Antiseptic and Disinfectant
- Antiseptic: It is an agent used to eliminate microorganisms on living tissues.
- Disinfectant: It is an agent used to eliminate microorganisms on inanimate objects.
Characteristics of ideal antiseptic and disinfectant
- It should be effective against all pathogens, like bacteria, viruses, fungi, protozoa, including spores.
- It should not delay wound healing.
- It should be effective in the presence of organic matter like blood, pus and excreta.
- It should be stable.
- It should not be toxic if absorbed or cause irritation on topical application.
- It should not corrode metals.
1. Phenols and related agents: Phenol, cresol, chlorhexidine, resorcinol, hexachlorophene, and chloroxylenol.
2. Alcohols: Ethyl alcohol and isopropyl alcohol.
3. Aldehydes: Formaldehyde and glutaraldehyde.
4. Oxidizing agents: Hydrogen peroxide and potassium permanganate.
5. Halogens and halogen-releasing agents: Chlorine, sodium hypochlorite, iodine, and iodophors
6. Acids: Benzoic acid and boric acid.
7. Metallic salts: Silver nitrate and zinc oxide.
8. Dyes: Gentian violet, brilliant green, and methylene blue.
9. Surface-active agents (detergents): Common soaps, cetrimide, benzalkonium chloride, and cetylpyridinium chloride.
10. Gases: Ethylene oxide and -propiolactone.
11. Miscellaneous: Nitrofurazone.
Phenols and related agents
They are protoplasmic poisons. They denature bacterial proteins and disrupt the cell wall. Their efficacy is reduced in the presence of organic matter.
1. Phenol (carbolic acid)
- Rarely used as antiseptic, as it is corrosive and can penetrate intact skin.
- Used to disinfect sputum, pus, excreta and discarded cultures.
- Accidental or suicidal ingestion can cause corrosion of gastrointestinal tract (GIT), convulsions, hypothermia and collapse.
2. Cresol (methylphenol)
- More active and safer than phenol.
- Used to disinfect utensils, excreta and infected glassware.
3. Lysol (soapy emulsion of cresol)
- Commonly used to disinfect the floor in hospitals and houses.
- As antiseptic to wash hands.
- Active ingredient of Dettol, less toxic than phenol.
- Used to disinfect surgical instruments and as an antiseptic for skin before any surgery.
- Nonstaining and less toxic.
- It has keratolytic and antipruritic properties; hence it is used in eczema, ringworm and seborrhoeic dermatitis.
- Chlorinated phenol.
- Greater than 2% solution is not used.
- Used as an antiseptic for skin before surgery, furunculosis and seborrhoeic dermatitis.
- Used as a mouthwash and as an antiseptic for skin prior to surgery.
- Chlorhexidine mouthwash enhances wound healing, if used before dental procedures. It is used as an antiplaque and anti-gingivitis agent.
- Taste alteration and staining of oral cavity are the common side effects.
They act by denaturing bacterial proteins and precipitating them.
1. Ethyl alcohol
- 70% ethyl alcohol is used as an antiseptic on skin before giving
- injections and surgical procedures.
- Its antiseptic efficacy decreases above 90%.
- Highly irritant open wounds, mucosa, ulcers and scrotum.
- It is not useful for disinfecting instruments, as it promotes rusting.
- 2. Isopropyl alcohol
- More potent, 68–72% is used as an antiseptic.
- Can be used to disinfect clinical thermometers.
They act by denaturing the proteins. They are protoplasmic poisons.
1. Formaldehyde (Formalin)
- Used for disinfection of sputum, removal of warts on palms and soles, to treat hyperhidrosis, and preservation of anatomical and pathological specimens.
- Formaldehyde gas is used for fumigation of wards and operation theatres, and rarely for sterilization of heat sensitive instruments and gloves.
- Preferred to formaldehyde to sterilize surgical instruments, plastic endotracheal tubes, face masks,
- Corrugated rubber tubes, endoscopes, respirators and thermometers, etc.
- 2% solution is used to treat hyperhidrosis of palms and soles.
They act by releasing nascent oxygen, which oxidizes the bacterial protoplasm.
1. Hydrogen peroxide
- Colorless liquid.
- Effervescence is seen when applied to tissues due to presence of enzyme catalase, which degrades hydrogen peroxide.
- Used for cleaning wounds and abscess cavities, removal of slough and ear wax.
- Can also be used to disinfect contact lenses, plastic implants and surgical prostheses.
2. Potassium permanganate
- Soluble in water.
- Condy lotion is 1:4000–1:10,000 solution of potassium permanganate, used for gargling.
- 5% solution is used as a styptic.
- 1% solution is used for fungal infections.
- Used topically for snake and scorpion bites, and for stomach wash in alkaloid poisoning.
- Concentrated solution can cause burns and blisters on topical application.
- Not used to disinfect surgical instruments, as it promotes rusting.
They are oxidizing agents.
It is used for the disinfection of water. Some of its preparations are:
- Chloramines: They act by releasing chlorine. They can be used as mouthwash and for dressing of wounds.
- Chlorinated lime (bleaching powder)
i. Acts by releasing chlorine.
ii. Used to disinfect drinking water and toilets.
iii. Disadvantage is that it is highly unstable and loses its activity on storage.
2. Sodium hypochlorite
Used as a root canal disinfectant.
It is cheaper, but it needs to be freshly prepared and has corrosive effects on metals.
- Has the property of oxidizing the protoplasm of microbes.
- Antiseptic efficacy decreases in the presence of organic matter.
- Hypersensitivity reactions can occur with iodine.
i. Tincture iodine (2% iodine in alcohol)
- Used as an antiseptic on skin for wounds and prior to surgery.
- Stains the skin.
ii. Mandl’s paint
- Contains iodine in potassium iodide and glycerine.
- Used topically in tonsillitis and pharyngitis.
iii. Lugol’s iodine
- Contains 5% iodine in 10% solution of potassium iodide.
- Used in thyrotoxicosis.
- Act by releasing iodine, e.g. povidone iodine.
- Non-irritant and does not stain the skin.
- Used in burns, boils, prior to surgery, disinfection of instruments and endoscopes.
- 1% solution can be used as a mouth rinse for gingivitis and before dental procedures.
Antiseptic activity is mainly due to their antibacterial activity.
1. Boric acid and sodium borate (Borax);
a. Fungistatic and bacteriostatic.
b. 2–4% solution is used as a mouthwash.
c. 30% paint for stomatitis and glossitis.
d. 10% ointment for cuts and abrasions.
e. Systemic absorption can cause abdominal pain, diarrhea, vomiting, visual disturbances and kidney damage.
2. Benzoic acid
Antibacterial and antifungal.
Whitfield’s ointment (6% benzoic acid + 3% salicylic acid) is used for ringworm infections.
1. Zinc sulphate
- It has antiseptic and astringent properties.
- Used topically for conjunctivitis, ulcers and acne.
- It decreases sweating, hence used as a component in deodorants.
- Zinc salts are one of the components in calamine lotion, which is used in urticaria and eczema as an antiseptic and antipruritic agent.
2. Silver nitrate; an astringent and antiseptic
- 1% eye drops is used for prophylaxis of conjunctivitis.
- It can also be used as an antiseptic on burns, for removal of warts and oral ulcers.
3. Silver sulphadiazine:
It is very effective against Pseudomonas, hence used topically for preventing infection on burnt surfaces.
- They are used topically as antiseptics. They stain the skin on application.
- Gentian violet and brilliant green are useful in gingivitis, oral thrush, bed sores, chronic ulcers, burns, etc.
- Methylene blue is used in cyanide poisoning.
Surface Active Agents (Surfactants)
They act by lowering the surface tension of solutions. There are two types of surfactants:
1. Anionic surfactants: They are common soaps.
2. Cationic surfactants: They are benzalkonium chloride, cetrimide, and cetylpyridinium chloride.
a. Benzalkonium chloride is used as an antiseptic on the skin prior to surgery and to store sterilized instruments.
b. Cetrimide (cetavlon) is used as a preservative for eye drops and to disinfect instruments.
c. Savlon (cetrimide + chlorhexidine) is used to disinfect thermometers.
Ethylene oxide, formaldehyde, and -propiolactone gases are used for sterilization.
1. Ethylene oxide
- Acts by alkylating the proteins and nucleic acids.
- Highly inflammable and explosive.
- Used for sterilization of heart–lung machines, plastic equipment, sutures, dental equipment and cardiac catheters.
- Nitrofurazone has bactericidal action, but no action on fungi. It is used topically for burns and ulcers.