Antiseptics and disinfectants - general discussion, classification, modes of action, drugs as per syllabus for diploma in pharmacy

1. Antiseptics
and
Disinfectants
-Ambareen Fatima Ahmed
As per syllabus prescribed by PCI for diploma in pharmacy.

2. Antiseptics: These are chemical agents that destroy micro-organisms
on living surface without causing any injurious effect to the applied
surface.
Antiseptics are applied to,
• The unbroken skin or mucous membranes.
• To burns.
• Open wounds to prevent sepsis.
Disinfectants: These are chemical agents that destroy micro-organisms
on inanimate surface or reduces the number of micro-organisms to a
safe level on an inanimate (non- living) object.
Disinfectants do not necessarily kill all micro-organisms but reduce
them to a level which does not harm health.
Both, antiseptics and disinfectants are used to inhibit the growth or kill
pathogenic micro-organisms in the vegetative or non-sporing stage.

3. Properties of good
antiseptics /
Disinfectants
Cidal Non-staining
Active against all
or most
pathogens
Active in presence
of pus, blood and
exudates
Rapid acting
Non irritating /
Non-corrosive
Non absorbable
Non- sensitizing Chemically stable Cheap

4. Mechanism of action of antiseptics
1) Oxidation of bacterial protoplasm
E.g.; H2O2, KMnO4
2) Co-agulation (De-naturation) of bacterial proteins
and disrupt cell membranes
E.g.; Phenols, Alcohols, Aldehydes
3) Detergent like action
E.g.; Cetrimide, Soap

5. Classification
1) Phenol derivatives
E.g.; Phenol, Cresol, Chlorocresol,
Chloroxylenol
2) Oxidizing agents
E.g.; Hydrogen peroxide
3) Halogens
E.g.; Iodine, Chlorine
4) Alcohols
E.g.; Ethanol, Iso-propyl alcohol
5) Aldehydes
E.g.; Formaldehyde, Acetaldehyde
6) Cationic surfactant
E.g.; Benzalkonium chloride,
Cetrimide
7) Biguanides
E.g.; Chlorhexidine
8) Dyes
a) Acridine derivatives:
E.g.; Proflavine, Acriflavine
9) Miscellaneous
E.g.; Nitrofurantoin

6. A) Phenol and its derivatives
1) Phenol (Carbolic acid, Hydroxy benzene, Benzenol)
P.P.
i) Colourless/ Faintly pink needle shaped
ii) Characteristic odour
iii) Deliquescent
iv) Soluble in alcohol, liquid paraffin, glycerol.
C.P.
i) Acidic in nature
ii)Dissolves in solution of alkali to form phenolate ion.
iii) Undergoes nitration reaction
Stability and Storage: Unstable and turns pink on exposure to
atmospheric air. Stored in air tight containers, protected from light in a
cool place (below 15°C)
Uses:
1) Antiseptic and disinfectant against wide range of microbes.
2) Liquid phenol is used in dentistry and as an analgesic in 5% solution
to de-sensitize the pulp of decidous teeth.
Mechanism of action:
Acts by denaturing bacterial proteins.
Liquified phenol:
It contains 80% phenol and 20% water.
2) Chlorocresol
IUPAC name: 4-Chloro-3-methylphenol
P.P. &C.P.
i) Pink to White crystalline solid ii) Phenolic odor
iii) Hygroscopic iv) Soluble in alkali and organic
solvents v) Corrosive to metals and forms complex
compounds with metal vi) Contains hydroxyl
group and hence behaves as an acid.
Stability and storage: Aqueous solution turns yellow on
exposure to light and air. Well closed protected
from light.
Uses:
1) Antibacterial
2) Antifungal
3) Antiseptic and disinfectant
4) Pharmaceutical aid
5) In veterinary medicine

7. 3) Chloroxylenol
P.P. &C.P.:
i) White / cream colored crystalline powder
ii) Phenolic odor iii) Soluble in organic
solvents.
Stability and storage: Stable when
exposed to sunlight and humidity.
Uses:
1) Antiseptic: In solution form , used on skin
wounds and other topical preparations.
2) Personal care products
Formulation: Dettol
4) Hexachlorophene
P.P. &C.P.:
i) White, pale buff color powder ii)
Crystalline iii) Phenolic odor iv) Insoluble in
water v) Soluble in alcohol, ether an NaOH
Stability and storage: Stored in air tight
containers protected from light.
Uses:
1) Antiseptic
2) Used in soaps and creams (0.23 to 3%)
3) For disinfection of hands before surgery
in a concentration of 3% .
4) Veterinary use in dog shampoo.

8. 5) Formaldehyde
40% solution of formaldehyde is called as
formalin.
P.P. &C.P.:
i) Clear, colorless liquid
ii) Characteristic, pungent, irritating odor.
iii) Miscible in water and alcohol
iv) Readily oxidized by atmospheric oxygen into
formic acid.
v) It is a reducing agent.
Stability and storage: Stored in air tight
containers between 15- 25°C.
Uses:
i) Aqueous solution of formaldehyde is used as
disinfectant.
ii) Disinfection of rooms and instruments.
iii) A 4% solution is used to preserve biologic
tissues.
6) Benzalkonium chloride
Chemically it is alkyl benzyl-
-dimethyl ammonium chloride.
It is a quaternary ammonium cationic surfactant.
P.P. &C.P.:
i) White/ yellowish white powder ii) Aromatic odor
iii) Extremely bitter
iv) Hygroscopic
v) Soluble in alcohol, water and ether
vi) Aqueous solution are alkaline and froths on shaking.
v) 1% solution is slightly alkaline to litmus.
Stability and storage: Sensitive to light.
Stored in air tight containers, protected from light. Should
not be stored in rubber containers.
Uses: i) Antiseptic for wounds, infected skin surfaces in very
dilute aqueous solution.
ii) To disinfect surgical instruments.
iii) As a very dilute solution, it is used for irrigation of
bladder, urethra, vagina, throat and eye-wash.

9. 7) Cetrimide
P.P. &C.P.:
i) White / cream colored free flowing powder.
ii) Faint characteristics odor iii) Soapy bitter
taste iv) Soluble in water, alcohol and ether.
Stability and storage: In an air tight containers.
Uses: i) Anti-infective
ii) Sterilization of skin prior to surgeries.
iii) Seborrhea of scalp (1-3% solution) in the
form of shampoo.
Brand names:
1) CETAVLON CONCENTRATE: Cetrimide 20%
2)SAVLON LIQUID ANTISEPTIC: Chlorhexidine
gluconate: 1.5% + Cetrimide 3%.
3) SAVLON/CETAVLEX CREAM: Chlorhexidine
HCl 0.1% + Cetrimide 0.5%.
4) SAVLON HOSPITAL CONCENTRATE:
Chlorhexidine gluconate: 7.5% + Cetrimide
15%.
8) Proflavine
IUPAC name: Acridine-3,6-diamine
P.P. &C.P.:
i) Orange red - brown red crystalline powder. ii)
Soluble in water, ethanol. iii) Insoluble in benzene
and ether.
Stability and storage: Air- tight container,
protected from light.
Uses: i) Slow acting antiseptic.
Used to treat infected wounds/ burns of external
ear, mouth, throat and skin.
It stains skin which can be washed with very
dilute acidic solution.

10. 9) Nitrofurantoin
P.P. &C.P.:
i) Lemon yellow colour crystals.
ii) Odorless
iii) Bitter after-taste
iv) Slightly soluble in water
v) Insoluble in alcohol
Stability: It is sensitive to heat and I discoloured upon exposure to light. Decomposed upon
contact with metals.
Storage: Stored in air tight containers protected from light below 25°C.
Uses:
i) Used to treat acute urinary tract infections(UTI).
ii) Bacteriostatic at 5-10 µg/ml and bactericidal at 100 µg/ml.
Brand names:
1) Tablet Furadantin 50/100 mg.
2) Tablet Trifuran 50 mg.
3) Capsule Urifast 25 mg immediate release and 75 mg SR.