Lab 9 Flashcards by amanda kastel

name 3 ways in which powders can be used in pharmacy practice

-as powder dosage forms for topical use

-pre-packed as dosage forms for other routes

-most commonly - they are processed to manufacture other dosage forms like capsules tablets, and oral inhalations or injectable powders for reconstitution

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name 2 products that use powders as topical dosage forms

dusting powders and bulk powders

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name 2 advantages of drugs administered as powders

they are more stable than liquid dosage form

they have a short onset time (bc they dont need to disintegrate)

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name 5 disadvantages of powders

-assuring uniformity of dosage is difficult

-may be difficult to store and convey (transfer)

-some of the total volume is made up of free space (air)

-powder particles tend to cling to each other and form clusters

-not suitable for hygroscopic (able to take up moisture) and deliquiscient drugs (tend to melt)

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when is it especially difficult to ensure uniformity of dosage in the powder dosage form?

when the content of the active drug is low

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why do powder particles tend to adhere to each other to form clusters?

due to electrostatic forces or moisture

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true or false

the particle size in a powder does not have to be uniform

false - it does

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many of the technical difficulties with powders are related to what properties?

rheological/flow properties

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flowability is dependent on….

physical characteristics of the powder like surface texture, particle shape, size, size distribution, cohesiveness, particle interaction, electrostatic charge and hardness

ALSO external factors like humidity, aeration, temp, work/equipment surface

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flowability is a measure of….

a powder’s ability to flow freely

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good flowability of a powder is essential for what?

dose accuracy
when dispensing the powder from its container into other dosage forms (tablets/capsules)

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true or false

the flow properties/rheology of powders is affected by 100 or more factors

true

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as mentioned, the flow properties of powders are affected by 100 or more factors.

what is sufficient to understand the flow behavior of powders?

testing a single factor is inadequate.

testing a few factors is sufficient to understand the flow properties

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define angle of repose.
what is the symbol for it

symbol = theta

the maximum internal angle between the surface of the conical/sloping and the horizontal surface for a free flowing powder pilee

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the angle of repose is used to evaluate what?

the flow properties of the powder.

corresponds to inter-particulate friction or resistance of movement between the powder particles

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angle of repose depends on…..

density of the powder
moisture content
particle size
porosity
surface area and shape of the particles
friction/interaction between the particles

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the angle of repose ranges from….

0-90 degrees

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the HIGHER the angle of repose, the _____ the flow properties

WORSE

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true or false

a low angle of repose indicates better flow properties

true

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what is the angle of repose of free flowing solids?

what about poor flowing powders?

free flowing solids = 20 degrees or lower

poor flowing powders = 40 degrees or higher

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generally ____ particles have a low angle of repose

(small or large? give specific size)

large particles greater than 100mm

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the angle of repose _____ with increasing concentration of the poorest flowing ingredient

increases

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what was used in the lab to measure the angle or repose?

a fixed base diameter

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type of flow and powder if angle of repose is less than 25 degrees

type of flow = excellent
type of powder = non cohesive

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type of flow and powder if angle of repose is 25-30 degrees

type of flow = good type of powder = noncohesive

type of flow and powder if angle of repose is 30-40 degrees

type of flow = passable type of powder = cohesive

type of flow and powder if angle of repose is greater than 40 degrees

type of flow = very poor type of powder = very cohesive

give the formula for angle of repose

theta = tan-1 (h/r) h=height of pile r = radius of base of the pile

angle of spatula is a measure of...

the relative angle of internal friction of the powders

how is angle of spatula measured

when a spatula is inserted into a powder heap parallel to the bottom and then lifted straight up out of the material

true or false the angle of repose is always greater than the angle of spatulation

FALSE the angle of spatula is always greater than angle of repose EXCEPT for very free flowing powders

except for very free flowing powders, the angle of ____ is always higher than the angle of ____

angle of spatula is always higher than angle of repose

_______ is used as a rough estimate to determine flowability

angle of spatula

for angle of spatula, a value under ______- indicates that the powder is free flowing

under 40 degrees

a ____ powder forms a single area on the spatula whereas a ____ material forms a number of irregular angles on the blade of the spatula

free flowing forms a single material non-free flowing material forms a number of irregular angles on the blade

compressibility is a test to evaluate what? how is it done?

the flowability of the powder by comparing the poured (puffed) density and the tapped density of the powder

what is bulk density

describes the amount of entrapped air in the powder

bulk density =

mass of particles/volume of powder

what kind of powders will have the greatest difference between their tapped and aerated bulk density?

powders with significant frictional and cohesive interactions

_____ compressibility values generally indicate decreased flowability

high

true or false tapped density does not vary with the number of taps and style of tapping

false - it does

give the formula for percent compressibility

% compressibility = tapped density - bulk density / tapped density

cohesiveness describes....

the adherence of the powder particles to each other

cohesiveness is dependent on what?

the physical and chemical nature of the powder also influenced by particle size and moisture content

the ____ the moisture content in a powder, the higher the cohesiveness

higher

what is the oldest method of classifying powders by the size of the particles?

sieving

in the sieving method of classifying powders by particle size, which sieve is on top and which is on bottom?

top = coarsest bottom = finest

what USP chapter describes specific terms to define powder fineness

USP 811

Powders with ____ particles (what size?) are more likely to be non-cohesive, permeable, and have better flowability and low compressibility?

large particles (greater than 100 micrometers)

what powder size is likely to be cohesive, compressible, and contain a lot of entrapped air?

less than 10 micrometers

true or false the lower the particle size, the higher the cohesiveness

true

what describes the mesh size?

the number of openings in the mesh screen per inch

X50 is when....

50% of the particles are smaller and 50% of the particles are larger than the mess size

X90 means....

the particle size corresponds to 90% of cumulative undersize distribution

X10 means....

the particle size at which 10% cumulative undersize distribution

to classify a powder as COARSE, at least ___% of the % cumulative distribution must be greater than 355 microns (micrometers)

50%

particle size more then 250 micrometers describe flow properties

free flowing

particle size less than 10 micrometers describe flow properties

resistant to flow

particle size 10-100 micrometers describe flow properties

poor flow

how are dusting powders dispensed?

either as bulk powders or in sifted top containers

further classify dusting powders

may be medicinal or cosmetic -- intended to be applied to skin

explain medicinal dusting powders

API is mixed with a base powder. thymol and menthol may be added for cooling sensation

name 2 things that can be added to medicinal powders for a cooling sensation

thymol and menthol

name things that can be used as inert bases for dusting powders

bentonite kaolin magnesium carbonate starch talc

what do powder bases do?

absorb secretions and exert a drying effect

dusting powders should be able to pass through what sieve and why?

100-200 mesh sieve to ensure they are grit free and smooth to the touch - non irritating to the skin

___ and __ powders have the tendency to absorb moisture from the atmosphere

hygroscopic and deliquescent

give 3 examples of deliquescent powders. Are they able to fully dissolve?

can partially or fully dissolve due to the adsorbed moisture sodium chloride sodium bromide pilocarpine

name 3 strategies to avoid the adsorption of moisture by the powder dosage form

-add a hydrophilic but water insoluble powder that will adbsorb the water attracted by the hygroscopic/deliquescent material -dispense product in tightly closed container and store in low humidity area -add desiccant packets into container

what are efflorescent powders

crystalline substances containing water of crystallization or hydration

when can efflorescent powders release their water content?

under mechanical stress (like trituration) in a low humidity environment

when efflorescent powders release their water content under mechanical stress like trituration, what happens to the powder?

it becomes damp

in general what is the problem with when efflorescent powders release their water of hydration or crystallization

a given weight of powder no longer contains the same amount of drug

give 3 examples of efflorescent powders

atropine sulfate codeine sulfate morphine acetate

name 2 strategies to handle efflorescent powders

store in tight container substitute with anhydrous form of drug

what are eutetic mixtures

solids that have the tendency to liquefy when mixed with each other due to the depression of melting points of the materials -- bc one substance acts as an impurity for the other substance

when does the handling of eutetic mixtures pose a problem

when the melting point of the powder mixture is near or below room temp. result is a paste or a liquid

give example of eutetic mixture and their melting point

camphor (mp = 180 degrees c) menthol (mp = 42 degrees c)

how to handle eutetic mixture if: -amount of eutetic mixture is small in the powder -amount of eutetic liquid is large

if smol - the liquid can be adsorbed onto a diluent or other powder in the formulation if large quantity - eutetic components should be mixed separately with equal amounts of the other powder ingredients -- helps to avoid physical contact between the eutetic components

what is calamine

a mixture of zinc oxide with about 0.5% ferric oxide or a zinc carbonate anti itch that works via cooling sensation as it evaporates on the skin

explain what calamine is used for

for mild pruritic conditions like sunburn, eczema, rashes also dries oozing or weeping from minor skin irritation

historically, what has calamine been used as

mixed with rose water to create soothing face mask used in face powders, dusting powders (adsorbent), and toothpastes

explain what talc is and why it's used

a natural product that contains basic magnesium silicate has sopay feeling with gives smooth tecture useful excipient as diluent, filler, bulking agent, lubricant, glidant, adbsorbent, opacifying agent, skin protectant

what is magnesium stearate primarily used as

a glidant/lubricant in the manufacture of powders, capsules, and tablets

why is a glidant/lubricant like magnesium stearate used

to reduce friction between moving surfaces and improve FLOW

what concentrations is magnesium stearate effective

only 0.5%-1% ineffective at higher conc