ethanol 60% v/v to 90%v/v is used as antiseptic. Its antiseptic property decreases above 80% v/v strength. It acts as bacteriostatic by denaturing bacterial proteins. Alcohol is an antimicrobial agent that has following properties:

o   Bacteriostatic and fungicidal

o   Ethanol 40% to 60% is most effective against staphylococci

o   Ethanol 70% control 90% of bacteria within 2c minutes on moist skin

o   Ethanol 80% or above has low antiseptic property

o   Ethanol increases the germicidal effect of chlorhexidine, iodine, iodophors, and hexachlorophene

o   Ethanol alone has not much effect on an open wound. It forms coagulum on an open wound. Bacteria may grow below coagulum

o   Ethanol produces irritation and burning on an open wound.

o   Ethanol is not much effective against spores

o   It is inflammable. Thus lesser surgery should be applied after complete evaporation of ethanol

o   Isopropyl Alcohol: It is more potent and less toxic than ethanol. 68% to 72% of isopropyl alcohol is used as a skin antiseptic.

ALDEHYDE: Aldehydes are effective against bacteria, spores, fungi, and viruses. Mainly formaldehyde and glutaraldehyde are used as a disinfectant.

·         Formaldehyde: 2% to 8% aqueous solution of formaldehyde is used as a germicide. It is used to disinfect inanimate (non-living) objects like surgical instruments. It should not be used as antiseptic to the mucous membrane. However, methenamine is urinary antiseptic that produces an antimicrobial effect in urinary tract by releasing formaldehyde in the urinary tract.

Formaldehyde solution polymerizes to form a white deposit in concentrated stock solution 

·         Glutaraldehyde: It polymerizes slowly than formaldehyde. 2%w/v solution is used as a broad-spectrum disinfectant. It is effective in alkaline pH not in acidic pH.

Formaldehyde and glutaraldehyde vapor are carcinogenic. They irritate the eye and mucous membrane of the respiratory tract. Both cause dermatitis. They are used to clean, disinfect, and sterilize heat-sensitive surgical instruments. They are also used to maintain an aseptic condition in the aseptic room, injectable manufacturing room etc by fumigation. They are used to disinfect incubators, cold rooms, benches,

· Chlorhexidine: It is most commonly used a surgical antiseptic. It is colorless, odorless with bitter and unpleasant taste. It is effective against bacteria but bacterial spores and acid-fast bacteria are resistant to chlorhexidine. It has a longer duration of action with higher therapeutic index. It is effective in presence of blood, pus, and soap. It is most effectve at pH 5.5 and 8

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