Introduction Definition Of Tablet Various Factors affecting Strength of Tablet

1. Seminar on…
Various Factors affecting
strength of Tablets
By…
Mr. Kailash V Vilegave

2. Contents
 Introduction
 Definition Of Tablet
 Various Factors affecting Strength of Tablet
 References

3. Introduction
 Tablets require certain amount of Strength
to withstand Mechanical shocks of
Handling during Manufacturing, Packaging
& Shipping.
 In order to show desired response each
Tablet should posses optimum Strength.

4. Definition
 Tablets are unit solid dosage form
containing Medicament/Medicaments with
or without suitable excipients.

5. Factors affecting Strength of
Tablets
 Moisture content
 Lubrication
 Particle size & Shapes

6. Moisture Content
 A small proportion of Moisture content is desirable for
the formation of a coherent Tablet.
 The amount of moisture present on the Powder surface
is just sufficient to fill the remaining voids in the bed.
 Further increase in Compression force results in this
water being squeeze out to the surface of Tablet.
 This expelled Moisture may act as a lubricant at die wall,
but It causes material to stick to punch forces.

7.  At low moisture content there will be increase
in die wall friction due to increased stress,
hence the Tablet hardness will be poor.
 At high moisture level the die wall friction is
reduced owing to lubricating effect of moisture.
 At further increase in moisture content there will
be decrease in Compact strength due to
reduction in Interparticulate bond.

8.  Generalised plot of
Tablet Strength Vs
Moisture content of
granules

9. Lubrication
 Lubricants are commonly included in Tablet
formulations in order to reduce.
 Die wall friction.
 To improve flow properties & Antiadherant
properties.
 However their presence may cause undesirable
changes in Tablet properties.

10. Effect of Lubrication on Tablet
Strength
 Shotton & Lewis investigated the effect of Mg. Stearate
on the strength of Tablet of crystalline materials & two
simple granulation without binders.
 They found that Lubricant decrease the strength of all
Tablets.
 The softening of Tablet by lubricants has been reported
by Strickland who observed that Mg. Stearate & other
Lubricants added as dry powder to granules, They
appeared to adhere & form a coat around individual
granules.

11.  Bolhuir showed that Mg. Stearate forms an
adsorbed lubricant film around host particles
during the mixing process.
 The Lubricant film interfere with the bonding
properties of host particle by acting as a physical
barrier.
 This can be seen when the Tablet crushing
strength is plotted as a function of the Log of the
mixing time with the Lubricant.

12. Film formation of Lubricant on the
Host particle.

13.  The magnitude of the effect of Lubricants
on crushing strength is depended on large
no. of factors.
 Nature & properties of the Tablet
ingredients & Processing condition.

14. Film formation of Lubricants during
mixing
 When a powdered Lubricant is added to a Tableting
blend & submitted to a mixing action it is distributed as
free fraction.
 Prolonged mixing time will transfer more Lubricant from
free fraction to the surface film.
 The phenomenon of decrease in strength with an
increase mixing time of Tablet ingredients with
Lubricants is caused by formation of this Lubricant film,
which interfere with the binding of the particles.
 The in crushing strength has been attributed to weaker
bonds after compression between Lubricant – Lubricant
molecules rather than strong excipients bonds.

16.  A significant reduction in crushing strength
has been found during mixing of excipients
with hydrogenated oils, glycerides & PEG.
 Lubricants are Hydrophobic materials,
poor selection or excessive amounts can
result in water proofing the Tablets.
 Lubricants have been added to the
granulating agent in the form of
Suspension or Emulsion.

17. Material Type Conc In
Granule
s w/w
Boric Acid E,L 1-5
Collodial E,G 0.1-0.5
Silica
Magnesium E,L,I 0.1-1
Sterate
Stearic Acid E,I,L 0.1-2
Talc E,G 1-5

18. Effect of Particle Size on strength
of Tablet
 The shape of a particle is a complex
characteristic and its importance in relation to
powder properties is therefore difficult to assess.
 Generally particles with optimum size will give
good strength for tablets.
 If the particle size is large(200-250µm)then they
have a tendency to flow better than the smaller
particles because they have greater mass.

19.  Where as smaller particles may create mixing
problems because surface area is more &may
give rise to strong electrostatic forces as a result
of processing and or Interparticulate friction from
movement.These may prevent the desired
distribution of these smaller particles.
 As the particle size approaches 10µ & below
weak polarsing electrical forces called
vandarwalls force or cohesive forces affect the
flow of powder.

20.  Smaller particles have larger surface area
&when these are expose to atmosphere may
prone to oxidation, moisture adsorption take
place which effect the strength of tablet.
 Very large particles often exist as agglomerates
of a small crystals on compression these
agglomerates breakdown into small units.

21. EFFECT OF PARTICLE SHAPE
ON STENGTH OF TABLETS
 Particle shape affects powder inter-
particulate friction &consequently the flow
properties of powder
 General particle shapes and their effect on
powder flow as follows
 Spherical particles
 Ablong shaped particles
 Cubical shaped particles
 Irregular shaped particles

22. REFERENCES
 The Theory and practice of industrial pharmacy
by Leon lachman.Herbert a Lieberman Joseph
kiang third edition.
 Pharmaceutics: The science of dosage form
design by a Michael E. Aulton.
 Remington “The science &practice of pharmacy
volume1,19th edition 1995
 Physical pharmacy By Alfred martin, james
Warrick Varghese Publications.
 www.google.com