(Mode of Action of Drugs)
PharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamics
Chapter
1.4
Chapter
12.1
Antiseptics &
Disinfectants
These are the agents which inhibit or kill
microbes on contact. Conventionally
- Antiseptics are used on living
surfaces. - Disinfectants are used for inanimate
objects.
The practical distinction of these two
agents is on the basis of a growth inhibiting
or direct lethal action. There are
concentration dependent. Germicide covers
these two category. Potency of germicide is
generally expressed by its “phenol
coefficient or Rideal Walker (RW)
coefficient” – “which is the ratio of the
minimum concentration of the test drug
required to kill a 24 hour culture of B. typhosa
in 7.5 minutes at 37.5°C to that of phenol
(as standard) under similar conditions.”
In dentistry, they are used for
sterilization of certain instruments and
prevention and treatment of dental plaque
and peridental diseases. They are also used
in root canal therapy (RCT), treatment of
acute necrotizing gingivitis and other
infective oral conditions. Antiseptics and
disinfectants are also used as ingredient in
various dentifrices.
Factors which Modify the Activity of
Germicides- Temperature & pH.
- Period of contact with the microor-
ganisms. - Nature of microbes involved.
- Spectrum of activity of majority of
antiseptic disinfectants is wide re-
flecting non selectivity of action.
However, some are selective e.g.
hexachlorophene, chlorhexidine,
quarternary ammonium antisep-
tics, gentian violet, acriflavine are
more active for gram +ve than gram
–ve. Silver nitrate is highly active
against gonococci and benzoyl
peroxide against P. acnes.
- Spectrum of activity of majority of
- Size of inoculum.
- Presence of blood, pus & other organic
matter.
Mechanism of Action (Cidal or
Inhibiting Action)
i. Oxidation of bacterial protoplasm.
ii. Denaturation of bacterial proteins
including enzymes.