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47 Cards in this Set

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What is a powder?
a mixture of dry, finely divided drug and/or chemicals that is intended for internal or external use
What is a granule?
dry aggregates of powder particles
9 adv.s of powder?
1. flexibility of compounding

2. good chemical stability

3. rapid dispersion of ingredients

4. little or no disintegration reqd

5. rapid onset of action

6. easy to administer to elderly and children

7. can be mixed with food or liquids

8. a better choice if drug is too bulky to be prepped as tab or cap (ex. metamucil)

9. prep. as individualized doses
4 Disadv.s of powder?
1. time consuming preparation

2. inaccuracy of dose because of bulk

3. unpleasant tasting, hygroscopic and deliquescent (absorbs moisture, melts away)

4. pt. has to measure the amt taken
Powder classifications are based on what?
size
When are powders sometimes modified?
before use as a pharmaceutical component
Range of particle sizes?
from very coarse to extremely fine approaching colloidal dimension (1 micron or less)
The descriptive terms utilized by the USP to characterize particle size?
Very coarse, coarse, moderately coarse, fine, and very fine related to the proportion of powder that passes thru opening of standard sieve in a specific time while being shaken
Particle size is described in terms of what?
sieve number or mesh fraction (a large sieve number = a smaller sieve opening)
Sieve No. 8 corresponds to what particle size?
very coarse
Sieve No. 80 corresponds to what particle size?
very fine
Sieve No. 20 corresponds to what particle size?
coarse
Sieve No. 60 corresponds to what particle size?
fine
Sieve No. 40 corresponds to what particle size?
moderate
Particle size of a powder can influence what 5 things?
1. suspendibility

2. uniform distribution

3. penetrability

4. dissolution rate and bioavailability

5. lack of grittiness
Explain how particles size influences suspendability?
(suspension and solution) need uniform dispersion in liquid vehicle (1-50 microns)
Explain how particle size influences uniform distribution?
ensures dose to dose content uniformity
Describe how particle size influences penetrability of particles?
refers to the penetrability of particles for inhalation (about 5-20 microns)
Describe how part. size influences dissolution rate and bioavailability?
dissolution rate and bioavailability often depend on particle size of drug

1. reduction in particle size (micronization) can increase dissolution rate and enhance bioavailability

2. the smaller the particle size of the drug, the larger the surface area and the faster the rate of dissolution

(ie, larger SA = Greater dissolution = Greater bioavailability)
3 methods of determining particle size?
1. sieving

2. microscopy

3. sedimentation
Describe the process of sieving?
it is one of the simplest and more frequently used methods of determining particle size distribution

-involves size classification followed by the determination of the wt. of each fraction

-part.s are passed by mechanical shaking thru a series of sieves of known and successively smaller size and determination of the proportion of powder passing thru or being withheld on each sieve (range 40-9500 microns)
Particle size range for sieving?
40-9500 microns
US standard sieves available?
3&1/2 to 400 mesh (larger mesh = smaller particle size)
Descrbie the process of microscopy?
one of the most accurate and direct methods of particle size determination...particles are sized thru the use of a calibrated grid background incorporated into the microscope (range 0.2 to 100 micrometers)
Describe the process of sedimentation?
it is a method of part. size determination using ANDREASEN PIPET, a special cylindrical container from which sample can be removed from the lower portion at selected intervals....the powder is dispersed in a nonsolvent in the pipet, agitated and 20 mL samples are removed, dried and then weighed. (powder settles in solvent)
Comminution or milling refers to what?
particle size reduction
Particle size reduction on a lg scale involves the use of what?
mills
Particle size reduction on a small scale involves what?
using a mortar to triturate
List 3 methods for particle size reduction?
1. trituration

2. pulverization by intervention

3. levigation
What is trituration?
a method of particle size reduction that involves the use of a mortar and pestle to grind solid to reduce its particle size and/or mix two or more substances intimately
What is pulverization by intervention?
a method of part. size reduction...material is dissolved in a small amt of volatile solvent (alc. or ether) solution may be spread on tiles of mortar or tile. Solvent is evaporated, film of fine crystals scraped off...done to increase SA by decreasing part. size
Give two examples of pulverization by intervention?
1. iodine crystals and ether

2. camphor crystals and alcohol
What is levigation?
a method of part. size reduction...a paste is formed by the addn of a levigating agent to the solid material. The rubbing the paste in a mortar and pestle or by use of an ointment slab (the paste is triturated to decrease particle size) (the paste is then added to an oint. base and mixed in a "figure 8", to make uniform and smooth on pile tile with spatula
Give ex.s of levigating agents? (3)
1. glycerin

2. M.O.

3. propylene glycol
3 types of mortars?
1. wedgwood

2. porcelain

3. glass
Which types of mortars have a rougher surface? What does this result in?
wedgwood and porcelain...fine grinding action results in finer/smaller particles
Which of the different mortar types has a smooth surface? What does this result in?
glass...less grinding
5 types of powder blending?
1. spatulation

2. trituration

3. geometric dilution

4. sifting

5. tumbling
Describe spatulation?
a method of powder blending

1. blending sm. amts of powders by mvmt of spatula on a sheet of paper or ointment tile

2. very little compression or compacting of the powder occurs

3. not suitable for large qtys of powders

4. not suitable for powders containing potent (ex. nitroglycerin, digoxin) drug because homogenous blending is not certain

5. exp. suited for eutectic mixturs
What occurs if you keep a eutectic mixture mixed?
they liquify
Define eutectic?
solid subst.s that liquify
Give 6 examples of eutectic substances?
1. phenol

2. menthol

3. camphor

4. thymol

5. aspirin

6. phenylsalicylate
How do you solve the problem of a eutectic mixture?
first mix the eutectic solid with an inert diluent (MgO, Mg Carbonate, etc) that physically separates eutectic forming ingredients
What is trituration?
a method of powder blending...inv.s the use of a glass mortar for simple mixing...reduces particle size and blends (not very fine grinding)
What is geometric dilution?
when a small amt of potent substance is to be mixed with a large amt of diluent by trituration (either oint. or powder)(figure 8s)
What is sifting?
a method of powder blending where powders are mixed by passing powders thru sifters...this is not good for mixing potent drug incorporation
Describe tumbling?
a method of powder blending...inv.s mixing powders in a rotating chamber with the use of a motorized blender, mixing is accomplished by tumbling motion...sometimes use blending blades to help mixing...mixing is thorough but time consuming