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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5320_Библиотеки_им_академика_М_И_Перельмана
.pdf
x
m
kP
n
+
kP
kP
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336
19.3.2 Surface Area
19.3.2.1 Significance of Surface Area
Pharmaceutical Dosage Forms and Drug Delivery
• Absorption of a drug from a dosage form involves the dissolution of the drug substance into the
•
-
face coverage and effectiveness of the lubricant.
•
granulation.
19.3.2.2 Defining Surface Area
-
gration and drug dissolution from granules depends on the penetration of the dissolution medium inside
practical purposes, this distinction is ignored. It is assumed that the surface area accessible to the penetrating
19.3.2.3 Quantitation of Surface Area by Gas Adsorption
-
tial pressure of the gas (P). At isothermal (constant temperature) conditions, Freundlich proposed that the
mass of gas adsorbed (x) per unit mass of adsorbent (m
= */1
k and n are constants.
an alternative equation to describe gas adsorption on the solid surface that relies on the assumption of
θ
*
=
*1
k ka/ kd, ka, and kd representing the rate constants of adsorption and desorption processes,
P
+−
00
EE
=
−
1L
11
P
C
mm
−
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Powders and Granules
337
WC
**
C
P
0
PPP
P
0
is the total
total
total
=
m
P
−
**
11
P
P and P0 are the equilibrium and saturated vapor pressure of the adsorbate; W
amount of gas adsorbed; WmC
E1), the heat of adsorption for the second and
E), gas constant (R), and absolute tem-
perature (T) as
RT
θ
total
1
=
P
0
−
1
*
WCPPW C
+
*
0
*
W
) as a function of the
total
equilibrium pressure (P
Wm
2
19.3.2.4 Altering Powder Surface Area
surface area of the material.
plate
surface area.
BD
−
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338
Pharmaceutical Dosage Forms and Drug Delivery
processing equipment during pharmaceutical manufacture is a function of the surface characteristics
19.3.3 Density and Porosity
19.3.3.1 Significance of Density Determination
19.3.3.2 Defining Powder Density
• Bulk density loosely
• Tapped density
TD BD
=
TD
=
BD
PVnRT=
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Powders and Granules
339
• True density solid
19.3.3.3 Methods for Quantifying Powder Density and Porosity
laboratories.
•
P is the pressure; V is the volume; n is the mole of gas; R is the gas constant; and T is the
temperature.
•
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340
19.3.3.4 Changing Powder Density and Porosity
Pharmaceutical Dosage Forms and Drug Delivery
changed during several pharmaceutical unit operations.
19.3.4 Flow
opening of a funnel.
19.3.4.1 Importance of Flowability of Powders
•
•
•
•
19.3.4.2 Factors Influencing Flow of Powders
•
•
such as a hopper.
•
bed of coarse particles.
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Powders and Granules
341
19.3.4.3 Quantitation of Powder Flow
repose is indicative of the ease of particles sliding across each other and is interpreted to indicate a better
19.3.4.4 Manipulation of Flow Properties of Powders
19.3.5 Compactibility
19.3.5.1 Compressibility, Compactability, and Tabletability
As illustrated in Figure 19.2
•
FIGURE 19.2
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342
Pharmaceutical Dosage Forms and Drug Delivery
•
•
compact (tensile strength) as a function of the compaction pressure used.
19.3.5.2 Importance of Compactability
consolidated state under pressure.
19.3.5.3 Determination of Compaction Characteristics
tableting equipment, such as Presster®
movement during compression).
19.3.5.4 Factors Affecting Compactability
19.3.6 Content Uniformity
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Powders and Granules
343
19.3.6.1 Importance of Uniform Mixing
19.3.6.2 Factors Affecting Mixing Uniformity
•
•
often sandwiched
•
blender.
•
potential of particles of different components.
19.3.6.3 Assessment of Content Uniformity
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344
Pharmaceutical Dosage Forms and Drug Delivery
19.3.6.4 Addressing Content Nonuniformity Issues
19.4 Powder Processing
19.4.1 Increasing Particle Size: Granulation
•
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Powders and Granules
•
19.4.1.1 Dry Granulation
Figure 19.3
19.4.1.2 Wet Granulation
-
tion form.
•
are complete, the granulation is force passed through an appropriate screen, using equipment such
FIGURE 19.3 Am. Pharm. Rev
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