The particle size of a drug can affect its release from dosage forms that are administered orally, parenterally, rectally and topically.

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2. MICROMERITICS & ITS
APPLICATION IN PHARMACY
Physical Pharmacy
FAIZAN AKRAM
M.PHIL. SCHOLAR (PHARMACEUTICAL SCIENCES)
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3. TABLE OF CONTENTS
1. INTRODUCTION
2. PARTICLE SIZE AND SIZE DISTRIBUTION
3. RANGE OF PARTICLE SIZES
4. METHODS FOR DETERMINING PARTICLE SIZE
5. MICROMERITICS APPLICATIONS
6. IMPORTANCE OF MICROMERETICS IN PHARMACY
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4. INTRODUCTION
• Micromeritics is the study of fundamental and derived
properties of individual as well as a collection of particles and
thus can be called the science and technology of small
particles.
• The particle size of a drug can affect its release from dosage
forms that are administered orally, parenterally, rectally and
topically.
• In the area of tablet and capsule manufacture, control of the
particle size is essential in achieving the necessary flow
properties and proper mixing of granules and powders.
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5. PARTICLE SIZE AND
SIZE DISTRIBUTION
 Particle Size
• In a collection of particles of more than one size, two
properties are important, namely.
1. The shape and surface are of the individual particles.
2. The particle size and size distributions (The size range
and number or weight of particles).
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6. PARTICLE SIZE AND
SIZE DISTRIBUTION
 Size Distribution
• When the number or weight of particles lying within a
certain size range is plotted against the size range or
mean particle size, a so-called frequency distribution
curve is obtained.
• This is important because it is possible to have two
samples with the same average diameter but different
distributions.
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7. RANGE OF PARTICLE SIZES
• A guide to range of particle sizes applicable to each method
is.
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8. METHODS FOR DETERMINING
PARTICLE SIZE
• Many methods available for determining particle size such as
optical microscopy, sieving, sedimentation and particle
volume measurement.
1. Optical microscopy (range: 0.2-100 μm).
2. Sieving (range: 40-9500 μm).
3. Sedimentation (range: 0.08-300 μm).
4. Particle volume measurement (range: 0.5-300 μm).
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9. 1. OPTICAL MICROSCOPY
(range: 0.2-100 μm)
• The microscope eyepiece is fitted with a micrometer by
which the size of the particles may be estimated.
• A dilute suspension of the powder whose particle sizes are to
be determined is suspended in a vehicle in which it is
insoluble. A drop of the suspension is mounted on a slide or
and observed under a microscope.
• The data may be scientifically represented as a size-
frequency distribution curve. From the data the average
particle size as well as distribution is determined.
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10. 1. OPTICAL MICROSCOPY
(Advantages and Disadvantages)
Advantages:
• Agglomerates (clusters) (clumps) as well as particles of more
than one component can be detected.
Disadvantages:
• Include the fact that the measured diameter represents 2
dimensions only. The method tends to be slow and tedious
since at least 300 to 500 particles should be counted to get a
reliable data..
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11. 2. SIEVING
(range: 40-9500 μm)
• Standard size sieves are available to cover a wide range of
size.
• These sieves are designed to sit in a stack so that material
falls through smaller and smaller meshes until it reaches a
mesh which is too fine for it to pass through.
• The stack of sieves is mechanically shaken to promote the
passage of the solids.
• The result achieved will depend on the duration of the
agitation and the manner of the agitation.
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12. 2. SIEVING
Classification of powder on the basis of sieve
no:
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13. 3. SEDIMENTATION
(range: 0.08-300 μm)
• By measuring the terminal settling velocity of particles
through a liquid medium in a gravitational centrifugal
environment using Andreasen apparatus.
• The apparatus consists of 200 mm graduated cylinder which
can hold a 500 ml of suspension fluid. A stoppered cylindrical
vessel of about 5.5 cm internal diameter with a vertical scale
graduated from 0 to 20 cm on it. The stopper has an integral
10 ml bulb pipette fitted with a 2 way stop cock and a side
tube for discharging the sample. The stem of the pipette is
made of narrow bore tubing in order to retain as little of
sample as possible.
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14. 3. SEDIMENTATION
Advantages and Disadvantages
Advantages:
• The apparatus is inexpensive and the technique simple
• The results obtained are precise provided the technique is
standardized.
Disadvantages:
• The method is laborious since separate analysis is required
for each point on distribution curve.
• Very small particles can not be determined accurately since
their settling is unduly prolonged and is subject to
interference due to convection, diffusion, and Brownian
movement
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15. 4. PARTICLE VOLUME MEASUREMENT
(range: 0.5-300 μm)
• In this type of machine the powder is suspended in an
electrolyte solution.
• This suspension is then made to flow through a short
insulated capillary section between two electrodes and the
resistance of the system is measured.
• When a particle passes through the capillary there is a
momentary peak in the resistance, the amplitude of the peak
is proportional to the particle size.
• Counting is done by a computer.
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16. 4. PARTICLE VOLUME MEASUREMENT
(range: 0.5-300 μm)
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17. Micromeritics Applications
1. Release and dissolution
2. Absorption and drug action
3. Physical stability
4. Dose uniformity
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18. Micromeritics Applications
1. Release and dissolution
• Particle size and surface area influence the release of a
drug from a dosage form.
• Higher surface area allows intimate contact of the drug
with the dissolution fluids in vivo and increases the drug
solubility and dissolution.
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19. Micromeritics Applications
2. Absorption and drug action
• Particle size and surface area influence the drug
absorption and subsequently the therapeutic action.
• Higher the dissolution, faster the absorption and hence
quicker and greater the drug action
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20. Micromeritics Applications
3. Physical stability
• The particle size in a formulation influences the physical
stability of the suspensions and emulsions.
• Smaller the size of the particle, better the physical
stability of the dosage form.
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21. Micromeritics Applications
4. Dose uniformity
• Good flow properties of granules and powders are
important in the manufacturing of tablets and capsules.
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22. IMPORTANCE OF MICROMERETICS
IN PHARMACY
• The physical properties of powders such as bulk density and
compressibility are dependent on the particle size and size
distribution.
• The rate of dissolution of poorly soluble drugs is directly
related to the size of the drug particles. In general, a decrease
in the particle size of the drug increases the dissolution rate.
• Properties of drugs such as rate of absorption and hence the
pharmacological activity depends on the particle size.
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23. IMPORTANCE OF MICROMERETICS
IN PHARMACY
• Elegance of pharmaceutical preparations such as emulsions,
suspensions, ointments often depend upon the particle size
of the dispersed phase.
• The release characteristics of drugs from ointments, creams
and suppositories are dependent on the particle size of the
dispersed drug.
• Particle size of the dispersed drug also influences the
spreadability and performance of some cosmetic
preparations like dusting powders.
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