Suspension pharmaceuticals.ppsx

Disperse pharmaceutical dosage forms
3/29/2022 1
By Abreham D

Disperse
system
29/2022 2
By Abreham D

1.2.2 Disperse systems
• Are liquid preparations containing undissolved or
immiscible drug through the vehicle.
• It has two components:
1. Dispersed phase/internal phase –the substance
distribute through the vehicle.
2. Dispersing phase /dispersion medium /continuous
phase/external phase or the vehicle.
3
3/29/2022 By Abreham D

Classification
• Based on the size of the dispersed phase:
• Coarse dispersion (10 – 50 µm)
• Fine dispersion (0.5 – 10 µm)
• Collodions dispersion (1nm - 1µm)
4

Note:
• For all dispersion systems complete & uniform
redistribution of the dispersed phase is essential to get
accurate dose.
• Therefore shaking or agitation is necessary.
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By Abreham D

• Solid particle that is insoluble in the external phase.
• Liquid dispersed phase i.e. insoluble &immiscible with
the medium.
• Small air bubble dispersed through the medium.
• Droplets of liquid dispersed in air
The system may contain;
6

1.2.2.1 Suspensions
• Pharmaceutical preparations where at least one of the
active ingredients is suspended throughout the vehicle.
• Mostly contains aqueous medium.
• Stabilizers may be available or not.
• Some are available as dry form.
• For good pharmaceutical suspension the particle size
should be b/n 1micrometer and 50 micrometers.
7

Classification
1. Based on application site
• Oral suspension
E.g. Paracetamol suspension, antacids
• Externally applied suspension
E.g. Calamine lotion.
• Parenteral suspension
E.g. Procaine penicillin G, Insulin Zinc Suspension
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By Abreham D

Classification con…
2. Based on Proportion of Solid Particles
• Dilute suspension (2 to10%w/v solid)
• Concentrated suspension (50%w/v solid)
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By Abreham D

Based on electro kinetic nature of Solid Particles
1. Deflocculated:
• The solid particles of the dispersed phase aggregate leading to
network like structure of the particles in the external phase;
• The solid drug particles settle slowly and cake formation will
happen.
2. Flocculated:
• The solid particles exist as separate entities in the dispersion
medium
• The solid drug particles settle rapidly. 10

Deflocculated
• Particles remain as discreet unit
• Slow rate of sedimentation
• Allow uniform dose to be taken
• Exist as separate entities
• Form closely packed sediment
• Compact and difficult to re-disperse
• Supernatant liquid is not clear
• Elegant appearance
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By Abreham D

Flocculated
• Particles form loose aggregates
• Rapid rate of sedimentation
• Danger of inaccurate dose
• Loosely packed sediment(easy to re-desperse)
• Supernatant liquid is clear and not elegant
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By Abreham D

Note:
•Suspensions are prepared by partially
flocculating and deflocculated to enable
adequate re-dispersion.
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By Abreham D

Basedon electro kinetic nature of Solid Particles….
Suspensions may bay be
• Indiffusible or
• Diffusible
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By Abreham D

1. Diffusible suspensions
Suspensions containing:
• Easily suspend particles
• Light and easily wettable with litle/without adding any
wetting agent and any suspending agent
• Easily diffuse evenly through the vehicle upon shaking.
E.g. calcium carbonate, light kaolin, light magnesium
carbonate & magnesium trisilicate.
15

2. Indiffusible suspensions:
Suspensions having particles:
• Not remain evenly distributed in the vehicle long enough to ensure
uniformity of dose
• The simplest way of correcting this problem is by:
increasing the viscosity of the vehicle by adding thickening
agents/ suspending agents.
E.g. Aspirin, chalk, phenobarbitone, calamine, hydrocortisone, zinc
oxide, sulphur precipitate…
16

Additives used in suspensions
A. Wetting agent:
• Insoluble solids exhibit varying degree of hydrophobicity, so
 Are not easily wetted
 Form a clump in the liquid
 Remain on the surface
 Attach to the container
• Therefore wetting agents importantly tackles these problems which
are adsorbed at the interface of solid –liquid.
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By Abreham D

B.Surfactants:
• It decreases the interfacial tension b/n the particles of the
dispersed and the dispersion phase.
• These are a useful wetting agent with HLB values b/n 7
and 9.
18

Example of surfactants,
• For oral use -polysorbates , Sorbitan esters
• For external -sodium lauryl sulphate
-sodium dioctylsulphsuccinate
• For parenteral - polysorbates
- Lecithin
- Hydrophilic colloids
- Propylene copolymers
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By Abreham D

C. Thickening/viscosity enhancing or suspending agents:
• These are added to enhance the thickness/viscosity of
the external phase.
• Added to
 Reduce the rate of sedimentation
 Prolong contact time for ophthalmic preparations
 Thicken externally applied preparations
20

Classification of suspending agents
I. Natural polysaccharides
Acacia
• Dry exudates from stem & branch of various species of
acacia
• Low thickening property
• Sticky & rarely used in externally
21

Tragacanth
• Forms viscous aqueous solutions
• Better than acacia due to thixotopic & pseudo plastic
nature
• Used for internal & external preparation
• Compound of tragacanth powder consists of acacia,
tragacanth,starch, & sucrose
22

Alginates
• Similar to tragacanth
• Sodium alginate is mostly used
Starch
• Can also used with carmellose sodium
• Rarely used alone
• Mostly combined with tragacanth and sodium
carboxycellulose
23

II. Semi synthetic polysaccharides
• xanthan gum and
• Water soluble cellulose
• Hydrated silicates/clays
24

1. Xanthan gum
• Sodium salt of partially acetylated polysaccharide of
high molecular weight
• soluble in cold and hot water
• Can form suspensions of better quality
• Alternative to tragacanth
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By Abreham D

2. Water soluble celluloses
A. Methyl cellulose
• Semi synthetic polysaccharide
• Prepared by methylation of cellulose
• More soluble in cold water than hot
• Stable in a wide range of ph (3-11)
• Compatible with many ionic excepients
• Gels on heating
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By Abreham D

B. Hydroxyethyle cellulose
• Hydroxyethyle group attached to cellulose
• soluble both in hot & cold water
• Not gel on heating
27

C. Carmellose sodium (sodium carboxy methyl
cellulose)
• Produces clear solution in cold & hot water(stable
PH 5-10)
• Anionic and incompatible with polyvalent cations
• Used for oral ,parenteral & external
28

D. Microchrystalline cellulose
• Consists of easily dispersing colloids in water
• Widely used agent
29

3. Hydrated silicates/clays
• Hydrates easily absorb water 12 times its weight
• Anionic so incompatible with cationic substances
• A good suspending agent
Example
Bentonite, & hectorite  for external use
Aluminum magnesium silicate carbomers (carboxyl
propylene)  for both internal and external
30

III. Synthetic
1. Colodion silicone dioxide
• Finely divided solids
• Forms three dimensional aggregate
• Used for non aqueous suspensions as thickening agent
31

Reasons for Suspensions
• why suspensions are important?
• Some drug are unstable in solution but stable in
suspension
• Easy of swallowing liquids & flexibility in
administration for infants & extreme age groups
• In case of disagreeable tastes of drugs in solution
32

Features of desired in a pharmaceutical suspension
During a good pharmaceutical suspension preparation, the
following points should be considered (desirable properties):
• Should slowly settled
• The sediment formed on storage should be easily re-disperse
after gentile shaking
• The medicament should suspend for a long enough to measure
accurate dose
• Have small & uniform particle size
33

Con …
• It should be easy to pour yet not watery and no grittiness.
• It should have pleasing odour , colour and palatability.
• Good syringeability.
• Parenteral /Ophthalmic suspension should be sterilizable.
• Should easily & readily poured from the container
• Should have optimum physical, chemical & pharmacological
property
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By Abreham D

Suspensions with
optimum rate of
sedimentation
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By Abreham D

3/29/2022 36
Suspensions with
high rate of
sedimentation
By Abreham D

The major role of optimizing the particle size
• Decreasing particle size decrease rate of sedimentation
• Large particle sized drugs are easily settled;
• difficulty to provide accurate dose &
• imparts gritty texture to the product.
37

Preparations of suspensions
• Before the preparation of suspensions, ensure that the powder to
be suspended is:
• A suitably fine degree of division for adequate
bioavailability,
• Minimum sedimentation rate &
• palatability
• In extemporaneous preparations, the powdered drug should be
mixed with suspending agent & some of the vehicles using mortar
& pestle.
38

Con….
• At this stage it may also be necessary to add a wetting
agent to aid dispersion.
• Other soluble ingredients should then be dissolved in
another portion of the vehicle, mixed with
concentrated suspension
39

Method of suspension preparation
1. Direct incorporation
• Soluble components are normally dissolved in the
appropriate solvent.
• The solid therapeutic agent is then add with the aid of
mixing before adjusting the volume.
40

1. Direct incorporation Con….
• The mixing rate employed is a determinant factor:
 If the suspension is flocculated, high speed mixing may be
employed as the properties of the system are pseudo plastic.
 However, if the formulation has been poorly designed and has
poor flocculation properties, high speed of mixing will result
in an increase in the viscosity of the product
• The size of the suspended particle within the formulation may be
reduced using a ball mill.
41

2. Precipitation method
• In this method the drug is dissolved in the vehicle (a portion of it)
prior to precipitation following the addition of a counter ion
• The salt formed is insoluble such systems are frequently
deflocculated and are therefore mixed at slow shear rate.
• Th excepients are then dissolved in the vehicle which is then
added to the suspension of drug.
• To ensure homogeneity the formulation may be exposed to high
shearing rate.
42

Con….
• Finally the volume is adjusted by adding the required
mass of diluents.
• One problem with this technique is the production of
ionic by products from the precipitation interaction.
• If the concentration is too high, then the precipitated
therapeutic agent requires to be washed with an
aqueous solvent.
43

Extemporaneous compounding of suspensions
44

Packaging and storage condition of suspensions
• Packaging: all suspensions should be packed in a
wide mouth container having adequate air space above
the liquid to permit adequate shaking and easy of
pouring.
• Labeling: the most important additional label for
suspensions is “shake before use “
45

Con…
Storage:
• Most suspensions should be stored in tight containers
protected from freezing & excessive heat and light.
• Some suspensions such as those made for
reconstituting powder may need to be stored in
refrigerator
46

Examples of oral suspensions;
• Antacid susp, cotrimoxazole, metrynidazole ,
mebendazole , albendazole,…etc
• Are examples of suspension preparations to be taken
orally/ administered orally or
• Ready for direct use after adequate shaking without
adding any other diluents/vehicle .
47

Dry powder suspensions:
• Certain pharmaceutical suspensions are in stable when
prepared as liquid form
• So, should be prepared as dry powder.
• These are solid dosage forms but used as liquid dosage
form.
• But after diluted/reconstituted it forms suspension.
48

Dry powders may be
• For oral use with reconstitution with adequate shaking:
• Dry powders of amoxicillin, cloxacillin & erythromycin…..
• For parenteral use after reconstitution:
• Crystalline Pen. PPF , Ampecillin, Benzantine Pen G….
49

Calculation
Example
• Suppose you are requested to reconstitute procaine penicillin
fortified (ppf powder) in a vial; One vial of ppf (4mIU) is
reconstituted to become 10 ml suspension. There for during
admixture, this powder needs sterile water for injection. So
this medication to be reconstituted, we should add sufficient
quantity of water up to 10 ml. But if you have a prescription
600,000 IU PPF for IM administration, so how much ml of PPF
you will inject after it is reconstituted?
3/29/2022 50
By Abreham D

Given
Amount of 1 vial in ml= 10 ml
Amount of 1 vial in IU= 4,000,000 IU
Amount of PPF prescribed= 600,000 IU
Required
Amount of PPF in ml =?
Solution
1 vial =10 ml =4,000,000 IU
But how much is 600,000 IU in ml ?
10 ml = 4,000,000 IU
X = 600,000 IU
600,000 IU * 10 ml =4000,000 IU * X
600,000 IU * 10 ml = 4000,000 IU * X
4 000,000 IU 4000,000 IU
X = 6/4 ml
X= 1.5 ml
So the physician administers 1.5 cc of PPF for the patient after reconstituting the total powder within 10
ml.
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By Abreham D

Quality test of suspensions
• Rate of sedimentation
• Appearance
• Packaging and
• Other tests as in solutions
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By Abreham D

10Q for your
attention !
3/29/2022 53
By Abreham D

Suspension pharmaceuticals.ppsx

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