Topical Agents
Rakesh B. Daude
Topical Agents
Protective and
Adsorbents
Antimicrobial
agents
Astringents
Miscellaneous
agents
Topical agents
 Topical agents are the compounds that act locally on skin or
mucous membrane, their action is of different types
depending upon the nature of compound and its chemical
properties and they mainly act by mechanical or physical
mechanism.
 The compounds have very less distinct pharmacological
properties as they are not absorbed in systemic circulation.
Classification
Topical agents are classified according to their main action.
1. Protective :
Ex: Zinc stearate, Zinc oxide
2. Adsorbent and demulcents:
Ex: Talc, Silicone polymer, Titanium Dioxide, Calamine
3. Antimicrobial agents: It acts by Oxidation, Halogenation and Protein precipitation
mechanism.
Ex: Hydrogen peroxide, Potassium permanganate, Chlorinated lime, Iodine and its
preparation, Boric acid, Borax and Silver nitrate.
4. Astringent: These compounds bring about mild protein precipitation.
Ex: Alum, Zinc chloride, Zinc sulphate
5. Miscellaneous compounds. These compounds mainly contain Sulphur and Sulphur
compounds. It is topically used as antibacterial. It also acts as fungicide, parasiticide, and
in the treatment of various skin diseases.
Ex: Sulphur Ointment, Selenium Sulphide
Classification
1) Protectives and adsorbents: e.g. Talc, Calamine, Zinc Oxide,
Titanium Dioxide, silicone polymers.
2) Anti-microbial agent: They are further classified based on
their mechanism of action:a) Acting by oxidation e.g. Hydrogen peroxide solution,
potassium permanganate.
b) Acting by halogenation e.g. Iodine and iodine preparation,
chlorinated lime.
c) Acting by protein precipitation e.g. Boric acid, Silver and
Silver compounds, Mercury compounds.
3) Astringent: e.g. Alum, Aluminum chloride, Zinc Sulphate, Zinc
chloride
4)Miscellaneous agent: e.g. Sulphur and sulphur compounds,
Selenium Sulphide.
Protective and Adsorbents
Protectives and adsorbents are the chemical agents used internally
in treatment of disturbances of gastrointestinal tract like diarrhea &
dysentery because they are water insoluble substances and they
form a protective coat on the mucosal membrane and offer
mechanical protection, furthermore, they adsorb bacterial toxins
which are believed to stimulate flow of electrolytes into intestine
resulting in watery stools.
Examples: Bismuth Sub carbonate, Kaolin etc.
Note - Some protectives and adsorbents are used externally.
Kaolin
Properties of Kaolin• It occurs as a soft white or yellowish white powder, odourless and has clay like taste.
• When moistened with water, assumes a darker color & develops a marked claylike
odor.
• It is insoluble in water, in mineral acids and in solutions of alkali hydroxides.
• Chemically, it is practically inert, since it is insoluble in all the common solvents.
Uses• It is used in mixtures intended for treatment in dysentery, diarrhea and for
symptomatic treatment of colitis, cholera etc.
• It is employed in the treatment of food and alkaloidal poisoning as it adsorbs toxins.
• It also finds use in dusting powder, cosmetic preparations and is an ingredient of
Kaolin poultice.
• For the internal use, it is mainly the light Kaolin which is employed.
• It is used as a drying agent for moist sores and infections
e.g. weeping eczema, as weeping ulcers.
• It is also used as a clarifying agent.
Zinc oxide :
Mild astringent
Weak antimicrobial & topical antacid
It is also used in some bandages & adhesives
Titanium dioxide
It is used to prevent sunburn in the form of suntan preparations
It is used as a white pigment in lotions & cosmetic preparations
As a skin protective & for the relief of pruritus
For application to the exudative dermatoses.
Talc
As a skin protective dusting powder
As a base for medicated dusting powder
Used as a lubricating agent in the tablet manufacturing
Also used as a filtering aid
Kaolin:
Light kaolin is used as an intestinal adsorbent in various enteritis
It is used in the symptomatic treatment of gastrointestinal conditions associated
with diarrhoea
It is also used as a clarifying agent
Astringents
 Astringents are the agents which cause local or
surface or mild protein precipitation when applied
to damaged skin or mucus membrane.
 This action may be on mucosal membrane when
taken internally or on skin for topical use.
 Astringents when applied topically cause
precipitation of protein of surface cell by
coagulation.
 The action depends upon the extent of penetration
of agent and the type of chemical action resulting
with protein.
 e.g. Alum and Zinc Sulphate.
Astringents- Uses
 It causes constriction of small blood capillaries, and promotes
the coagulation of blood hence used as styptic (able to stop
bleeding).
 It decreases the volume of exudate from wounds & skin eruption
& thus can be used in acne &pimples.
 Astringent causes constriction of skin pores & destroy body odor,
hence used as an antiperspirant & deodorant.
 Higher concentration of astringent is used to remove warts
(extra growth of cell on skin).
 It promotes healing and toughens the skin.
 It restricts blood flow to the surface of mucous membrane hence
astringent decreases inflammation.
Astringents-Alum
Properties:
1. It occurs as colourless, transparent or granular crystals with a
sweet astringent taste.
2. When heated slowly it melts in its water of crystallization.
3. At 200°, it loses its water of crystallization and becomes
anhydrous.
4. It is soluble in water but insoluble in alcohol.
Uses:
1. It is used as a topical astringent.
2. Its 0.5 to 5% solution is useful as an antiseptic and commonly
used for local styptic action.
3. Alum either as a solid or as a solution is used as a haemostatic for
superficial abrasions, cut an ulcers.
4. Its dilute solutions have been used as mouth-washes or gargles,
but their high acidity may damage the teeth.
Anti-microbial agents
Antimicrobials are the chemical agents used to destroy
or inhibit the growth of pathogenic Microorganisms.
Antimicrobial is a broad terminology describing
activity against microbes.
Mechanism of action: Inorganic compounds generally
exhibit antimicrobial action by, either of the three
mechanisms viz.
(i) Oxidation
(ii) Halogenation
(iii) Protein binding or precipitation.
Anti-microbial agents-Oxidation
 Compounds acting by this mechanism belong to class of
peroxide, peroxyacids, Oxygen liberating compounds like
permanganate and certain Oxo-halogen anions.
 Microorganisms require protein for their growth. Various
reducing groups are present in proteins which are oxidized
by oxidizing agents.
 They act on proteins containing sulfhydryl group and oxidize
free sulfhydryl to Disulphide bond and inactivate its function.
 Hence change in molecular shape of protein leads to
destruction of protein.
 e.g. Hydrogen peroxide, Potassium permanganate, nonmetals act by this mechanism.
Anti-microbial agents-Halogenation
 Proteins are made up of different amino acids and it contains
peptide linkage or peptide chain.
 Some antimicrobial agents like hypochlorite’s or compounds
containing or liberating chlorine or iodine cause chlorination
or iodination at peptide linkage of primary &secondary
structures present in protein, leading to change in molecular
shape of protein, and destruction of protein.
 E.g. Iodine & iodine preparations, Chlorinated lime, Sodium
Hypochlorite
Anti-microbial agents-Protein ppt
 Many metals in their cation form exhibit protein binding or
protein precipitation.
 The nature of interaction with protein occurs through polar
group of protein which acts as ligands and metal ion acts as
Lewis acid.
 The complex formed may be a strong chelate leading to
inactivation of protein.
 This action in general is non-specific.
 Protein precipitants do not distinguish between the protein
of microbes and that of host.
 Germicidal action results when the concentration of ion is
such that reaction is restricted largely to the parasite cell.
Anti-microbial agents-Protein ppt
 Protein structure contains many polar groups & groups
having lone pair of electrons.
 Some antimicrobial agents containing metal ions form
complexes with polar groups or groups having lone pair of
electrons leading to precipitation of enzyme proteins.
 e.g. Silver nitrate, Mild silver protein, Mercury & Mercury
compounds like Yellow Mercuric oxide, Ammoniated
mercury, Boric acid, Borax, IB, IIB group metals- Cu(II), Ag(I),
Zn(II), Hg(II) etc.
Thank You