Pharmacology of commonly used Antiseptics
Antiseptic = agent that causes destruction or inhibition of growth of micro organisms (bacteria, viruses, fungi) on living surfaces such as skin & mucous membranes.
Disinfectant = agent that causes destruction or inhibition of growth of microorganisms (bacteria, viruses, fungi) on non living surfaces (instruments, equipments, pieces of furniture, rooms, etc).
Spores are (usually) not destroyed !!!
Antisepsis = use of chemical solutions for disinfection (prefix: ”anti” = against) e.g. removal of transient microorganisms from the skin and a reduction in the resident flora.
Asepsis = absence of infectious microoorganisms (prefix: ”a” = absence).
Aseptic techniques – aimed at minimising infection
The use of sterile instruments.
The use of a gloved no touch technique.
History of antiseptics
Ignaz Semmelweis (1818 – 1865) Hungarian physician working in Vienna cross contamination → high incidence of death after childbirth.
He made doctors to wash hands in chloride of lime before touching patients.
Dramatically reduced incidence of childhood fever.
Joseph Lister (1827 – 1912) Brittish surgeoncarbolic acid (phenol) for hands and wounds during operationsto maintain aseptic conditions→ aseptic surgery.
Properties of antiseptics/disinfectants
1. Microbicidal activity
2. Non staining & good
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
Disrupt cellular structures and/or processes E.g.
Oxidation of bacterial protoplasm. E.g. H202, Halogens, potasium permanganate
Coagulation (denaturation) of proteins. E.g. Phenols, chlorhexidine, alcohols, Aldehydes
Increasing permeability of bacterial cell Membrane. E.g. Cetrimide, soaps.
Quaternary amonium compounds
Surface antigens metallic salts (Metalls)
Depending on concentration:
Some chemicals can act either as antiseptics or as disinfectants e.g. Phenol solution 0.2% = antiseptic; 1% = disinfectant
Phenol & derivatives
Earliest use (19th century), reference Standard
mechanism: denaturation of bacterial proteins
Uses: disinfection of urine/faeces/pus contaminated surfaces/areas
Extremely irritating, corrosive
Methyl derivative of phenol, less damaging to tissues than phenol.
3-10 times more active used for disinfection of utensils, excreta & for washing hands.
Does not coagulate proteins
Non corrosive, Non irritating to skin.
Commercial 4.8 % solution used for surgical antisepsis
Skin cream and soap: 0.8%
Mouth wash 1% .
Short-acting germicidal effect through release of nascent oxygen, which irreversibly alters microbial Proteins.
Little or no action on bacterial sporesnascent oxygen rendered inactive when it combines with organic matter.
e.g. Hydrogen peroxide solution (3%)
Releases oxygen in contact with catalase on wound surfaces and mucous membranes; effervescent action mechanically helps remove pus and cellular debris from wounds and is valuable cleaning infected tissue.
Broad antimicrobial spectrum (like hydrogen peroxide) + greater lipid solubility.
Effective against bacteria, yeasts, fungi, and viruses (0.001–0.003%)
sporicidal at 0.25–0.5%
Solutions of 0.2% peracetic acid applied to compresses are effective at reducing microbial populations in severely contaminated wounds.
Broad antimicrobial properties,
Effective algicide (0.01%) and virulicide (1%) for disinfection, but concentrations >1:10,000 tend to irritate tissue.
Old solutions turn chocolate brown and lose their activity
Stains tissues and clothing brown (disadvantage)
Halogens & halogen containing compounds
2% iodine + 2.4% sodium iodide (NaI) in 50% ethanol; it is used as a skin disinfectant.
Strong iodine tincture contains 7% iodine and 5% potassium iodide (KI) dissolved in 95% ethanol;
it is more potent but also more irritating than tincture of iodine.
2% iodine + 2.4% NaI dissolved in aqueous solution;
it is used as a nonirritant antiseptic on wounds and abrasions.
Strong iodine solution (Lugol’s solution) contains 5% iodine and 10% KI in aqueous solution.
Potent germicidal effect against most bacteria, viruses, protozoa, and fungi at a concentration of 0.1 ppm,
but much higher concentrations are required in the presence of organic matter.
Alkaline pH ionizes chlorine and decreases its activity by reducing its penetrability.
irritant to the skin and mucous membranes
widely used to disinfect water supplies and inanimate objects (eg, utensils, bottles, pipelines)
sodium hypochlorite solutions (bleach) 2–5% can be used as a disinfectant, and a more diluted form (0.5%) can be used for irrigating suppurating wounds, but it dissolves blood clots and delays clotting
Root canal therapy in dentistry
Acts by disrupting bacterial cell membrane & denaturation of bacterial proteins
Non irritant, more active against Gram + bacteria
Used in for surgical scrub, neonatal bath, mouth wash & general skin antiseptic
Most widely used antiseptic in dentistry 0.12-0.2% oral rinse or 0.5 -1 % tooth paste.
Quaternary amonium compounds
destroy bacteria, fungi & viruses by Altering permeability of cell membrane
Efficiently remove dirt and grease
Widely used as antiseptics & disinfectants for surgical instruments, gloves etc.
Weak antiseptics with cleansing action
Washing with soap and warm water one of the most effective methods of preventing disease transmission
Antiseptic, cleansing agent at 40-90%
Act by precipitation of bacterial proteins
Irritant, should not be applied on mucous membranes, ulcers, open wounds
Aldehydes – Formaldehyde
Also used as sterilization agents!
Used for fumigation
37 % aqueous solution (formalin)
Used for preserving dead tissues
Use as antiseptic restricted due to bad odour & irritation
Glutaraldehyde is a better sterilizing Agents
weak antiseptic, bacteriostatic
used for mouth wash, irrigation eyes glossitis,
Adverse effect: vomiting,abdominal pain on systemic absorption
Metals: metallic salts
Silver ions precipitate proteins + interfere with essential metabolic activities of microbial cells
0.1% aqueous silver solution – bactericidal but irritating
0.01% solution – bacteriostatic
0.5% solution – sometimes applied as a dressing on burns to reduce infection
Colloidal silver compounds – slowly releasing silver ions
more sustained bacteriostatic effect
mild antiseptics, also used in ophthalmic preparations
Gentian violet (Crystal violet)
topical antiseptic; commonly used for
Marking the skin for surgery preparation and allergy testing
Effective against Candida albicans and related infections such as thrush, yeast infections, tinea, etc.
In resource limited settings, , gentian violet is used to manage burn wounds, inflammation of the umbilical cord stump (omphalitis) in neonates, oral candidiasis, mouth ulcers
Active against gram +ve Bacteria gonococci
Store in amber colored bottle
Use chronic ulcers and wounds
Acts by alkylating proteins and nucleic acid
Highly inflammable and explosive.
Used for sterilization of heart – lung machine, plastic equipment, sutures, dental equipment and cardiac catheters.
Not used for fumigation as it is explosive.
40% solution is called formalin.
Formaldehyde solution is used for disinfection of sputum, removal of warts, on palms and soles to treat hyperhidrosis, preservation of anatomical and pathological specimens.
Formaldehyde gas used for fumigation of wards and OT’s rarely for sterilization of heart instruments and gloves.
In dentistry it is used to harden the residual pulp tissue.
Nitrofurazone has bactericidal action on fungi.
It is used topically for burns and Ulcers.