tableting

Question 1

what are compressed tablets

Answer 1

are solid dosage forms prepared by
compaction of a formulation containing the drug substance
(API) and excipients selected to aid processing (such as
lubricant to prevent sticking) and improve the properties of the
product (such as disintegrant)

Question 2

what are the advantages of tableting

Answer 2

1. Tablets can be produced at a much greater rate than any
   other dosage form.
2. Tablet is a dry dosage form thus promoting stability, in
   general; tablets have shelf lives measured in years.
3. Tablets are easy to dispense.
4. Tablets are readily portable and consumed dosage form.
5. If property prepared, tablets provide a uniformity of dosage
   greater than a liquid medicine.
6. Tables provide a versatile drug delivery system. Whilst most
   tablets are intended to be swallowed intact, others may be
   used for sublingual and buccal administration.

Question 3

what are the qualities of a well prepared tablet

Answer 3

1. It should contain the stated dose of drug within permitted
   limits.
2. It should be sufficiently strong to withstand the stresses of
   manufacture, transport and handling, so as to reach the
   patient intact.
3. It should deliver its dose of drug at the site and at the speed
   required.
4. Its size and appearance should not detract from its
   acceptability by the patient.

Question 4

what are the 3 important properties the compound should have in order to prepare tablets

Answer 4

1. The particles must be sufficiently free-flowing → because they
   must uniformly flow into the relatively small volume in the die in
   a very short time → proving uniformity of weight
2. The particles, when subjected to a force from the punches,
   cohere to form a compact of adequate strength (i.e. particles
   must be easy to be compressed)
3. Whilst the particles must cohere, adhesion by the tablet to the
   punches and dies must be avoided; otherwise damage to
   both tablet and press will occur when attempts are made to
   remove the tablet from the die.

Question 5

what are the different types of tableting

Answer 5

a) Direct compression (DC): powder compressed and directly
converted into tablets

b) (Wet or dry) granulation, followed by compression:
1. Powder transformed into granules
2. Granules compressed into tablets

Question 6

The formulation of a tablet is governed by a number of factors, name them

Answer 6

1. The drug substance involved, its chemical and physical
   properties and route of administration
2. The manufacturing process to be employed (direct
   compression vs granulation, followed by compression)
3. The method by which the tablet is to be used, i.e.
   swallowed whole, chewed, dissolved in water etc.

Question 7

what are the factors that effect the drug substance

Answer 7

a) Site and extent of absorption of drug in the gastrointestinal
tract.
b) Stability of the drug to heat or moisture
c) Compatibility of the drug
d) Dose of the drug
e) Solubility of the drug

Question 8

what is the solution for the Site and extent of absorption of drug in the gastrointestinal
tract problem

Answer 8

A similar solution may be adopted for substances which
undergo extensive first-pass hepatic metabolism, e.g.
glyceryl trinitrate sublingual tablets.

Question 9

what to do in the case of inStability of the drug to heat or moisture

Answer 9

Substances which would undergo appreciable degradation in
the conditions of the wet granulation process obviously cannot
be made into tablets by this means. In such cases dry
granulation or direct compression must be used, or another
dosage form chosen (i.e. capsule).

Question 10

what will decide the amount of filler

Answer 10

The dose of the drug will decide the necessity of the filler
(i.e. diluent)→ low potency drug could be produced
without adding a filler.
However…..
If a filler is not used, then there is little possibility of the direct
compression method of tablet preparation being suitable
for this tablets → this is because it is unlikely that the drug
as such will have good enough flow and compaction
properties for undergoing direct compression.

Question 11

compare between direct compression and granulation then tableting (flow, time,cost, properties)

Answer 11

1. Flow:
   Granulation improve the flow of powders, proving improved
   uniformity of weight for the tablets.
2. Compaction properties:
   Granules are more easily to be compressed into hard tablets.
   Therefore, for difficult formulations, there is always a clear
   advantage in using granulation (followed by compression), rather
   then direct compression.
3. Time
   Direct compression involves only two steps: dry mixing of
   powdered drug and excipients; compression of the mix.
   Wet granulation + compression includes more steps to convert a
   drug into a final tablet.
   Direct compression is obviously a more rapid overall process.
4. Cost
   Direct compression is in theory cheaper, as it involves less steps and
   therefore less equipment and less material handling.

Question 12

 In the rare case of free-flowing, easily to compress powders, direct
compression becomes the obvious choice.
 In case of poorly flowing and/or difficult to compress powder mixes,
one of these two choices should be evaluated, name them

Answer 12

1. Granulation (followed by compression);
2. Direct compression using special grade of excipients (potentially
   very expensive) that can considerably enhance powder flow
   and/or compaction properties.

Question 13

what are the different types of tablets

Answer 13

1. Conventional immediate release tablet
2. Tablets to be dissolved in water before use
3. Chewable tablets
4. Lozenges
5. Buccal and sublingual tablets

Question 14

how to prepare immediate release tablets

Answer 14

wet granulation process then:
A granulating agent must be chosen to give granules which
compresses to form tablets of acceptable strength.
A lubricant is chosen so as to enable easy ejection from the die.
Care must be taken not to add too much lubricant: this would
both prolong disintegration time and reduce tablet strength.
A sufficient concentration of disintegrant should be used.

Question 15

how to prepare tablets meant to be dissolved in water (effervescent tablets)

Answer 15

a) All ingredients should be soluble
b) The preparation cannot be based on the use of
aqueous-based granulating agent (→ to prevent
effervescence during the granulation process). Hence, a
non-aqueous granulation or a totally dry method of tablet
production is necessary.

Question 16

what are effervescent tablets

Answer 16

an acid (usually tartaric or citric acid) reacts with a bicarbonate
(usually sodium or potassium) on the addition of water to
produce carbon dioxide

Question 17

how to formulate chewable tablets

Answer 17

Chewable tablets are often used for children and geriatric
patients who have difficulty in swallowing tablets.
Since the tablet is not swallowed and it is disintegrated in the
mouth, the taste of the preparation is important in this case.
Taste masking can be achieved by choice of diluent
Taste masking becomes more difficult with drugs of
unpleasant taste, particularly if present in high dose.
→A frequently used diluent is mannitol, which has a pleasant
cooling sensation in the mouth, effectively masking many
taste problems.

Question 18

how to prepare lozenges

Answer 18

Tablets that dissolve slowly in the mouth and so release the drug
dissolved in the saliva (e.g. used for local medication of mouth or
throat). Such tablets:
a) Do not contain disintegrants
b) Contain fillers of pleasant taste
c) Must be formulated to obtain hard tablets, so to dissolve slowly
in the mouth

Question 19

how to prepare sublingual and buccal tablets

Answer 19

Sublingual and buccal tablets are designed for drug release in
the mouth, followed by systemic uptake of the drug. Drug
absorbed in such way have the advantage of skipping the first
pass metabolism in the liver.
• These tablets should dissolve rapidly. Hence a highly soluble
formulation must be selected (not hard and porous tablets are
often formulated).

Question 20

what is powder compression

Answer 20

defined as the reduction in volume of a
powder owing to the application of a force. Because of the
increased proximity of the particle surfaces during compression,
bonds are formed between particles which provides coherence
to the powder and a compact is formed.

Question 21

what are the punches used in tableting

Answer 21

1. The lower punch: the tip of which
   moves up and down within the die, but
   never actually leaves it.
2. The upper punch, which descends to
   penetrate the die and apply the
   compressive force and then goes back
   up to permit ejection of the tablet

Question 22

what are the stages of tableting

Answer 22

1. The lower punch falls within the die, leaving a cavity into
   which particles can flow due to gravity (Filling).
2. The upper punch descends, and the punch tip enters the
   die. Further punch movement applies the compressive
   force to the particles, which aggregate to form a tablet
   (Compression).
3. The upper punch withdraws from the die and simultaneously
   the lower punch rises until its tip becomes level with the top
   of the die. The tablet is thus ejected from the die and
   removed from the tablet press (Ejection).

Question 23

what are the types of tablet press machines

Answer 23

1. The single-station or single-punch press.
2. The multi-station rotary press.

Question 24

what are the main parts of the single punch

Answer 24

Hopper for holding the granulation
Hopper shoe: it is responsible for feeding the granulation when it
is above the die.
Upper and lower single punches:
 The lower punch
 The upper punch
Die fixed in a disk.

Question 25

how does the single punch operates

Answer 25

Pre-setting filling volume:
First, before starting the whole compression cycle (filling,
compression, ejection), the weight of tablets can be adjusted by
lowering the lower punch using the capacity regulating screw.
Lowering the punch to a preset point leads to higher powder
filling volume and more tablet weight.
The tablet weight also depends on the granulation or powder
density; the higher the density the higher the weight at the same
depth

Filling stage:
At this stage, the hopper shoe moves forward to be right above
the die allowing for die filling.
At the same time, the lower punch is lowered to the preset point
to form a cavity in the die to provide a volume corresponding to
the correct fill weight for the tablet. While the upper punch is in
the raised position

Compression stage:
After filling, the hopper shoe moves aside away from the die
cavity.
The lower punch remains stationary, while the upper punch
comes down to the die to compress the powders/granules into a
tablet.

Ejection stage:
After compression, the upper punch moves upward and
simultaneously the lower punch moves upward to eject tablet
out of die.
At this time the shoe comes back over the die thus pushing the
ejected tablet into a collector.
Now the lower punch is lowered for another filling and the three
stages are repeated.

Question 26

what are the main parts of the multi-station press

Answer 26

there are a number of dies and sets of punches (up to 60 or
more)
 Dies are hold in a rotating table, called die table.
Both die table and punches rotate
together so that one die is always
associated with one pair of punches
Upon rotation: filling, compression and
ejection happen simultaneously.
The vertical movement of the punches is
controlled by fixed cam tracks

Question 27

what is the operation of the multi-station tablet press

Answer 27

Filling
 From the hopper the powder flow by gravity into the
die table.
 The powder is fed into the die by feed frame.
 For filling to happen, lower punches is lower to the
lowest position by the cam track (L2-L7). This allows dies
to overfill with powder.
 Before lower punches leave the feed frame, they rise
slightly to expel excess granules giving the desired
amount for tablet weight (L8).
 Weight of tablets can be controlled by capacity
adjuster which allows for lowering or rising the position
of this cam; lowering cam leads to more tablet weight
and vice-versa.

2. Compression:
    After die filling, lower punches leave the feed frame
   and travel over cam (above lower compression
   roll). Thus, the lower punch is raised into the die (L9-
   L13).
    Simultaneously, the upper punches ride beneath
   the upper compression roll. These will cause the
   upper punch to enter into the die to certain
   distance (U9-U13).
    The powder or granulation inside die will be
   squeezed and compacted.
3. Compression:
    After die filling, lower punches leave the feed frame
   and travel over cam (above lower compression
   roll). Thus, the lower punch is raised into the die (L9-
   L13).
    Simultaneously, the upper punches ride beneath
   the upper compression roll. These will cause the
   upper punch to enter into the die to certain
   distance (U9-U13).
    The powder or granulation inside die will be
   squeezed and compacted.

Question 28

what is the output of the multi-station press

Answer 28

Outputs of over 10 000 tablets per minute can be achieved
by this type of press.
The output is governed by the speed of rotation of the table
and the number of sets of punches.
This means that the largest tablet presses, operated at high
speed can produce over 1 million tablets per hour.

Question 29

what can the tablets have

Answer 29

 Break-marks to facilitate breaking of
tablets in a controlled way to ensure
reproducible doses.
 Marking for identification of a
preparation:
 Embossed markings are raised on the
tablet surface
 Debossed marking indented into the
tablets (more common)

Question 30

what are the mechanisms of powder compaction

Answer 30

1) Repacking or rearrangement of particles:
the particles move relative to each other, with finer particles
entering the voids of air between larger particles.
→ the density of the bulk of powders (or granules) increases.
→ In other words, the particles undergo rearrangement to form
a less porous structure.
The repacking increases area of contact between particles for
bonding.
* Repacking mainly occurs at beginning of the compression,
therefore at low compression force.

2) Deformation:
Change of particle shape, due to the applied pressure.
Deformation increases the contact points between particles
for bonding (i.e. deformation of spherical particles to
rectangular particles lead to more contact points for
bonding).

3) Fragmentation
Under higher pressure, the deformed particles may fragment
(i.e. break into pieces), with an increase in new, clean
surfaces that are potential bonding areas.
Fragmentation is a further densification process (i.e. particles
closer to each other and less air voids), as when fragments
form they can infiltrate into the voids of air between particles.

Question 31

what are the types of deformation

Answer 31

Deformation would be either:
 elastic (reversible).
 plastic (irreversible).
Elastic deformation involves full recovery of particles’ shape
spontaneously upon the release of pressure.
On the other hand, if the deformation was not recovered
completely, the deformation is called plastic deformation.
Both plastic and elastic deformation may occur, although
one type is predominant. This depends on the nature of
materials1 and compression force2 and time3.

Question 32

what are the mechanisms of bonding in tablets

Answer 32

1. Intermolecular (attractive) forces
2. Formation of solid bridges

Question 33

During the compression, the repacking, plastic deformation and
fragmentation of particles all result in?

Answer 33

1. increased interparticulate contact area
   → ↑ interparticulate contact area means ↑ surface area for
   attractive forces between particles
2. Reduced distance among particles
   → The closer the particles are to each other the stronger the
   attractive forces.

Question 34

how do solid bridges form

Answer 34

 During compression some amorphous or low-melting point
materials may temporary soften or melt. Therefore, solid
bridges between particles might be formed in this way.
 Many binders or adhesives form bonds between granules by
this mechanism

Question 35

what is compactabillity

Answer 35

the ability of the powder mass to
form a compact (i.e. tablet) of a certain mechanical strength at a
given compaction pressure. In other words it refers to its capability
to form a coherent, strong tablet

 A powder mix suitable for compression should produce hard
tablets without applying excessive compaction forces.

Question 36

poor compactability leads to ?

Answer 36

1. low mechanical strength (i.e. low tensile strength and low
   resistance to attrition) → this means that tablet would not be
   able to withstand the mechanical stresses during handling or
   packaging
2. high tendency to cap or laminate

Question 37

what are the factors affecting powder compactability

Answer 37

1. Materials and formulation factors (i.e. physical/mechanical
   characteristics of the particles compressed). They can be
   controlled by:
   a) Choice of excipients and ratio of drug/excipients
   b) how particles are combined (i.e. direct compression, dry
   granulation, wet granulation)
2. Processing factors (i.e. choice of tablet press and operation
   conditions).
3. Environmental factors (i.e. the relative humidity).

Question 38

what are the advantages of granulation

Answer 38

1To make the powder bind better when compressed.

2To make the powder flow better.

In the latter sense, the granulation process is a particle size
enlargement, the larger the diameter of the particle (usually 
500µ) the better the flow.
The flow of granules is extremely important, because it controls
the filling of the die cavity.

Question 39

if the powder does not flow properly
into the die
then either

Answer 39

(i) the powder in the hopper will bridge preventing the flow
through the hopper shoe or
(ii) an empty corner will be created in the die-punch cavity.
In the first case, the flow will stop or become very slow (i.e. dies
remain empty!)
In the second case, imperfect and low weight tablets will be
produced.

Question 40

what are the excipients used in tablets

Answer 40

Diluents / Fillers
Binders
Disintegrants
Glidants
Lubricants

Question 41

what are the diluents\ fillers

Answer 41

‘inert’ substances which are
added to the active ingredient in sufficient quantity to make a
reasonably sized tablet

Question 42

what are the properties of the diluents

Answer 42

1. Cheap
2. Inert
   Although diluents are normally thought as inert ingredients,
   they can significantly affect the biopharmaceutical
   properties of the final tablet.
   For example, calcium salts interfere with the absorption of
   tetracycline
3. Non-hygroscopic:
   Hygroscopicity may affect the tablet in different ways.
    It may present a degradation source for moisture sensitive
   drugs.
    Hygroscopicity also affects the ease of drying: hygroscopic
   ingredients are not easily dried.
    Hygroscopicity might influence tablet properties upon
   storage.
4. Possess good technical properties:
   The primary function of the diluents is not that of improving
   powder flow and compactability. However, it is desirable that a
   diluent does not worsen powder flow and compactibility.
   In the contrary, when possible a diluent should improve powder
   flow and compactibility.
5. Have an acceptable taste
   In the case of uncoated tablets, the tablets will be in contact
   with the taste buds in the mouth.
   Therefore, as the diluent is often an excipient present in large
   amount in the tablets, it should have an acceptable taste.
   The taste of the diluent is extremely important in the case of
   lozenges, sublingual, chewable and buccal tablets.
6. Be of good biopharmaceutical properties
   Generally water-soluble and/or hydrophilic, so not to interfere with
   the immediate release of the drug

Question 43

Diluents used for direct compression vs wet granulation

Answer 43

The main difference between wet granulation diluents and
direct compression diluents is the particle size:
1. Diluents used in direct compression must be of free flowing
grade, therefore they have larger particle size.
2. Diluents used in wet granulation have smaller particle size
→There is no need for a free-flowing diluent powder in this
case, as the size enlargement provided by the granulation
will transform the powder into free-flowing granules.

Question 44

what are the advantages and disadvantages of lactose

Answer 44

Advantages:
 Lactose has a pleasant taste,
 It rapidly dissolves in water,
 It absorbs very little moisture
 Lactose has fair compressibility:
 Crystalline lactose undergoes fragmentation
 Amorphous lactose undergoes plastic deformation

Disadvantages:
 It is somewhat expensive
 It has poor flow characteristics.

Question 45

what is fast-flow lactose

Answer 45

 A particular grade of lactose, expensive, but with better flow
and compression properties than common grades of lactose.
 Used for direct compression, where flow and compression
properties of the diluents are crucial.
 Obtained by spray-drying of lactose solution: spherical and
hollow particles of amorphous lactose are produced, resulting
in:
 Improved flow
 Improved compaction properties

Question 46

what is MMC

Answer 46

nt. Several grades are available
both for direct compression and granulation.
MCC has disintegrating properties (also act as a
disintegrant)
MCC requires less lubricant in the formulation than other
diluents.
MCC has very good flow (coarser grades in particular)
MCC has excellent compaction properties (excellent dry
binder: it undergoes plastic deformation).
It is a good “all in 1” excipient.

Question 47

what is dicalcium phosphate

Answer 47

This diluent is used extensively.
It is insoluble in water, yet it is hydrophilic.
Mainly used for granulation.
It absorbs even less moisture than lactose and is therefore
used with hygroscopic drugs.
Slightly alkaline, incompatible with drugs sensitive to alkaline
conditions.

Question 48

what is mannitol

Answer 48

This sugar can be used for buccal, lozenges and chewable
tablets, as it has a pleasant taste.
Since it has a negative heat of solution*, it imparts a
pleasant taste and a cooling sensation when dissolved.
This diluent is expensive.
* more energy is required to break up the solid crystal than is
released in forming the solution

Question 49

what is dextrose and sucrose

Answer 49

Dextrose based granules are very soft and not very white. In
addition, dextrose absorbs moisture limiting its applicability in
cases of moisture sensitive drugs.
Sucrose is very hygroscopic and goes sticky on exposure to
moisture. Its pleasant taste makes it especially useful in lozenges

Question 50

what are binders

Answer 50

Also called adhesives or binding agents.
As a general term, they can be considered excipients that
ensure the formation of granules and tablets of good
mechanical strength. So they are like glue with adhesive
property.
Binders can be added to the powder in different ways,
depending on the type of process (direct compression, dry
granulation of wet granulation).

Question 51

what is the usage of binders in wet and dry granulation

Answer 51

In wet granulation:
The binder can be dissolved in the liquid used for wet
granulation, forming a solution. This binder is often refered to
as binder liquid. This is the most common situation.
Alternatively, before granulation, the binder can be added
as powder to the powder mixture of drug and excipients.
During the wet massing, the binder might dissolve in the
granulation liquid.
In both cases, the binder will provide strength to the
granules and later to the tablets.

In dry granulation:
The binder is mixed as powder before the dry granulation
(i.e. dry binder)
In direct compression:
The binder is mixed as powder before compression (i.e. dry
binder)

Question 52

name sime binders

Answer 52

Commonly used binders to form binder (granulation) liquid :
1. Polyvinyl Pyrrolidone (PVP)
2. Hydroxypropyl methylcellulose (HPMC)
Commonly used dry binders:
1. MCC
2. Cross-linked Polyvinyl Pyrrolidone

Question 53

what are disintegrats

Answer 53

These are agents that are added to tablets to promote
breakup of the tablets when placed in an aqueous
environment (i.e. the gastric fluids after tablet ingestion).
They comprise of a group of materials which on contact with
water swell, hydrate and produce disruptive change within a
tablet.
Hence, disintegrants will increase the rate of drug dissolution
and release from the dosage form

Question 54

when to mix disintegrates

Answer 54

In granulation the disintegrant can be mixed:
1. Either with the other powders before granulation and thus
incorporated within the granules (intragranular addition)
2. or the disintegrant can be added to the granules after
granulation, just before tableting (extragranular addition)
3. In some cases the disintegrant can be added both
intragranularly and extragranularly.

Question 55

what are the two types of disintegrates

Answer 55

1. Disintegrants that will rupture the tablet: these disintegrants
   absorb large amount of water that induce swelling of the
   tablet, resulting in rupture (i.e. burst open) of the tablet.
2. Disintegrants that promote water uptake: they facilitate
   wetting of the solid and the penetration of water into the
   pores of the tablets.

Question 56

give examples on disintegrants

Answer 56

1. The diluent MCC has very good disintegration properties.
2. Natural starch is used as common disintegrant.
3. Chemically modified starch (i.e. sodium starch glycolate)and
   chemically modified cellulose (i.e. crosscarmellose sodium)
   types with excellent swelling properties can be also used.
   These are defined as super disintegrants, as they are effective
   at lower concentration compared to conventional
   disintegrants.

Question 57

what are lubricants

Answer 57

These are agents that are used to prevent the adherence of
granules to the punch faces (such lubricants are referred to as
anti-adherent) and dies.
They also assure a smooth ejection of the tablet from the die.
How lubricants work:
Lubricants are agents that coat granules or particles of the
formulation. This coat remains more or less intact upon
compression (lubricants must be of very small particle size).
Such coating reduces the friction between tablets and die
walls thus facilitates ejection
Lubricants minimize abrasive wear of the punches and dies, by
reducing the friction between the powders/granules and
punches and dies.
Many lubricants can also improve the flow properties of
powders and granules (such lubricants also work as glidants

Question 58

what are Stearic acid and stearic acid salts (Mg, Ca)

Answer 58

Magnesium stearate is the most commonly used lubricant.
These lubricants are hydrophobic materials.
They are used in very small particle size (generally around
50µm).
They are normally used at low concentration (<1% by weight)
Stearates can cause important undesirable changes in tablets:
1. They can reduce tablet strength
2. They can reduce tablet disintegration and dissolution (→
because they create an hydrophobic coating on the surface of
drug and excipients particles).

The more the lubricant, the more evident are both these
problems:
→for this reason the amount of lubricant should be kept at the
minimum concentration possible
→ another possible option is to switch from the hydrophobic
lubricants to more hydrophilic lubricants

Question 59

other lubricants

Answer 59

Talc 1-2% Insoluble but not hydrophobic, lubricant
and glidant, not as good as stearates

Polyethylene
glycol (PEG)
2-5% M.wt 4000-6000, soluble in water,
moderately effective

Sodium lauryl
sulfate (SLS)
0.5-5% Moderate lubricant with wetting properties,
often used with stearates to minimize their
bad impact on tablet dissolution and
disintegratio

Question 60

what are glidants

Answer 60

ingredients that improve the flow properties of the
granulation from the hopper into feed frame, and ultimately
into the die cavity.
Glidant activity is attained by granule coating which dissipates
electrostatic charge, minimizes Van der Waals forces and
surface roughness. All of which reduce cohesiveness between
particles and hence improve flowability.
Good flowability ensures uniform die filling and hence minimum
variation in weights of tablets.

Question 61

give examples on glidants

Answer 61

Since lubricants can coat granules (or large particles) they can
serve as glidants.
Lubricants used as glidants are Mg stearate and Talc:
talc is poor lubricant, but efficient glidant. Traditionally talc
has been used as glidant in concentration of 1-2%.
Today, the most commonly used glidant is colloidal silicon
dioxide.
The effectiveness of these glidants is in the order of
Colloidal silica > Mg stearate > Talc

Question 62

what are the problems that happen during tableting

Answer 62

1. High weight and dose variation of the tablets
2. Low mechanical strength of the tablets
3. Capping and lamination
4. Picking and sticking of material to punches and die walls
5. Mottling

Question 63

what causes high weight and dose variation

Answer 63

High weight variation between tablets (i.e. non-uniformity of
weight) is generally due to bad flow. Solutions to this problem
have been previously discussed (in slide 18-19 of this Chapter
and in the flow Chapter).
High dose variation can depend directly on high weight
variations (and therefore on poor powder flow) or can be
caused by segregation of powder mixes (discussed in the Flow
and Mixing Chapters).
Overall good powder mixing and flow minimize the problem of
high weight and dose variations between tablets.

Question 64

what is capping and lamination

Answer 64

Capping refers to partial or complete separation of the bottom or
top crowns of a tablet from the main body of the tablet.
Lamination refers to tablets that split or crack on the sides causing
the separation of the tablet into two or more distinct layers.
Capping and lamination phenomena result when the particles
fail to bond under pressure.
They may happen during compression, immediately after
compression, hours or even days later.

Question 65

what are the causes of capping and lamination

Answer 65

I. Air entrapment
II. Deformational properties of the formulation
III. Over drying of granules
IV. Over-lubrication of powder or granulation mix
V. Punches fitting too closely to the die
VI. Tool wearing

Question 66

what leads to air entrapment

Answer 66

I.
Compression time (slow compression time is best to minimize air
entrapment)
II. Punches shape (flat shape are best to minimize air entrapment)
III. Presence of excessive fines (remember from flow chapter: bulk of fine
powders being cohesive tend to contain large and numerous air
voids)

Capping due to entrapped air is encountered less frequently on a
rotary than on a single punch machine because in the former
(rotary), the more gradual compression allows air time to escape.

Question 67

what leads to the Deformational properties of the formulation

Answer 67

During compaction particles undergo deformation, which can be relieved
by elastic recovery when the punch pressure is removed (stress
relaxation). Excessive stress relaxation can lead to capping and
lamination.
Materials with high tendency to elastic deformation upon compression,
often result in capping and lamination.
Moreover, excessive compression pressure applied during compression
can lead to excessive elastic recovery → capping and lamination

Question 68

what leads to tool wearing

Answer 68

 Tool wearing may develop over use and may lead to capping or
lamination.
 Die wearing can be caused by abrasive materials, sticking and
excessive high compression forces.
 Dies develop a wear ring in the area of compression (Ringed die)
 As the ring develops and enlarges, the tablets that are compressed
into the rings would have a diameter that is too large to pass easily
through the narrower portion of the die above the ring.
 Thus, upon ejection, this constriction causes the tablet to cap or
laminate

Question 69

what are picking and sticking

Answer 69

Picking: The removal of the surface material of tablet by
sticking to punches.
Sticking: The adhesion of tablet material to the die walls: this
adherence of particles to die wall cause difficult ejection.
 Such sticking may wear the die.
 In addition, sticking to the die wall will not allow the lower
punch to freely move inside the die upon ejection, which can
place stresses on the cam tracks and punch heads leading to
their damage.

Question 70

what causes picking and sticking

Answer 70

I. Low lubricant level or poor lubricant activity
II. High moisture level
III. Low melting ingredients
IV. Worn tooling
V. Dirty or unpolished die and/or punches

Question 71

how can we lower picking and sticking

Answer 71

I. Add/change a lubricant
II. Increase the binder, so particles are more cohesive to each
other and less adhesive to the die or punches.
III. Decrease the moisture content of the granules
IV. Clean the punch faces with 5% light mineral oil
V. Polish punch surface

Question 72

what is mottling

Answer 72

It is an unequal distribution of the color on the surface of the
tablet
Causes and Treatment:
The drug may have a different color from the excipients
used. The treatment is to use a dye that masks the change.
Migration of the dye during drying of the granulation. To
overcome this difficulty, the formulator may change the
solvent system or grind to smaller particle size.
Coating

Question 73

what test do we do to test the quality of the tablets

Answer 73

– uniformity of diameter
– uniformity of weight*
– uniformity of content*
– Disintegration*
– Dissolution*
– Hardness*
– Friability*