2. DrugDrug
Drug may be defined as an
agent or substance, intended
for use in the diagnosis,
mitigation, treatment, cure or
prevention of disease in
human beings or animals.
Drugs are rarely administered
in their original or crude
forms. They are administered
in different dosage forms by
converting them into suitable
formulations.
Crude Drugs
3. Dosage FormsDosage Forms
Dosage forms are the carrier through which
drug molecules are delivered to sites of
action within the body.
Every dosage forms is a combination of the
drug and different kinds of non – drug
components called as Excipients or additives.
The additives are used to give a particular
shape to the formulation, to increase
stability, palatability & more elegance to
preparations.
4. Need For Dosage FormsNeed For Dosage Forms
Accurate dose.
Protection e.g. coated tablets, sealed ampules.
Protection from gastric juice, e.g. enteric
coated tablets.
Masking unpleasant taste and odour.
Provide drugs within body tissues, e.g.
injection
Sustained release medication.
Facilation of Insertion of drugs into body
5. Provide optimum drug action through
inhalation therapy.
Provide drug action through topical
administration at local area of body. e.g.
creams, ointment, emulsion, lotions etc.
Use of desired vehicle for insoluble drugs.
9. SOLID DOSAGE FORMS
Solid dosage forms one of the oldest dosage forms
and most of the solid dosage forms are available in
Unit dose.
Unit dose may be defined as a exact quantity of the
drug administered at once. e.g. Tablets, Capsule, pills,
cachets, powders etc.
When drugs are to be administered orally in dry state,
then tablets, capsules are most convenient dosage
forms.
Some solids are supplied in bulk (Means quantity
available in large). Bulk powders can be supplied as
Internal (Granules, Fine powders) as well as External
(Dusting Powders, Insufflations etc)
10. Dusting PowdersDusting Powders
Dusting powders are applied externally to skin, so
they should be applied in very fine state to avoid local
irritation. Hence dusting powders should be passed
through sieve no 80 to obtained fined powders.
Dusting powders are prepared by mixing of more than
one ingredients in which either starch, kaolin, or talc
are used in their formulation. Generally talc or kaolin
are used because they are inert in nature.
Dusting powders are used for antiseptic, astringent,
absorbent, antiperspirant etc.
Dusting powders are of two sub type they are as
I) Medical dusting powder
II) Surgical Dusting powders
11. Medical Dusting PowdersMedical Dusting Powders
Medical Dusting powders are used to
increase superficial condition of skin.
These are not applied on wounds, burns etc
Medical dusting powders must be free from
dangerous pathogenic micro- organism.
12. Surgical Dusting PowdersSurgical Dusting Powders
Surgical dusting powders are used in body
cavities and also on major wounds like as
burns etc.
They should be sterilized before use.
They are mainly used for their antiseptic,
absorbent action.
13. InsufflationsInsufflations
These are medicated dusting powders meant for
introduction into body cavities (nose, throat, ear,
vagina etc) with the help of an apparatus known as a
insufflator.
It sprays the powders (in a state of fine particles) on
site of application.
Now a days insufflations are also available in pressure
aerosols. This pressure aerosols are used for
administration of potent drug.
They are used in the treatment of ear, nose, throat
infections with antibiotics to produce local effect of
drugs.
14. SnuffsSnuffs
These are finely divided solid dosage
forms of medicaments which are inhaled
into nostrils.
They are mainly used for their antiseptic,
bronchodilator and decongestion action.
15. GranulesGranules
Granulation is the process in which primary
powder particles are made to adhere to form
larger multiparticle or large particles entities
called granules.
The bitter, nauseous, unpleasant powders can
not be given tablets, capsule due to bulk
quantity are required to be taken, as well as
they are not given in liquid dosage forms due to
their stability such powders are given in the
granules forms.
These powders are mixed with suitable
exicipent along with granulating agent, prepare
a coherent mass then dried & passed through
the sieve to obtained desired size of granules.
E.g. Effervescent granules
16. Effervescent GranulesEffervescent Granules
Effervescent granules are meant for internal use.
They contained medicaments mixed with citric acid,
tartaric acid & sodium bi carbonates, sometime
saccharin or sucrose may be added for sweetening
taste.
Before, administration desired quantity of granules are
dissolved in water, the acid & bicarbonate reacts with
each other to produce effervescence.
Effervescent granules are prepared by two methods,
namely as, I) Heat method, II) Wet method
17. Heat methodHeat method
A large porcelain or stainless steel evaporating dish is placed over
the boiling water bath.
The dish must be sufficiently hot (generally heating takes place for
1 – 5 min.) before transferring the powders into it, to ensure rapid
liberation of water of crystallization from citric acid.
If heating of the dish is delayed then the powder which is added to
it, will heat up slowly & liberated water of crystallization will also
be liberated simultaneously.
As a result, sufficient water will not be available to make a
coherent mass.
This coherent mass will pass through the sieve to obtained suitable
size of granules, dry it in oven at 600
c then packed in air tight
container.
18. Wet methodWet method
In this methods all the ingredients are mixed thoroughly
This powders mixture make moistened with non –
aqueous vehicle (e.g. alcohol), to prepare a coherent
mass which is then passed through sieve no 8 to
obtained suitable granules.
Then dried in oven at 600
c. The dried granules are again
passed through the sieve to break the lumps which may
be formed during drying.
The dried granules are packed in air tight container.
19. TabletsTablets
These are solid dosage forms of medicaments which are
prepared by moulding or by compression with or
without Excipients.
The tablets can be prepared by two methods namely as
I) Dry granulation
II) Wet Granulation
20. CapsuleCapsule
Capsules are solid unit dosage forms in which one or more
medicaments enclosed within a shell.
Capsules mainly divided in to two parts namely as –
I) Body (Longest part of capsule shell), II) Cap (Smallest part of
capsule shell)
The capsule are generally prepared by gelatin.
Depending on their formulation, two types of gelatin are used
namely as – I) Hard gelatin, II) Soft gelatin.
Body
Cap
21. PillsPills
These are small, rounded solid dosage forms
containing medicaments intended for oral use.
The medicaments are mixed with excipients to forms
a firms plastic mass.
The mass is rolled to uniform pill pipe, which cut into
numbers of uniform pills. The pills are spherical in
shape & produced by rolling them under wooden pill
rounder.
Sometimes pills are coated with varnish, gold leaf, etc
to improve finish, unpleasant taste & stability.
Now a days pills are outdated preparations because of
number of disadvantages such as -
22. Disintegration time of pill is uncertain means freshly prepared
pills are disintegrates readily rather than old dried pills.
It is difficult to prepare pills of uniform size & weight.
26. It may be defined as “A solution is a liquid-preparation that
contains one or more soluble chemical substances dissolved
in a specified solvent”
Liquid dosage forms are intended for External, Internal or
parenteral use.
The component of the solution which is present in a large
quantity is known as “SOLVENT” where as the component
present in small quantity is termed as “SOLUTE”
They mainly classified in to two category namely as –
I) Monophasic Liquid dosage forms.
II) Biphasic liquid dosage forms.
27. AdvantagesAdvantages
Immediately available for absorption.
Administration convenient, particularly for infants, psychotic
patients.
Easy to color, flavor & sweeten.
Liquids are easier to swallow than solids and are therefore
particularly acceptable for pediatric patient.
A solution is an homogeneous system and therefore the drug
will be uniformly distributed throughout the preparation.
Some drugs like aspirin, KCl can irritate gastric mucosa if
used orally as a solid dosage forms. But this effect can be
reduce by solution system.
28. DisadvantagesDisadvantages
Less stable in aqueous system. Incompatibility is faster in
solution than solid dosage form.
Patients have no accurate measuring device.
Accident breakage of container results in complete loss.
Solution often provide suitable media for the growth of micro
organisms.
The taste of a drug, which is often unpleasant, is always more
pronounced when in solution than in a solid form.
Bulky than tablets or capsule, so difficult to carry transport.
30. Monophasic liquid dosage forms are represent by true or
colloidal solution.
The component of the solution which is present in a large
quantity is known as “SOLVENT” where as the component
present in small quantity is termed as “SOLUTE”.
A solution is homogenous because the solute is an ionic or
molecular forms of subdivision.
In case of colloidal solutions, the solutes are present as
aggregates although they cannot be seen by necked eye or
ordinary microscope.
It is sub classified as –
I) Internal Use, II) External use
33. SyrupSyrup
It is a concentrated or saturated solutions of sucrose in
purified water.
The concentration of sucrose is 66.7% w/w & due to that it is
a viscous preparations.
The syrup which contains medical substance called as a
medicated syrup & those containing aromatic or flavored
substance known as a flavored syrup.
34. Importance of syrupImportance of syrup
It retards oxidation because its partly hydrolyzed into
reducing sugar.
It prevents decomposition of many vegetable substance
because its have high osmotic pressure which prevent the
growth of bacteria.
They are palatable due sweet taste.
35. ElixirsElixirs
It is clear, sweetened, aromatic,
hydroalcholic preparations meant
for oral use.
The medicated elixirs are generally
contained potent drug like as
antibiotics, antihistamine or sedative
, where as non – medicated elixirs
contained flavoured.
The composition of elixirs
contained mainly as ethyl alcohol
(active ingredients),water, glycerin
or propylene glycol, colouring agent,
flavouring agent & preservative.
36. LinctusesLinctuses
These are viscous liquid preparations
that’s are used for the treatment of
cough.
They contain medicaments which have
demulcent, sedative, expectorant action.
They are taken in small doses without
diluting with water to have prolonged
effect of medicines.
Simple syrup is used as a vehicle for most
of the linctuses.
Tolu syrup is preferred in certain cases
because of its aromatic odour & flavour.
Moreover it have a mild expectorant
action
37. DropsDrops
These are liquid preparations meant for oral
administration.
The oil soluble vitamins, such as vitamin A & D
concentrates in fish – liver oil are presented as drops
for administration.
Since these preparations contain potent medicaments,
the dose must be measured accurately
The following two methods are commonly used for this
purpose.
Use of a dropper which is accurately graduated in
fractions of a milliliters.
Use of a pre – calibrated dropper.
38.
39. LinimentsLiniments
Liniments are liquid or semi- liquid preparations
meant for external application to the skin.
They are usually applied to the skin with friction
& rubbing of the skin.
Are usually alcoholic and oily liquid preparations
(monophasic) or emulsion (biphasic).
Alcoholic liniments are used generally for their
rubefacient and counterirritant effects. Such
liniments penetrate the skin more readily than
do those with an oil base.
The oily liniments are milder in their action and
may function solely as protective coatings
Liniments should not be applied to skin that are
bruised or broken.
40. LotionsLotions
Are usually aqueous, alcoholic or
oily liquid preparations.
They are intended for external
application without friction or
rubbing to the affected area
Usually applied with the help of
some absorbent material such as
cotton wool or gauze.
It is generally used to provide
cooling, soothing and protective &
antiseptic action.
41. GarglesGargles
Gargles are aqueous solutions used for treating throat infection
(pharynx and nasopharynx part)
Supplied in concentrated forms with directions of dilution with warm
water before use
They are used into intimate contact with the mucous membrane of
throat for few seconds, before they are thrown out of the mouth.
They are used to relieve soreness in mild throat infection.
They are also used for their antiseptics, antibiotics and/or anesthetics
42. Mouth washMouth wash
These are aqueous solutions with
pleasant or acceptable taste & odour
These are used to make clean &
deodorise the buccal cavity or used
for oral hygiene and to treat
infections of the mouth.
They mainly contain antibacterial
agent, alcohol, glycerin, sweetening
agent, flavoring agent & colouring
agent.
43. Throat paintsThroat paints
Throat paints are viscous liquid
preparations used for mouth and
throat infections
Glycerin is commonly used as a
base because being viscous it
adheres to mucous membrane for
long period and it possess a sweet
taste.
44. SpraysSprays
These are the preparations of drugs in media
which may be aqueous, alcoholic, or glycerin.
They are applied to the mucous membrane
of throat or nose with an atomizer.
The throat sprays must be sprayed from a
special type of atomizer known as a
nebulizer, which removes the large droplets
by baffling system. Only precaution should be
taken that the fine droplet will used to easily
reach the lungs.
Nebulizer
45. InhalationsInhalations
These are liquid preparations containing volatile substance & are used to
relieve decongestion & inflammations of respiratory tract.
The volatile substance in inhalations would be volatile at room
temperature so that they should be placed on some adsorbent pad or
handkerchief.
In some cases inhalations will added to hot water (650
c) then vapors will
inhaled.
46. Nasal dropsNasal drops
Drugs in solution may be instilled into the nose from a dropper or
from a plastic squeeze bottle.
The drug may have a local effect, e.g. antihistamine, decongestant.
Alternatively the drug may be absorbed through the nasal mucosa
to exert a systemic effect.
The use of oily nasal drops should be avoided because of possible
damage to the cilia of the nasal mucosa & if it is used for long
period may reach the lungs & cause lipoid pneumonia.
To avoid that Nasal drops are prepared so that they are similar in
many respects to nasal secretions, so that normal ciliary action is
maintained thus aqueous nasal solutions usually are isotonic and
slightly buffered to maintain a pH of 5.5 to 6.5.
47. Eye dropsEye drops
Sterile, aqueous/oily solutions or suspensions intended for
instillation in eye sac.
Eye drops may contain buffers, stabilizing agents, dispersing agents,
solubilising agents, anti-oxidants & agents required for tonicity/
viscosity adjustment
Single dose container should not contain anti-microbial
preservative.
In case of multi dose container a dropper should be supplied with
it for administration. Maximum size of such containers is 10 ml.
48. Eye lotionsEye lotions
These are the aqueous solutions used for washing the eyes.
These are supplied in concentrated forms & are required to diluted with
warm water immediately before use.
They should be free from foreign particles to avoids irritation to the
eye.
They are required to prepared fresh & should not be stored for more
than two days to avoid microbial contaminations.
49. Ear dropsEar drops
These are the solutions of drugs that are instilled into ear cavity with the
help of dropper.
These are generally used for cleaning the ear, softening the wax & for
treating the mild infections.
The solutions is generally prepared in water, glycerin, propylene glycol &
dilute alcohol.
50.
51.
52. Biphasic liquid dosage formsBiphasic liquid dosage forms
The liquid which consist of two phases are known as a biphasic
liquid dosage forms.
They are sub categorized into two different forms namely as –
I) Emulsion
II) Suspension
In emulsion both phases are available in liquid where as in
suspension, finely divided solid particles are suspended in liquid
medium.
53. EmulsionEmulsion
Emulsion is a biphasic liquid preparations containing two immiscible
liquid (Continuous Phase & dispersed phase) made missicible.
The liquid which is converted into minute globules is called as dispersed
phase & the liquid in which the globules are dispersed is called the
continuous phase
dispersed phase
continuous phase
Two Immiscible Liquids
Dispersed Phase
(Internal phase)
Continuous Phase
(External phase)
An emulsion is a thermodynamically unstable system consisting of at least
two immiscible liquid phases one of which is dispersed as globules in the
other liquid phase stabilized by a third substance called emulsifying agent.
The globule size in emulsion varies from 0.25 to 25 µm.
54. Examples for emulsions:- milk, rubber latex, crude oil etc.
A.: Two immiscible liquids not emulsified
B. An emulsion of phase B dispersed in Phase A
C. Unstable emulsion slowly separates.
D. The emulsifying agent ( black film) places it self on the interface between
phase A and phase B and stabilizes the emulsion.
55. Types of emulsionsTypes of emulsions
Simple type
Water in oil (w/o)
Oil in water (o/w)
Depending on globule size
Micro emulsion
Fine emulsion
Special type
Multiple emulsion (w/o/w, o/w/o)
56. Water in oil (w/o)Water in oil (w/o)
In this types of emulsion water is dispersed phase & oil is continuous
phase
w/o types of emulsion generally meant for External use.
Examples are butter, lotions, creams etc.
In rare case they are used internally.
Water is dispersed
phase
Oil is continuous phase
57. Oil in water (o/w)Oil in water (o/w)
In this types of emulsion oil is dispersed phase & water is continuous
phase
o/w types of emulsion meant for both Internal use & External use.
Examples for internal use are Vitamin A in corn oil, liquid paraffin in
water etc.
Examples for External use are Benzyl benzonate emulsion.
Oil is dispersed phase
water is continuous phase
58. Micro EmulsionMicro Emulsion
These are clear dispersions of o/w or w/o in which the globules have small
size like as a 10nm or 0.01 µm..
Being cleared products micro emulsion are more popular now a days.
Micro emulsions are thermodynamically stable optically transparent ,
mixtures of a biphasic oil –water system stabilized with surfactants.
59. Fine emulsionFine emulsion
Normally these have a milky appearance.
The globule size ranges from 0.25 to 25 µm.
60. Multiple emulsionMultiple emulsion
These are emulsion with in emulsion & designated as w/o/w or
o/w/o.
The drugs that is incorporated in the innermost phase must cross
two phase boundaries before getting absorbed.
It is generally used in oral sustained release or intramuscular
therapy.
61.
62. The following methods are used for the preparation of emulsions on a
small scale.
1.Dry gum method
2. Wet gum method
3. Bottle method
4. Other methods
63. Dry gum method:
1.Measure the required quantity of oil in a dry measure and transfer in to
mortar.
2.Add calculated quantity of gum acacia in to mortar and triturate to form a
uniform mixture.
3.Add water and triturate vigorously till the clicking sound is produced in the
product becomes white.
4.The emulsion produced this stage is known as primary emulsion.
5.Ratio of oil water gum
Fixed oil-4:2:1(Caster oil, Arachis oil)
Volatile oil-2:2:1(Peppermint oil, Cinnamon oil)
Mineral oil-3:2:1(Liquid paraffin)
Ex: Arachis oil emulsion
64. Wet gum method:
1.Powder the gum acacia in in a mortar. Add water and triturate it with gum
so as to form a mucillage.
2.Add the required quantity of oil in small proportions with rapid trituration
until the clicking sound is produced and the water becomes white.To get a
primary emulsion
3.Add more water and triturate to produced required volume.Stirr thoroughly
so as to form a uniform emulsion.
Ex: Caster oil emulsion
Bottle Method:
It is used for the preparations of volatile and other non-viscous oils.
Measure the oil and transfer in to large bottle.
Add required quantity of gum acacia.
Shake the bottle vigorously until oil and gum mixed thoroughly.
Add water and shake the mixture vigorously to form a primary emulsion.
65. Other Methods:
Various blenders and homogeniser used for preparing emulsions.
Hand homogeniser,colloidal mill are some of the homogeniser used for the
preparations of emulsions.
The principle is large globules coarse emulsion are broken in to smaller
globules by passing them under pressure.
A coarse emulsion is prepared in a mortar which is transferred in to hand
homogeniser.
68. Dilution testDilution test
The emulsion is diluted with water, after dilution emulsion remain stable
then it is said to be o/w type of emulsion because water is in continuous
phase. If emulsion is break after dilution with water then it is said to be
w/o type of emulsion.
Add drops of water
Water distribute
Uniformly
Add drops of water
O/W Emulsion W/O Emulsion
69. Conductivity testConductivity test
Conductivity test can be performed by dipping a pair of electrode
connecting with low voltage bulb & pass the current.
If bulb glows then it is said to be o/w type of emulsion because water is
in continuous phase & it is good conductor of electricity.
If bulb doesn't glow then it is said to be w/o type of emulsion because oil
is bad conductor f electricity.
Bulb glows with O/W
Emulsion
Emulsion
Bulb doesn’t glow with W/O
70. Dye testDye test
Oil soluble Scarlet red dye is mixed with emulsion.
Place a drop of emulsion on microscopic slide cover it with cover
slip & examine under microscope.
If disperse globules appears red & ground is colourless then it said
to be o/w type of emulsion because water is present in continuous
phase.
If reserve condition occurs (If disperse globules appears colourless
& ground is red colour then it said to be w/o type of emulsion
because oil is present in continuous phase.)
Oil is dispersed phaseWater is
continuous phase
Water is disperse phase
Oil is continuous
phase
71. Fluorescence testFluorescence test
Certain fixed oil posses the physical properties of fluorescing in the
presence of ultraviolet radiations.
If examine under microscope ground is fluorescence then it said to be
w/o type of emulsion because oil is present in continuous phase.
If examine under microscope droplet is fluorescence then it said to be
o/w type of emulsion because oil is present in disperse phase.
72. Creaming testCreaming test
The direction of creaming identifies the emulsion type, if the densities
of aqueous and oil phases are known.
Water-in-oil emulsions normally cream downward as oil is usually less
dense than water.
Oil-in-water emulsions normally cream upwards.
73. Cobalt chloride testCobalt chloride test
Pour the emulsion on filter paper then it is soaked in cobalt chloride
solutions & allowed to dry turns from blue to pink.
Then this emulsion is said to be o/w type of emulsion.
This test may fail if emulsion unstable or breaks in presence of
electrolyte.
74. Filter paper testFilter paper test
This test is based on the fact that an o/w emulsion will spread out
rapidly when dropped onto filter paper.
In contrast, a w/o emulsion will migrate only slowly. This method
should not be used for highly viscous creams.
75.
76. SuspentionSuspention
Suspensions are the biphasic liquid dosage forms
of medicament in which finely divided solid
particles ranging from 0.5 to 5 micron are
dispersed in a liquid or semisolid vehicle, with
aid of single or combination of suspending
agent.
In which solid particles acts as disperse phase
where as liquid vehicle acts as continuous phase
The external phase (suspending medium) is
generally aqueous in some instance, may be an
organic or oily liquid for non oral use.
The particle size for non oral suspension is so
important to avoid grittiness to skin.
77. Advantage of suspensionAdvantage of suspension
Suspension can improve chemical stability of certain drug. E.g.
Procaine penicillin
Drug in suspension exhibits higher rate of bioavailability than other
dosage forms.
Solution > Suspension > Capsule > Compressed Tablet >
Coated tablet
Duration and onset of action can be controlled. E.g. Protamine
Zinc-Insulin suspension.
Suspension can mask the unpleasant/ bitter taste of drug. E.g.
Chloramphenicol
78. Disadvantage of suspensionDisadvantage of suspension
Physical stability , sedimentation and compaction can causes problems.
It is difficult to formulate.
Uniform and accurate dose can not be achieved unless suspension are
packed in unit dosage form.
All suspensions are required to be shaken before measuring of dose.
The storage of suspension may lead to changes in disperse system
especially, when there is fluctuations in temperatures.
79. Ideal qualities of good suspensionIdeal qualities of good suspension
It should settle slowly & easily re – dispersed on shaking
It should readily & evenly pour from container.
It should be chemically inert.
It should not forms hard cake.
It should prevent degradation of drug or to improve stability of drug.
It should mask the taste of bitter of unpleasant drug.
80. Ideal qualities of good suspensionIdeal qualities of good suspension
It should settle slowly & easily re – dispersed on shaking
It should readily & evenly pour from container.
It should be chemically inert.
It should not forms hard cake.
It should prevent degradation of drug or to improve stability of drug.
It should mask the taste of bitter of unpleasant drug.
81. 2.On the basis of proportion of solids:
i)Dilute suspension:
It comprise of 2-10%W/V of solid constituents.
e.g:. Prednisolone acetate
ii) Concentrated suspension:
It comprise of 50%W/V of solid constituents.
e.g:. External and Parenteral application.
3. On the basis of nature and behavior of solids:
i) Flocculated suspensions:
The system involves chemical bridging between the particles to form
aggregates.
Weak van der waal attraction forces are present in between these light and
fluffy aggregates.
Aggregation can be facilitated through adding flocculating agents.
Flocculation can be attained by adding extra anions.
82. Flocculated suspensionFlocculated suspension
In this type, solid particles are loosely aggregates themselves, means
individual particles are come in contact with each other to forms network
like structure called as a floccules.
These flocs are light, fluffy in nature, which are held together by weak van
der waals force of attraction.
Aggregation is achieved by adding flocculating agent.
This suspension will readily sediments.
This suspension posses better physical stability but less bioavailability as
compared to deflocculated suspension due to dissolution of floccules.
83. Deflocculated suspensionDeflocculated suspension
In this type of suspension, individual particle exits as a separate entity, means
particles carry a finite charges on their surface . Hence particles approaches
each other, they experience repulsive forces. This force create a high
potential barrier, which prevents a aggregation of particles.
During storage, these suspension shows a sedimentation at slow rate, due to
that particles forms a close packing arrangement.
So that it is difficult to re dispersed on agitation & forms a cake or claying
which is hard in nature.
This type of suspension have shorter shelf life but high bioavailability as
compared to flocculated suspension.
84. Difference between flocculated & deflocculated suspensionDifference between flocculated & deflocculated suspension
Flocculated Suspension Deflocculated suspension
Particles form loose aggregates & forms
network like structure.
Particle exist as separate entities.
Particles experience attractive forces. Particles experience repulsive forces.
Supernatant liquid is clear. Supernatant liquid is cloudy.
The rate of sediment is high. The rate of sediment is slow.
Sediment is rapidly formed. Sediment is slowly formed.
sediment are loosely packed, hence hard
cake is not formed.
Sediments are closely packed, hence
hard cake is formed.
The sediment is easy to redisperse on
shaking.
Sediment is difficult to redisperse on
shaking. (due to formation of hard cake)
Bioavailability is comparatively less. Bioavailability is relatively high.
The suspension is not pleasing in
appearance.
The suspension is pleasing in
appearance.
85. Formulation of suspensionsFormulation of suspensions
Formulation problemsFormulation problems
1. Sedimentation.
2.Thermodynamic instability.
3.Wetting.
03/09/19
86. SedimentationSedimentation
• The factors affecting the rate of sedimentation are in Stokes' equation:
• Where v= velocity of sedimentation of a spherical particle of radius r, and
density σ, in a liquid of density ρ, and viscosity , and where g is theŋ
acceleration due to gravity.
03/09/19 BA-FP-JU-C
88. WettingWetting
The insoluble medicament may be :
• Diffusible solids (dispersible solids): These are insoluble solids that
are light and easily wetted by water. They mix readily with water,
and stay dispersed long enough for an adequate dose to be
measured. After settling they redisperse easily. Examples include
magnesium trisilicate, light magnesium carbonate, bismuth
carbonate and light kaolin.
• Indiffusible solids: Most insoluble solids are not easily wetted, and
some particles may form large porous clumps in the liquid,
whereas others may remain on the surface. These solids will not
remain evenly distributed in the vehicle long enough for an
adequate dose to be measured. They may not redisperse easily.
Examples for internal use includes aspirin, phenobarbital,
sulfadirnidine and chalk, and for external use calamine,
hydrocortisone, su1phur and zinc oxide.
03/09/19 BA-FP-JU-C
89. WettingWetting
Because of the high interfacial tension between indiffusible
solids and water; air may be trapped in these poorly wetted
particles which causes them to float to the surface of the
preparation and prevents them from being readily dispersed
throughout the vehicle.
Wetting of the particles can be encouraged by reducing the
interfacial tension between the solid and the vehicle, so that
adsorbed air is displaced from solid surfaces by liquid.
Suitable wetting agents have this effect, but decrease inter-
particular forces thereby affecting flocculation.
03/09/19 BA-FP-JU-C
90. WettingWetting
Wetting agents:
Hydrophilic colloids such as acacia and tragacanth can act as
wetting agents. However, care should be taken when using
these agents as they can promote deflocculation.
Intermediate HLB (hydrophilic-lipophilic balance) surfactants
such as polysorbates (tweens) and sorbitan esters (spans) are
used for internal preparations. Sodium lauryl sulphate and
quillaia tincture are used in external preparations.
Solvents such as ethanol, glycerol and the glycols also facilitate
wetting.
03/09/19 BA-FP-JU-C
91. Suspending agentsSuspending agents
Suspending agents increase the viscosity of the vehicle, thereby
slowing down sedimentation.
Most agents can form thixotropic gels which are semisolid on
standing, but flow readily after shaking.
Care must be taken when selecting a suspending agent for oral
preparations.
Suspending agents can be divided into five broad categories:
natural polysaccharides, semi-synthetic polysaccharides, clays,
synthetic thickeners and miscellaneous compounds.
03/09/19 BA-FP-JU-C
92. Suspending agentsSuspending agents
Natural polysaccharidesNatural polysaccharides
The main problem with these agents is their natural variability
between batches and microbial contamination.
These materials should not be used externally as they leave a sticky
feel on the skin.
They include tragacanth, acacia gum, starch, agar, guar gum,
carrageenan and sodium alginate.
Tragacanth:
Is a widely used suspending agent and is less viscous at pH 4-7.5.
As a rule: 0.2g tragacanth powder is added per 100 mL suspension or
2g compound tragacanth powder per 100 mL suspension. Compound
Tragacanth Powder BP 1980 contains tragacanth, acacia, starch and
sucrose and so is easier to use.
Tragacanth powder requires to be dispersed with the insoluble
powders before water is added to prevent clumping .
03/09/19 BA-FP-JU-C
93. Suspending agentsSuspending agents
Semi-synthetic polysaccharidesSemi-synthetic polysaccharides
These are derived from the naturally occurring polysaccharide
cellulose.
Examples include
Methylcellulose (Cologel ®, Celacol®)
Hydroxyethylcellulose (Natrosol 250®)
Sodium carboxymethylcellulose (Carmellose sodium®)
Microcrystalline cellulose (Avicel®).
03/09/19 BA-FP-JU-C
94. Suspending agentsSuspending agents
ClaysClays
These are naturally occurring inorganic
materials which are mainly hydrated silicates.
Examples include bentonite and magnesium
aluminium silicate (Veegum®).
03/09/19 BA-FP-JU-C
95. Suspending agentsSuspending agents
Synthetic thickeners:
•These were introduced to overcome the variable quality of
natural products.
•Examples include:
Carbomer (Carboxyvinyl polymer, Carbopol®),
Colloidal silicon dioxide (Aerosil®, Cab-o-sil®)
Polyvinyl alcohol (PVA).
Miscellaneous thickeners:
Gelatin used as a suspending agent and a viscosity increasing
agent
03/09/19 BA-FP-JU-C
96. Containers for suspensionContainers for suspension
Suspensions should be packed in amber bottles,
plain for internal use and ribbed for external use.
There should be adequate air space above the
liquid to allow shaking and ease of pouring.
A 5 mL medicine spoon or oral syringe should be
given when the suspension is for oral use.
03/09/19 BA-FP-JU-C
97. Special label and advice for suspensionSpecial label and advice for suspension
The most important additional label for suspensions is
'Shake well before use',
Store in a cool place. Stability of suspensions may be
adversely affected by both extremes and variations of
temperature.
Some suspensions. such as those made from
reconstituting dry powders, may need to be stored in
a refrigerator.
Extemporaneously prepared and reconstituted are
required to be recently or freshly prepared, with a 1-
4-week expiry date.
03/09/19 BA-FP-JU-C
98. A simple example,A simple example,
Chalk Mixture, Paediatric BP. Mitte 100mlChalk Mixture, Paediatric BP. Mitte 100ml
Master formula 100ml
Chalk 100mg 2g
Tragacanth 10mg 200mg
Syrup 0.5ml 10ml
Concentrated cinnamon
water 0.02ml 0.4ml
Double strength chloroform
water 2.5ml 50ml
Water to 5ml to 100ml
03/09/19 BA-FP-JU-C
99. SummationSummation
Suspensions can be used to administer an
insoluble solid by the oral route.
Suspensions may be used to replace tablets, to
improve dissolution rate, to prolong action and
to mask a bad taste.
Solids may be diffusible or indiffusible and require
different dispensing techniques.
Stokes' equation can be applied when formulating
a suspension to help ensure accurate dosage of
the drug.
Flocculated particles settle quickly and redisperse
easily, whilst deflocculated particles settle slowly
but tend to cake.
03/09/19 BA-FP-JU-C
100. SummationSummation
Hydrophobic solids may require wetting agents.
Suspending agents are added to slow down the
rate of settling of the solid.
Suspending agents may be natural
polysaccharides, semi synthetic polysaccharides,
clays or synthetic polymers.
Some suspensions are made by adding water to
reconstitute manufactured powders when
stability is a problem.
Shake well before use' and 'Store in a cool place‘
should be part of the labels on a suspension.
Inhalations are suspensions of a volatile material
adsorbed onto a diffusible solid.
03/09/19 BA-FP-JU-C
101.
102. Semisolid dosage formsSemisolid dosage forms
Semisolid dosage forms meant for external application
Semisolid dosage forms subcategorized are as-
I) ointment
II) creams
III) paste
IV) Jellies
V) Suppositories
The suppositories are also included in this category but it is a unit
dosage forms.
103.
104. OintmentOintment
Ointment are semisolid preparation meant for application to skin or
mucous membrane.
The ointments are mainly used for their protective or emollient
properties
It may be defined as a medicament or medicaments dissolved,
suspended or emulsified in ointment base.
There is no single ointment base which possesses all the qualities of
ideal ointment base, so it become necessary to use more than one
ointment base in the preparation of ointment.
105. Qualities of ideal ointment baseQualities of ideal ointment base
It should be inert, odourless & colourless & smooth.
It should be physically & chemically stable.
It should be compatible with the skin & with incorporated medicaments.
It should be of such consistency that it spread & soften when applied to
skin with stress.
It should not retard healing of wound.
It should produce irritation or sensitization of the skin.
106. Classification of ointment baseClassification of ointment base
Oleaginous bases
Absorption bases
Emulsion bases
Water soluble bases
107. Oleaginous baseOleaginous base
These bases consist of water soluble hydrocarbons, vegetable oils,
animal fats & wax.
The constituents of hydrocarbon bases are soft paraffin, hard
paraffin & liquid paraffin.
The vegetable oils are mainly used in ointment to lower the
melting point or to soften the bases.
These bases serve to keep the medicaments in prolonged contact
with the skin & also act as occlusive dressings. They have a low
capacity to absorb water & are used chiefly for their emollient
effect.
These bases losing their importance now a days for the many
reason.
108. Disadvantages of oleaginous basesDisadvantages of oleaginous bases
They are greasy.
They are sticky & are difficult to remove both from skin & clothing.
They retain body heat which may produce an uncomfortable feeling of
warmth.
They do not help in the absorption of medicaments.
109. Absorption basesAbsorption bases
These bases are generally anhydrous substance which have the
property of absorbing considerable quantities of water but still
retaining their ointment like consistency.
The absorption bases are of two type namely as
I) Non emulsified bases
II) Water in oil emulsion
Non emulsified bases absorb water & aqueous solutions producing
w/o emulsion. E.g. Wool fat, wool alcohol, beeswax & cholesterol.
Water in oil emulsions are capable of absorbing more water &
have the properties of non- emulsified bases. E.g. hydrous wool fat
( lanoline)
110. Emulsion basesEmulsion bases
These bases are semisolid or have cream like consistency.
Both o/w or w/o emulsions are used as a ointment base.
The o/w emulsion base is more popular now days because ease of
application will easily achieved.
The w/o type of emulsion bases are greasy & sticky.
The emulsifying ointment is prepared from emulsifying wax, white soft
paraffin & liquid paraffin.
111. Water soluble basesWater soluble bases
These are commonly known as greaseless ointment bases.
The water soluble bases consist of water soluble ingredients such as
carbowaxes ( polyethylene glycol polymer)
The carbowaxes are water soluble, non – volatile & inert substance.
Selection of appropriate carbowaxes is depend on their molecular
weight.
112.
113. Types of methodTypes of method
Trituation method
Fusion method
Chemical reaction method
Emulsification method
114. TRITURATION METHODTRITURATION METHOD
It is the most commonly used method for the preparationn of
ointments.
The method is used when the base is soft and the medicament is
insoluble in base.
So for uniform mixing of medicament in the base ,it bacomes
necessary to reduce the medicament to fine powder.
115. Fusion methodFusion method
When an ointment base contains a number of solid ingredients of
different melting points, such as white beeswax,stearic acid,hard
paraffin and cetyl alcohol,it is necessary to melt them in decreasing
order to their melting point.
This will avoid the over heating of the substances having low
melting points.
116. Chemical reaction methodChemical reaction method
Certain chemical reactions are involved in the preparation of
several ointments.
For example, iodine ointment.
Iodine may be present in free form or in combined formwith the
ointment base.
117. Emulsification methodEmulsification method
In this method the fats,oils,and waxes are melted together on a
water bath at a temperature of 70 degree Celsius.
The aqueous solution of all the heat stable water soluble
component is also heated almost at the same temperature as that
of the melted base.
118. CreamsCreams
These are viscous semisolid emulsions which are meant for external
use.
Cream is divided in to two types namely as
I) Aqueous creams
II) Oily creams
In case of aqueous creams the emulsions are o/w type & it is relatively
non greasy. The emulsifying waxes are anionic, cationic & non –ionic
used. Generally polysorbate, triethanolamine soap are used as
emulsifying agent.
In case of oily creams w/o type & it is relatively greasy. The
emulsifying agent such as wool fat, wool alcohols, beeswax & calcium
soap is used.
The cream should be store in collapsible tube & supplied in well
closed container to prevent evaporation & contamination.
119.
120. PastesPastes
Pastes are semisolid preparations intended for
external application to skin.
The pastes are generally very thick & stiff.
They do not melt at ordinary temperature & thus
forms a protective coating over the area where
they are applied.
Pastes are differ from ointment as they contain a
high proportion of finely powdered medicaments.
They are mainly used as a antiseptic, protective,
soothing dressings.
Pastes should be stored & supplied in containers
made of materials which do not allow absorption
or diffusion of content.
121. Paste basePaste base
Hydro carbon:
Soft paraffin and liquid paraffin are commonly used
bases for the preparation of paste.
Water miscible bases:
Emulsifying ointment is used as water miscible base
for the preparation of pastes
Water soluble bases:
Suitable combined of high and low molecular weight
polyethylene glycols are mixed together to get product of desired
consistancy.
122.
123. SuppositoriesSuppositories
Suppositories are solid dosage form of medicament for insertion
into body cavities other than mouth.
They may be inserted into rectum,vagina or nasal cavity
suppositories are available in different shapes, sizes and weights.
Suppositories are used to produce local, systemic and mechanical
action.
124. ADVANTAGES:
1) THESE ARE INSERTED INTO THE RECTUM TO
EXERT A DIRECT AND RAPID ACTION ON THE RECTUM .
2 )THESE ARE INSERTED INTO THE RECTUM TO
PROMOTE EVACUATION OF THE BOWL .
DISADVANTAGES:
1) THE IRRITANT DRUGS CAN’T BE ADMINISTERED BY
THIS ROUTE.
2) SUPPOSITORIES CAUSE EMBARRASSMENT TO THE
PATIENT, WHEN A DRUG IS ADMINISTERED BY INSERTING A
SUPPOSITORY INTO A BODY CAVITY .
125. TYPES OF SUPPOSITORIESTYPES OF SUPPOSITORIES
RECTAL SUPPOSITORIES : These are meant for
introduction into the rectum for their systemic action.
VAGINAL SUPPOSITORIES:These are meant for
introduction into the vagina.These suppositories are also know as
pessaries and are larger than rectal suppositories.
NASAL SUPPOSITORIES:These are meant for introduced
into the nasal cavity and are also know as nasal bougies.
URETHRAL SUPPOSITORIES:These are meant for
introduced the urethra and also known as urethral bougies.
EAR CONES:These are meant for introduction into the ear and
and also known as aaurinaria.
126.
127. Types of basesTypes of bases
Fatty bases
Water soluble and water miscible bases
Emulsifying bases
128. Fatty basesFatty bases
Theobroma oil: It is a yellowish white solid obtained from crushed
and roasted seeds of theobroma cocoa.
It also called as cocoa buttter.
It has butter like consistency having melting point of 30 to 35
degree celsius.
It is a mixture of glycerol ester of of stearic ,oleic,palmitric and
other fatty acids.
Theobromal oil melts at body temperature and release the
medicament for rapid absorption.
It is readily liquefy on warming and quickly settle on cooling.
129. DisadvantagesDisadvantages
It melts in warm weather.
It has the tendency to stick to the sides of the mould when
solidified.
The leakage from the body cavities on melting can take place.
It is relatively costly.
It is immiscible with body fluids.
It shows the phenomena of polymorphism i.e., when theobroma
oil is melted and cooled, it gets solidified into different crystalline
forms depending upon melting temperature ,rate of cooling and
size of the mass.
130. Emusified theobroma oilEmusified theobroma oil
This may be used as abase when large quantity of aqueous
solutions are to be incorporated.
The use of 5% glyceryl monostearate,10% lenette wax ,2-3% cetyl
alcohol,4% beeswax and 12% spermaceti is recommended to
prepare emulsified theobroma oil suppositories.
131. Hydrogenated oilsHydrogenated oils
These are obtained by dehygenation of various vegetables,such as
arachi’s oils,cotton seed oils,coconut oils,palm oils,etc.,
Advantages:
They are resistant to oxidation.
Lubrication of the moulds is not required.
Over heating does not affect the solifying point.
Disadvantages:
The suppositories become brittle on rapid cooling in a
refrigerator.
132. Water soluble and water miscibleWater soluble and water miscible
basesbases
Glycero-gelatin bases:
It is a mixture of glycerine and water which is made stiff by the
addition of gelatin.
The bases may be for preparing all types of supositories but it is
particularly used for making pessaries.
Soap-glycerin bases:
In glycero-gelatin bases,the gelatin is replaced with either curd
soap or sodium stearate which makes the base sufficiently hard to
prepare good quality of suppositories.
Soap also helps in the evacuation action of glycerin.
133. Polyethylene glycol:
Polyethylene glycol polymers are commonly known as carbowaxes
or polyglycol or macrogols.
The physical character of these carbowaxes varies according to the
molecular weight.
The macrogals having molecular weight less than 1000 are liquids
and those with molecular weight higher than 1000 wax like solids.
Advantages:
They are chemically stable.
They are non irritant.
They do not allow to bacteria or mould growth to take place.
They are physically inert substances.
134. Emusifying basesEmusifying bases
Witepsol: They consist of triglycerides of saturated vegetable
acid with varying percentage of partial ester.
A small amount of beeswax is used for in hot climates.
Massa estarinum: It is a mixture of mono ,di and triglycerides of
saturated fatty acids. This also known as adeps solidus.
Massuppol: It consist of glyceryl esters mainly of lauric acid to
which small amount of glyceryl monostearate has been added to
improve its water absorbing capacity.
Disadvantages:
They should be cooled rapidly in a refrigerator because they
become brittle.
They are not very viscous on melting , so the medication
incorporated with the base settle down rapidly.
135. PESSARIESPESSARIES
These are solid preparations containing one or more active
incredients and are suitable for vaginal insertion.They are intented
for as use as a single dose.
Types of pessaries:
Compressed pessaries
Moulded pessaries
136. Compressed pessaries:
These are also known as vaginal tablets,have the general
charecteristics of uncoated tablets but usually large and of great
weight . It should be stored in a well cclosed containers ,protected
from moisture and being crushed.
Moulded pessaries:
These are manufactured by pouring the liquified mass containing
the medicaments and auxillary substances into moulds of suitable
volume and cooling inorder to solidify the mass.
Auxillary substances used are macrogols ,theobroma oil and
glycerogelatin bases.
137. JelliesJellies
Jellies are transparent or translucent, non greasy, semi solid preparations
mainly used for external application to skin.
These are also used for lubricating catheters, surgical gloves & rectal
thermometer.
The substance like gelatin, starch, tragacanth, sodium alginate & cellulose
derivatives are used for the formulation of jellies.
Jellies are of three types namely as
Medicated jellies
Lubricating jellies
Miscellaneous jellies
Gels: gels may be defined as semisolid
preparations which may contain small and
large of organic molecules dispersed in a
suitable liquid.
138.
139. Introduction
With the advancement of pharmaceutical sciences, a new concept have
evolved various modern dosage forms & methods of their
administration. Some of the modern dosage forms are
Implants
Films & strips
Liposome drug carriers
Controlled drug delivery modules
Erythrocytes
Nanoparticles
prodrugs
140. Implants These are hypodermic tablets are placed under the skin by a minor
surgery in order to release drugs over prolonged periods of time.
Now the magnetically controlled implants have been developed which
can be opened or closed at will in order to release or stop the drug.
These implants are placed at upper thigh at a depth of 5mm.
These implants are useful in hormone therapy.
141. Films & stripsThese are meant for topical application for slow release of drug over
predetermined period of time. Films & strips are more popular these
days. They are sub categorized in to following types namely as
Zero order release films
Buccal strips
Spray bandages
142. Zero order release films These are called as laminates & meant for topical application. E.g.
Nitroglycerine laminates are prepared by mixing propylene glycol
with about 1% carbopol resin. The mixture is neutralized with NaoH
solution & then 0.1% of nitroglycerin is added. It is then placed in
polythene sheet 5*5 cm & its edges are sealed by heat. It is then
placed on pressure sensitive adhesive sheet of 5.5 * 5.5 cm so that it
can be properly adhesive to skin. Such laminates release the drug
slowly into circulation for about 12 hours.
143. Buccal strips
The buccal & sublingual tablets are now replaced with buccal strips.
These strips consist of a thin absorbent base of fabrics, filter paper &
cotton etc.
The buccal strips are prepared by immersing a long piece of fabric
made from polyamide fibers into a molten mixture of carbowaxes &
dissolved or dispersed the drug.
The fabric is then cooled & cut into small pieces.
It should be contact with buccal mucosa for about 15 min. & then
removed & discarded.
144. Spray bandage
These bandage are prepared by spraying the solution of drug in
polylactide (polymer of lactic acid anhydride)
A solution of purified lactide polymer is made in chloroform.
It is then packed in aerosol container having suitable propellant.
When these solution sprayed then it will be a comfortable bandage
which can simply washed of with warm water.
145. Liposome drug carriers These are several carriers in our body which transport both to an
other like as enzymes, proteins etc.
These are phospholipids which can transport both hydrophilic &
hydrophobic drugs.
The large multilamellar vesicles (LMV), small unilamellar vesicles
(SUV), large unilamellar vesicles (LUV) are some of the liposome's
known today.
146. Applications
Used in diseases caused by intracellular parasites. E.g. malaria,
tuberculosis & amoebiasis.
It entrapped insulin is active orally & can be replaced by IM
administration of insulin.
It can be used to transport functional DNA/RNA molecules into cell.
It can be used to transport radio pharmaceuticals & immunological
products.
Liposomal daunomycin has longer duration of action than free
daunomycin which is used in the treatment of neoplasia.
147. Controlled drug delivery modules
These are the device which are formed by embedding the drug within
a polymeric matrix so that it gets released slowly to the body over a
long period of time.
It will formed drug – polymer complex & may be formulated in to
tablet, capsule or any other suitable formulation.
These modules are punctured before administration with leaser beam
to make a small orifice for release of the drugs.
The drugs is released from these modules by diffusion, osmosis or
chemical reactions.
These are applied to skin, implanted subcutaneously or inserted into
various body cavities.
148. Erythrocytes
Erythrocytes are tried in order to achieve controlled release of drugs.
The life span of erythrocytes are 120 days.
It can allow a drug to circulate in the body for long period of time
which help slow release of the drugs in to serum.
Released erythrocytes are prepared by putting them in to a hypotonic
medium. So that they can easily swollen.
The aqueous solutions of the drug is added to the medium so that
drugs gets in to erythrocytes through open pores.
When isotonicity is adjusted the erythrocytes shrink, thus
encapsulating the drug with in them. These erythrocytes may be
suspended in normal saline solutions for preparing injections.
149. Applications Released erythrocytes of urease have been used in kidney failure to
degrade serum urea.
Released erythrocytes of asparaginase have shown good result in
asparaginase dependent leukemia.
Released erythrocytes of methotrexate & adrianycin have been tried
in cancer therapy.
Released erythrocytes of prednisolone have shown good result to
prolong the anti-inflammatory action.
150. Nanoparticles
It is based on colloidal drug delivery system.
The particles size of this system is in nanometer range (200 – 500
mm)
The system consist of a drug & carriers to deposit the drug at target
site.
The carriers used are naturally occurring macromolecules like human
serum albumin, bovine serum albumin, & other substances like
gelatin, casein & ethylcellulose.
151. Applications
Flourescein isothinocyanate (FITC) nanoparticles have been used to
incorporate cytotoxic agent into tumor cell in cancer chemotherapy.
Nanoparticles along with biological maker like immunoglobulin can
be used to target the drugs to very specific site.
152. Prodrugs
The compound which undergo biotransformation before showing
desired pharmacological activity are called prodrugs or proagents.
Prodrugs are generally the ester or amides of parent drugs.
These are useful to improving the stability, solubility, bioavailability
of drugs, masking the unpleasant taste & odour of the parent drug &
reducing the toxicity
153. Applications
Choramphenicol palmitate, the prodrug of chloramphenicol is used
in the preparation of pediatrics suspension because it has no bitter
taste.
Procaine penicillin G & benzathine penicillin G are prodrugs of
penicillin G which shows resistance to hydrolysis as compared to the
parent drug.
Cindamycin 2- phosphate the prodrug of cindamycin has no bitter
taste of parent drug.
The factors are: Particle size, greater the difference in density between the particles and vehic1e, the greater wi11 be the rate of descent. Increasing the viscosity of the dispersion medium, within limits so that the suspension is still pourable, will reduce the rate of sedimentation of a solid drug. Thus a decrease in settling rate in a suspension may be achieved by reducing the size of the partic1es and by increasing the density and the viscosity of the continuous phase.
The factors are: Particle size, greater the difference in density between the particles and vehic1e, the greater wi11 be the rate of descent. Increasing the viscosity of the dispersion medium, within limits so that the suspension is still pourable, will reduce the rate of sedimentation of a solid drug. Thus a decrease in settling rate in a suspension may be achieved by reducing the size of the partic1es and by increasing the density and the viscosity of the continuous phase.