Nahla Barakat, PhD
King Saud University
Dept. of Pharmaceutics
• Tablets are oral solid unit dosage form of medicaments with or without
suitable diluents and prepared either by molding or compression. They are
solid, flat or biconvex disc in shape.
•They vary greatly in shape, size and weight which depend upon amount of
medicament used and mode of administration.
•They also vary in hardness, thickness, disintegration and dissolution
characteristics and in other aspects depending upon their intended use and
method of manufacture
•They are used for local & systemic effect.
• Usually used for oral administration
Tablets are popular due to:
1. A convenient and safe way of drug administration.
2. Compared to liquid dosage form they are more physically &
3. Enables more accurate dosing , easy to use, handle by the patient
4. Can be prepared in different ways according to their use.
5. Tablets are provides a sealed covering which protects the tablets from
atmospheric conditions like air, moisture and light etc.
6. The manufacturing cost of tablets is low as compared to other dosage
7. The unpleasant taste and odor of medicament(s) can be easily masked by
8.Tablets provide administration of even minute dose of drug in an accurate
9. Tablets are formulated as a special release of products such as enteric or
delayed release products.
Disadvantages of tablet:
1. It’s not suitable for poorly water-soluble or poorly
absorbable drugs, less bioavailability.
2. Enhances local irritant effect of some drugs or cause harm
to the gastrointestinal mucosa.
3.Some drugs resist compression into dense compacts.
4. Hygroscopic drugs are not suitable candidate for compressed
5. Drugs having bitter taste and unpleasant odor requires special
treatment like coating or encapsulation which may increase their
6. Drugs that are sensitive to oxygen or may also require special
General properties of Tablet dosage forms:
1.A tablet should have elegant product identity while free of
defects like chips, cracks, discoloration, and contamination.
2.Should have sufficient strength to withstand mechanical shock
during its production packaging, shipping and dispensing.
3.Should have the chemical and physical stability to maintain its
physical attributes over time
4.The tablet must be able to release the medicinal agents in a
predictable and reproducible manner.
5.Must have a chemical stability over time so as not to follow
alteration of the medicinal agents.
6.The appearance of the tablet should be elegant and its weight,
size and appearance should be consistent
Tablet Ingredients (excipients)
• Excipients are chosen in tablet formulation to perform a variety of
i) For providing essential manufacturing technology functions (binders,
glidants, lubricants may be added),
ii)For enhancing patient acceptance (flavors, colourants may be added),
iii)For providing aid in product identification (colourants may be added),
iv)For Optimizing or modifying drug release (disintegrants, hydrophilic
polymers, wetting agents, biodegradable polymers may be added),
v)For enhancing stability (antioxidant, UV absorbers may be adde
1- Filler or diluent
use: to make required bulk of the tablet .
to provide better tablet properties such as to improve cohesion,
to permit use of direct compression manufacturing
to improve flow
• Most common fillers in tablets:
1. Lactose, sucrose, mannitol; frequently used, water soluble,
improves tablet disintegration.
2. Dicalcium phosphate dihydrate, insoluble in water,
disintegrating agent is a must.
3. Mannitol, dextrose, sucrose, 4. Lactose-anhydrous and spray
dried lactose 5. Directly compressed starch-Sta Rx 1500
6. Hydrolyzed starch-Emdex and Celutab
7. Microcrystalline cellulose-Avicel (PH 101, 102)
Requirements for a good filler:
1. Chemically inert, biocompatible, cheap.
3. Good biopharmaceutical properties. (water soluble or hydrophilic).
4. Good technical properties (compactability )
5. Have an acceptable taste.
6. They must be free from all microbial contamination.
7. They do not alter the bioavailability of drug.
8. They must be color compatible.
9. They must be non toxic
10. They must be commercially available in acceptable grade
11. They must be physically, chemically stable in combination with the
Role: to ensure that the tablet, when in contact with a liquid, breaks up
into small fragments, which promotes rapid drug dissolution.
Mode of action:
1. Facilitate water uptake into the pores of tablet,
e.g. surface active agents
2.facilitate rupture of tablet by swelling during water sorption,
e.g. Sodium –starch glycolate, Crosscarmelose- cross linked cellulose;
modified cellulose, Ac-Di-Sol
3. Release of gases to disrupt the tablet structure, normally carbon dioxide,
in contact with water. e.g. effervescent tablets.
The Method of Disintegrant Addition:
1. Mixed with other ingredients prior to granulation & thus
incorporated within the granules (intragranular addition).
2. Mixed with the dry granules before the complete powder mix
is compacted (extragranular addition).
3. incorporated as both an intragranular and an extragranular
Commonly Used Disintegrants:
1. Starch: - conc. Up to 5-20% of tablet weight
- Swell in contact with water
2. Super disintegrants (e.g. crrosecarmelose, sodium starch
glycolate (Explotab), Crosspovidone-cross linked povidone)
Swells up to ten fold within 30 seconds when contact water.
3. Clays: bentonite, Veegum 10 % level in coloured tablet only
3- Binder and adhesive
Role: Ensure that granules and tablets can be formed
with the required mechanical strength ( glue that holds
powders together to form granules ).
- In dry powder form
- In solution
starch paste 5-25%
gelatin solution 10-20%,
gum acacia, tragacanth, 10-25%
Liquid glucose 50%,
Polyvinylpyrrolidone 2% (PVP), PEG
prevent adherence of granule/powder to die wall and
promote smooth ejection from the die after compaction,
reduce inter particle friction and
improve the rate of flow of the tablet granulation
• Mechanisms of Action :
1. Fluid lubrication.
2. Boundary lubrication.
Disadvantages of lubricants
1. Lubricants tend to be hydrophobic, so their levels (typically
0.3 – 2%) need to be optimized:
– Under-lubricated blends tend to flow poorly and show
compression sticking problems
– Over-lubricated blends can adversely affect tablet hardness
and dissolution rate, as well as tablet strength.
– To overcome these problems;
- Optimum conc. < 2%
- Addition of SAA (surfactant)
Commonly used Lubricants
A. Water- insoluble (Fatty acids-based) lubricant
• Magnesium Stearate
• Calcium Stearate
• Stearic Acid, stearic acid salt
• Silica derivative- colloidal silica such as Cab-O-Sil,
Aerosil in 0.25-3% conc.
• liquid Paraffin, propylene glycol (PG)
B. water-soluble lubricant
- PEG 6000; less effective
- Magnesium lauryl sulfate; good lubrication and surface
Role: Improve flowability of the powder
They are added during direct compaction and to granulation before
tabletting ( they reduce interparticulate friction).
• Common Glidants:
1. Talc (at concentration 1-2 %).
2. Colloidal silica (0.2 %).
3. Corn Starch 5-10%
Role: Reduce adhesion between the powder and
the punch faces
thus prevent particles sticking to the punches
• Many lubricants, such as magnesium stearate, have
also antiadherent properties.
Also talc and cornstarch, colloidal silica, can act as
Adsorbents are the agents that can retain large quantities of
Therefore liquids like Vitamin E can be incorporated into tablets
by addition of adsorbents .
Most commonly used adsorbents in pharmaceuticals are
anhydrous calcium phosphate, starch, magnesium carbonate,
bentonite, kaolin, magnesium silicate, magnesium oxide and
Generally the liquid to be adsorbed is first mixed with the
adsorbent prior to incorporation into the formulation.
Silicon dioxide when added can play as both glidant and an
adsorbent role in the formula.
Use: give the tablet a more pleasant taste or
to mask an unpleasant one. (Chewable tablet)
• Flavouring agents are often thermolabile and so
cannot be added prior to an operation involving heat.
• They are often mixed with the granules as an
Ex: Flavour oil
Uses: It is added to tablets to aid identification,
Improve patient compliance.
Mask of off color drug
Production of more elegant product.
All coloring agents must be approved and certified by FDA.
Two forms of colors are used in tablet preparation – FD &C and
D & C dyes.
These dyes are applied as solution in the granulating agent or
Lake form of these dyes.
Lakes are dyes absorbed on hydrous oxide and employed as dry
Yellow 6- FD & C sunset yellow
yellow 5- FD & C Tartrazine
green 3- FD & C Fast Green
blue 1- FD & C Brilliant Blue
blue 2 – FD & C Indigotine
red 3- FD & C Erythrosine FD & C
red 22 – FD & C Eosin Y
It is added during coating.
• It can also be added prior to compaction. ( can be added as
an insoluble powder or dissolved in the granulation liquid
They are used in chewable tablet to exclude or limit the use of
sugar in the tablets.
e.g. Mannitol, lactose, sucrose, Dextrose 72% as sweet as
Saccharin, 500 times sweeter than sucrose.
Disadvantage: has a bitter after taste and carcinogenic.
Aspartame, largely replace saccharin., 180 times sweeter than
Disadvantage: lack of stability in the presence of moisture.
Buffers are added to maintain a required pH since a change in
pH may cause significant alteration in stability.
Most commonly used buffering agent in tablet formulation
includes sodium bicarbonate, calcium carbonate, and sodium
Antioxidants are added in tablet formulation: to protect drug from
Chelators may also act as antioxidant.
Most commonly used antioxidants include ascorbic acid and their esters
,alpha-tocopherol , ethylene diamine tetra acetic acid , sodium
metabisulfite , sodium bisulfite , Butylated Hydroxy Toluene (BHT) ,
Butylated Hydroxy Anisole (BHA) , citric acid , and tartaric acid .
13. Chelating agents
tend to form complexes with trace amount of heavy metal ions
inactivating their catalytic activity in the oxidation of medicaments.
Ethylenediamine tetracetic acid and its salts, Dihydroxy Ethyl Glycine,
Citric Acid and Tartaric Acid are most commonly used chelators.
14. Dissolution Enhancers
They are the agents that alter the molecular forces between ingredients to
enhance the dissolution of solute in the solvent.
Fructose, Povidone, Surfactants are used as dissolution enhancer.
15. Dissolution Retardants
Dissolution Retardants are incorporated into tablet formulation only when
controlled release of drug is required.
Waxy materials like stearic acid and their esters can be used as
16. Wetting Agents
in tablet formulation aid water uptake and thereby enhancing
disintegration and assisting in drug dissolution.
Incorporation of anionic surfactant like Sodium Lauryl Sulphate (SLS)
is known to enhance the dissolution.
SLS improves permeation of drug through biological membrane since it
destroys the path through which drug has to pass and thus minimizing the
path length for the drug to travel.
Wetting agents are mainly added when hydrophobic drug is to be
formulated into tablet.
SLS, Sodium diisobutyl sulfosuccinate are used as wetting agent in
1. High Purity
API has to be in pure form otherwise impurities can catalyze series of
e.g. in case of hydrocortisone impurity of cupric ion causes oxidation of
ketone functional group.
API should meet specifications given in the respective Pharmacopoeia.
2. High stability
The API should be stable against photolysis, oxidation, hydrolysis, etc. to
keep the formulation a simple one.
Sensitive particles require careful handling during manufacturing.
3. Good compatibility with excipients
There should not be any kind of interaction between excipient and API.
Excipients have to be inert in nature.
However there are some reported examples of API-excipient interactions
like Lisinopril reacts with lactose and undergoes browning reaction leading
to darkening on storage.
So, avoid the use of lactose and use other fillers for API containing
primary amine. To ascertain drug and excipient interaction, 1:1 mixture is
prepared and stored under accelerated/ICH conditions.
The amount of drug degraded shall be determined to select the most
4. Optimum bulk powder properties
Bulk powder properties have to be optimum to:
i) Prevent segregation.
ii) Have optimum size tablet particularly for low potency-low density API.
iii) Have good flow.
5. Optimum and Uniform particle size-particle size distribution
API should have uniform particle size and close particle size distribution
because it has pronounce effect on uniformity of content, uniformity of weight,
disintegration time, granule friability, drying rate kinetics of wet granulation,
flowability, compressibility, stability, dissolution, bioavailability, etc.
• The flow and compression characteristics are important from the viewpoint of
• Strong tablets are obtained if fine particles are used due to increase in surface
area and surface energy.
6. Spherical shape
Spherical shaped particles exhibit good flow as compared to needle shaped
• Particles with irregular shape may exhibit hindered flow due to interlocking
• This point is very important since it is directly related with weight of tablet
7. Good flowability
Flow is important for having uniformity of weight and uniformity of drug
It can be measured using angle of repose, Carr’s index and Hausner ratio.
The methods used to improve flow are summarized below
i) Addition of glidants
ii) Addition of fines: Addition of fines up to certain extent improves flow.
This is because of filling of void space and decrease in surface roughness.
iii) By wet granulation: Wet granulation gives regular sphere shaped granules
and removes static charge, thus, flow property improved.
8. Optimum moisture content
Moisture content has to be optimum because of the following reasons:
i) Total lack of moisture results into brittle tablet.
ii) Moisture affects flow, which in turn affects uniformity of content.
iii) High amount of moisture gives stickiness, which will affect compaction.
iv) Picking/sticking may be observed.
Moisture content can be controlled by:
i) Use of anhydrous salts.
ii) Use of non-aqueous solvent.
iii) Optimum drying time.
iv) Addition of finely powdered adsorbent like magnesium oxide
9. Absence of static charge on surface
It is important because of the following reasons:
i) Affects uniformity of dose and weight variation (flow worsen if
attractive forces generated).
ii) During mixing it may cause segregation and lead to non-uniformity
of content if API and excipients are charged.
iii) Charged API may adhere to feed frame and result into serious
damage to tablet equipment.
In order to remove charge certain treatments can be given like
addition of diluents or lubricant,
surface coating with help of colloidal silica, etc.
10. Good organoleptic properties
Many API are unpalatable and unattractive in their natural form.
In such cases, tablet formulation require certain care.
API has to be checked for colour and taste.
Ideally API should be colourless. For coloured API, the following steps
shall be considered:
i) Select appropriate excipient to avoid mottling.
ii) Incorporate API in smallest particle size.
iii) Incorporate colour in dry form along with binder and activate mixture
by addition of water or other activator.
iv) Coating can be applied to conceal non-uniform colour (sugar coated
It is very important for tablets because they come in contact with
Ideally API should have no taste.
Sometimes it might have unpleasant taste like bitter e.g.
Chloramphenicol, Clindamycin, etc. The following taste masking
options can be tried:
i) Use of prodrug to decrease API solubility in saliva or to reduce
affinity for taste receptor e.g. Chloramphenicol Palmitate.
ii) Sugar coating or film coating.
iii) Addition of sweeteners like mannitol in case of fast dissolving
tablet or chewable tablet.
iv) Use of drug-ion exchange adsorbent in formulation.
v) Drug β-cyclodextrin complex may exhibit good taste profile and
good compressibility as well.
TABLE.1. EXCIPIENT WITH THEIR FUNCTIONS IN TABLET FORMULATION
Diluent Diluents make the required bulk of the tablet when
the drug dosage itself is inadequate to produce
tablets of adequate weight and size
Binder Binders are added to tablet formulations to add
cohesiveness to powders, thus providing the
necessary bonding to form granules, which under
compaction form a cohesive mass or a compact
which is referred to as a tablet.
Disintegrants A disintegrant is added to most tablet formulations
to facilitate a breakup or disintegration of the tablet
when placed in an aqueous environment.
Lubricant Lubricants are intended to reduce the friction
during tablet formation in a die and also during
ejection from die cavity.
Antiadherants Antiadherents are added to reduce sticking or
adhesion of any of the tablet granulation or
powder to the faces of the punches or to the die
Glidants Glidants are intended to promote the flow of
tablet granulation or powder mixture from
hopper to the die cavity by reducing friction
between the particles.
Wetting agent Wetting agents are added to tablet formulation to aid water
uptake during disintegration and assist drug dissolution.
Dissolution Dissolution retardants as the name suggest, retards the
retardant dissolution of active pharmaceutical ingredient(s).
Dissolution Dissolution enhancers as the name suggest, enhance the
enhancer dissolution rate of active pharmaceutical ingredient(s).
buffers Buffers are added to provide suitable micro environmental pH
to get improved stability and / or bioavailability.
Adsorbents Adsorbents are capable of retaining large quantities of liquids
without becoming wet; this property of absorbent allows
many oils, fluid extracts and eutectic melts to be incorporated
Antioxidants Antioxidants are added to maintain product stability, they
act by being preferentially oxidized and gradually
c.onsumed over shelf life of the product
Chelating Chelating agents are added to protect against autoxidation;
agents they act by forming complexes with the heavy metal ions
which are often required to initiate oxidative reactions.
Colours Colours are added to tablet formulation for following
purposes: to disguise off colour drugs, product
identification and for production of more elegant product.
Flavours Flavours are added to tablet formulation in order to make
them palatable enough in case of chewable tablet by
improving the taste.
1- Disintegrating tablets
• Most common type is intended to be swallowed and releases the drug in a
relatively short time after disintegration and dissolution thus fast & complete
drug release in vivo (conventional or plain tablets).
• A disintegrating tablets include the following types of excipients: filler (if the
dose of drug is low), disintegrant, binder, glidant, lubricant and antiadherent.
Steps of drug release from disintegrating tablets
Conventional tablet may be single layer or multilayer.
Multilayer tablets are prepared by repeated compression of
powders and are made primarily to separate incompatible drugs
from each other.
Tablet, multilayer: This is a solid dosage form that contains
medicinal substances that have been compressed to form a
multiple-layered tablet or a tablet-within-a-tablet (the inner
tablet being the core and the outer portion being the shell).
2- Chewable tablets
• They are chewed so mechanically disintegrated in the mouth.
• The drug is not dissolved in the mouth but swallowed and dissolves in the
stomach or intestine.,
• and it does not leave a bitter or unpleasant after-taste.
Advantages of chewable tablets:
1. Quick and complete disintegration of the tablet - and hence obtain a rapid
drug effect after swallowing and dissolution. e.g. antacid tablets.
2. Facilitate the intake of the tablet for elderly and children who have difficulty
in swallowing; e.g. vitamin tablets.
3. Can be taken when water is not available.
Mannitol is normally used as a base due to low hygroscopy and more
importantly, it gives pleasant, cooling sensation.
They are similar in composition to conventional tablets except that a disintegrant
is normally not included.
• They are tablets that dissolve slowly in the mouth and so
release the drug dissolved in the saliva.
• They can thus be described as slow-release tablets for
local drug treatment.
Use of lozenges:
Local medication in the mouth or throat in common cold, to
treat cough by:
antitussive agents or astringents.
Lozenges are usually contain:
1.They are similar in composition to conventional tablets.
2. Disintegrants are not included in Lozenges tablets.
3. Colour, sweetener and flavour.
4. High concentration of Fillers which are mainly sugars,
such as glucose, sorbitol or mannitol.
5. Other additives (binder and filler) must have pleasant taste.
6. Common binder used in compressed lozenges is gelatin
7. The tablet generally contains sucrose or lactose and gelatin
solution to impart smooth taste
Hard candy lozenges, e.g. Halls®, may be made by molding into
a hard candy lozenges using candy making machine,
For thermostable drugs, warm, highly conc. flavored syrup is
used as a base and the lozenges are formed by molding and
4- Sublingual and buccal tablets
Used for drug release in the mouth followed by systemic
uptake of the drug.
• Rapid systemic drug effect can thus be obtained without first-
pass liver metabolism.
• Sublingual tablets are placed under the tongue and buccal
tablets are placed in the side of the cheek.
• They are often small and porous, to facilitate fast
disintegration and drug release.
Sublingual tablets are placed under the tongue,
Nitroglycerin sublingual tablet; it exerts its action within two
minutes for rapid relief of "Angina pectoris" attack, because
the sublingual area is rich in blood supply.
• Also other cardiovascular drugs, barbiturates, and vitamins
are prepared as sublingual tablet dosage form
Buccal tablets are placed in the side of the check for absorption through oral
• N.B. Buccal tablets may be also prepared for their local application.
Buccal tablets are intended to be placed on the gum or in the cheek to allow
the drug absorbed.
• Because the medicine can be held for a longer period of time on the gum,
medicines which need to be released at a slower rate can be given via this
• This route is used for anti-nausea drugs and nicotine replacement
5. Dispersible tablet
These tablets disintegrate either rapidly in water, to form a stabilized
suspension, or disperse instantaneously in the mouth to be swallowed without
the aid of water.
It’s preferred for pediatric patients who cannot swallow a solid dosage
form and the AP I is unstable if formulated in liquid formulation.
Also helpful for patients having prolonged illness who are prone to
nauseatic sensations if they have to swallow a tablet.
Faster onset of action as compared to standard compressed tablet.
The common examples of API formulated in this dosage form are analgesics
e.g., aspirin, ibuprofen, etc.
6- Melts tablet
Melt tablets are placed on the tongue and are designed to
dissolve directly in the mouth's saliva.
The contents are then swallowed with saliva and
consequently water does not have to be administered with
This is particularly useful in patients who are at risk of
aspiration and therefore unable to swallow tablets with water
7- Oro-dispersible tablets
Oro-dispersible tablets are similar to melts and are designed to
disperse in the mouth and to be washed down with saliva.
Like sub-lingual, buccal and melts, oro-dispersible products
require an adequate amount of saliva production
8- Vaginal tablets
Vaginal tablets are compressed tablets meant for insertion into vaginal
cavity and designed to undergo slow dissolution and drug release in the
Sometimes vaginal suppositories or pessaries are prepared by compression
which are known as vaginal tablets.
These are usually ovoid or almond in shape to facilitate the retention in
It is used to release antibacterial agents, astringents and antiseptics to treat
vaginal infection or possibly to release steroids for systemic absorption.
Soluble additives are used for the preparation of these tablets. These are
often formulated with buffering agent to provide favorable pH to stimulate
the action of the given medicament(s).
Tablets used to prepare solution
1. Soluble tablet
• Soluble tablets are uncoated or film- coated tablets.
• Tablets are solids of uniform shape and dimensions, usually
circular, with either flat or convex faces.
• Water soluble tablets are intended for application after
dissolution in water and contain an active ingredient should be
totally soluble in water at used concentrations.
•All the excipients used to formulate these tablets are required
to be completely soluble in water
2- Effervescent tablets
Effervescent tablets are dropped into a glass of water
before administration, during which carbon dioxide
CO2 facilitates tablet disintegration and drug
dissolution; the dissolution of the tablet should be complete
within a few minutes.
Advantages of effervescent tablets:
1. Rapid drug action, e.g. analgesic drugs .
2. Facilitate the intake of the drug, e.g. vitamins.
3. Fast drug bioavailability
Effervescent tablets are usually contained:
Carbonate or bicarbonate and a weak acid such as citric or tartaric.
Flavor and a colourant
A water-soluble lubricant is preferable
Effervescent tablets should be:
protected from moisture, so that a special package is
each tablet is completely covered with aluminum
foil and kept in a water-proof container, often
including a desiccant.
Effervescent tablets may be packed in blister packs.
3. Hypodermic tablet
These tablets contain one or more readily water soluble
ingredients and are intended to be added in water for injection
of sterile water to form a clear solution which is to be injected
They were widely used by rural physician due to its
One bottle of sterile water was carried by the doctor to
prepare many types of injectables.
It can be used for medicaments whose stability in water is
ORAL TABLETS FOR Standard compressed
INGESTION These tablets tablets
are meant to be swallowed Multiple compressed tablets
intact along with a sufficient I. Compression coated
quantity of potable water. tablet
Exception is chewable II. Layered tablet
tablet. Over 90% of the
tablets manufactured today Modified Release tablet
are ingested orally. This Delayed action tablet
shows that this class of Targeted tablet
formulation is the most I. Floating tablet
popular world wide and the II. Colon targeting tablet
major attention of the Chewable tablet
researcher is towards this Dispersible tablet
TABLETS USED IN THE Lozenges and troches
ORAL CAVITY The tablets Sublingual tablet
under this group are aimed Buccal tablet
release API in oral cavity or to Mouth dissolved tablet
provide local action in this
region. The tablets under this
category avoids first-pass
metabolism, decomposition in
gastric environment, nauseatic
sensations and gives rapid onset
of action. The tablets formulated
for this region are designed to fit
in proper region of oral cavity.
TABLETS ADMINISTERED Vaginal tablet
BY OTHER ROUTES These Implants
tablets are administered by
other route except for the oral
cavity and so the drugs are
avoided from passing through
gastro intestinal tract.
These tablets may be inserted
into other body cavities or
directly placed below the skin to
be absorbed into systemic
circulation from the site of
TABLETS USED TO PREPARE Effervescent tablet
SOLUTION Hypodermic tablet
The tablets under this category Soluble tablet
are required to be dissolved first
in water or other solvents before
administration or application.
This solution may be for
ingestion or parenteral
application or for topical use
depending upon type of