COARSE DISPERSION Flashcards
(82 cards)
1
Q
- Particle size between greater than 500 nm
- Visible under ordinary microscope
- Do not pass through filter paper
- Do not pass through semipermeable membrane
- Do not diffuse
A
COARSE DISPERSION
2
Q
Most pharmaceutical suspensions and emulsions are
A
coarse dispersions
3
Q
SUSPENSION
Insoluble Solid, internal
A
dispersed phase
4
Q
SUSPENSION
liquid, external
A
dispersion medium
5
Q
SUSPENSION
concentration of externally applied suspensions
A
.>20%
6
Q
SUSPENSION
concentration of Parenteral suspensions
A
0.5 - 30%
7
Q
Advantages of Pharmaceutical Suspension
Make insoluble drugs more ____
A
palatable
8
Q
Advantages of Pharmaceutical Suspension
Provide suitable dosage form for ____ to skin and mucous membrane while retaining the grittiness of the solid particle
A
dermatologic materials
9
Q
Advantages of Pharmaceutical Suspension
Parenteral administration of ____ drugs
A
water-insoluble
10
Q
Characteristics of an Acceptable Suspension
Suspended material should NOT ____
A
settle rapidly
11
Q
Characteristics of an Acceptable Suspension
Sediments do NOT for a ____
A
hard cake
12
Q
Characteristics of an Acceptable Suspension
____ when shaken
A
readily dispersed
13
Q
Characteristics of an Acceptable Suspension
Not too ____
A
viscous
14
Q
Characteristics of an Acceptable Suspension
for lotions:
Easily ____
A
spread
15
Q
Characteristics of an Acceptable Suspension
for lotions:
____ quickly
A
dry
16
Q
Characteristics of an Acceptable Suspension
for lotions:
have acceptable ____ and ____
A
color & odor
17
Q
Physical Stability of Suspensions
Particles do not ____
A
aggregate
18
Q
Physical Stability of Suspensions
They remain ____ throughout.
A
uniformly distributed
19
Q
Physical Stability of Suspensions
Easily resuspended by ____
A
moderate agitation
20
Q
light fluffy conglomerates held by weak van der Waals forces
A
flocs / floccules
21
Q
Properties of Suspended Particles
Tend to ____
A
flocculate
22
Q
flocs or floccules are held by
A
weak van der waals forces
23
Q
- particles adhere by stronger forces
- leads to CAKING
A
aggregates
24
Q
growth and fusing of aggregates
A
caking
25
# FLOCCU OR DEFLOCCU
Sediments are **loosely** packed
(FLOCS)
FLOCCULATED
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# FLOCCU OR DEFLOCCU
Sediment is **closely** packed (AGGREGATES) and forms a **hard cake**
DEFLOCCU
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# FLOCCU OR DEFLOCCU
Sediment **rapidly** forms
FLOCCU
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# FLOCCU or DEFLOCCU
Sediments **slowly** forms
DEFLOCCU
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# FLOCCU or DEFLOCCU
**High** sedimentation rate
(settles rapidly)
FLOCCU
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# FLOCCU or DEFLOCCU
**Low** sedimentation rate
(settles slowly)
DEFLOCCU
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# FLOCCU or DEFLOCCU
**Easily redispersed** when shaken
FLOCCU
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# FLOCCU or DEFLOCCU
**Difficult** to redisperse
DEFLOCCU
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# FLOCCU or DEFLOCCU
Pharmaceutically Elegant
FLOCCU
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**Velocity of sedimentation** is expressed by
STOKE'S LAW
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**Dilute** Suspension
FREE SETTLING
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.>5% Suspension
HINDERED SETTLING
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settle **more** rapidly
LARGER PARTICLES
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**Settling** in **flocculated** systems
SUBSIDENCE
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# **FORMULA**
sedimentation volume of **flocculated**
F = Vu / Vo
| Vu - final volume
Vo - original volume
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# **FORMULA**
sedimentation volume of **deflocculated**
F∞ = Vu / Vo
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* determines the **acceptability** of a solution
* more **fundamental** parameter
degree of flocculation
42
# **FORMULA**
degree of flocculation
*β* = F / F∞
| F - sedimentation volume flocculated
F∞ - sedimentation volume defloccul
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pharmaceutically acceptable
F ≥ 1
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# Components of Suspension
**surfactants** that **decrease** the **solid–liquid interfacial tension** and **contact angle** between the solid particles and the liquid vehicle.
wetting agents
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# Components of Suspension
* **Neutral electrolytes** that are capable of **reducing the zeta potential** of suspended charged particles to zero
* **increase** sedimentation volume
* to **electrify**
flocculating agents
46
# Components of Suspension
do **not** appreciably **lower** the **surface** and **interfacial tension** but are **used to produce deflocculated suspensions**
dispersing agents (deflocculants)
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# Components of Suspension
**retard settling** and **agglomeration** of the particles by functioning as an **energy barrier**, which **minimizes interparticle attraction**
suspending agents
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# SUSPENDING AGENTS
* Do **not** **reduce** interfacial tension
* Used in **low concentration** (0.1%)
* Forms **mechanical barrier** around particles
protective colloids
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# Preparation of Suspensions
applicable to only those drugs where **solubility depends on the pH value**.
pH precipitation
50
# Preparation of Suspensions
the **vehicle must be formulated** so that the **solid phase** is **easily wetted** and **dispersed**
dispersion method
51
# Preparation of Suspensions
Wetting agent + Vehicle → + Drug → Slurry → Sieved → Agitated → + Flocculating agent → Agitated → Allowed to settle → + Adjuvants → Dilute to final volume
CONTROLLED FLOCCULATION
52
A thermodynamically **unstable** system consisting of **at least two immiscible** liquids
emulsions
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# Pharmaceutical Emulsions
**Dispersed phase** (liquid) as
globules
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# Pharmaceutical Emulsions
**Dispersion medium** as
other liquid
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pharmaceutical **emulsions** are **stabilized** by
emulsifying agent
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# THEORIES OF EMULSIFICATION
the **interfacial tension** between two immiscible liquids is **reduced** by **surfactants**
surface tension theory
57
# THEORIES OF EMULSIFICATION
if **nonpolar** end of the emulsifying agent is **smaller**, the emulsion is **O/W**
oriented wedge theory
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# THEORIES OF EMULSIFICATION
emulsifying agent forms a **film** over one phase resulting to **globules**
interfacial film theory
59
* **surfactants reduce interfacial tension by adsorption** at the O/W interface to **form monomolecular film** (reduces coalescence)
* **reduction of the surface free energy** and the **tendency to coalescence**
* **combination** of **emulsifiers** rather than single agents are frequently used
MONOMOLECULAR ADSORPTION
60
**emulsion** is a **function** of the **relative solubility** of the **surfactant**
BANCROFT'S RULE
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* **finely divided wetted solids** by oil & water can **act as emulsifying agents**
* they form a film a **particulate film** around the **droplet** to **prevent coalescence**
Solid-particle adsorption
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**Dispersed Phase → Oil**
**Continuous Phase → Water**
* usually for **oral administration**
* emulsifiers: SLS, triethanolamine
oil in water O/W emulsion
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**Dispersed Phase → Water**
**Continuous Phase → Oil**
* usually for **external application**
* emulsifiers: sodium palmitate, sorbitan esters (Spans)
water in oil W/O emulsion
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* **complex polydisperse** systems
* **both** W/O & O/W **exist simultaneously** and are stabilized by lipophilic and hydrophilic surfactants
* used for controlled, sustained, or targeted delivery, enzyme immobilization, taste masking, and other applications
| w/o/w, o/w/o
MULTIPLE EMULSION
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* a system of **water**, **oil**, and **amphiphile**, which is a **single optically isotropic** and **thermodynamically stable** liquid solution
* almost appear **transparent** or **clear**
microemulsions
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**microemulsions** are also known as
micellar emulsions
67
* **kinetically stable liquid-in-liquid dispersions** with **droplet sizes** on the order of 100nm
* their small size leads to useful properties such as high surface area per unit volume, robust stability, optically transparent appearance, and tunable rheology
nanoemulsions
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# Method of determining the type of emulsion
a small quantity of **water-soluble dye** such as methylene blue or amaranth may be mixed with the emulsion
dye test
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# Method of determining the type of emulsion
involves **diluting** the emulsion with **either water or oil**
dilution test
70
# Method of determining the type of emulsion
uses a **pair of electrodes** connected to an external eletcric source and immersed in the emulsion
conductivity test
71
# Advantages of Pharmaceutical Emulsions
a **convenient** means of orally-administering **water-insoluble** liquids.
(e.g. fat-soluble vitamins)
O/W emulsions
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# Advantages of Pharmaceutical Emulsions
spread easily, water-washable, less-greasy and non-staining
creams & lotions
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**random movement** of particles **suspended** in fluids
brownian
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The process where the particles **adhere by stronger forces in compacted cake** (**worse** than flocculation).
aggregation
75
**Growth** and **fusing together of crystals** in the precipitate to **produce a solid aggregate**
caking
76
* **Counteracts sedimentation** of particles with a diameter of about 2 to 5 micrometers
* The **dispersed material** is kept in **random motion**.
* It is **not present** in pharmaceutical suspensions that **has suspending agents** – is **eliminated** when the sample has **50% glycerin** (5 centipoise)
* Only happens in** diluted suspensions**
brownian movement
77
* Known as **shear-thinning systems**
* Viscosity of a pseudoplastic substance **decreases** with **increasing rate of shear**.
* **Shaking** or **agitation** **decreases viscosity**
pseudoplastic flow
78
* Known as **Bingham bodies**
* Does **not begin to flow** until shearing stress corresponding to the yield value is **exceeded**
* Applicable to **semisolids**
* **It will only start to flow after reaching the yield value**
plastic flow
79
* An **isothermal** and **comparative slow recovery**, on standing of a material, of a **consistency lost through shearing**.
* **Gradually** becomes **viscous** if there is **no agitation**
Thixotropy
80
Characterized by the **absence of coalescence** of the internal phase, **absence of creaming**, and **maintenance of elegance** with respect to **appearance**, **color**, **odor**, and other physical properties
stable emulsion
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An **agglomeration** of the internal phase and its **separation** from the product.
unstable emulsion
82
**Results from flocculation** and concentration of globules of the internal phase but **does not necessarily lead to instability** however,
o It **represents** potential steps towards **complete coalescence** of the internal phase.
o May result in a **lack of uniformity** of drug distribution and unless thoroughly shaken before administration leads to variable dosage.
o Affects the **visual appeal** of an emulsion
creaming
