Design and Calibration of a
Dissolution Test Equipment
Training Workshop on Dissolution,
Pharmaceutical Product Interchangeability
and Biopharmaceutical Classification System.
Kyiv, Ukraine, June 25 - 27 2007
Dr. Sandra Klein, Institute of Pharmaceutical Technology,
Johann Wolfgang Goethe University Frankfurt
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Dr. Sandra Klein, 06/2007
Dosage forms to be tested
• immediate release dosage forms
• powders, granules / beads, tablets, capsules
• controlled release dosage forms
• powders, granules / beads, tablets, capsules
• transdermal systems
• implants
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Dr. Sandra Klein, 06/2007
Official Dissolution Monographs
United States Pharmacopeia
• USP XXX (30)
European Pharmacopoeia
• Ph. Eur. 5th Edition, Supplement 5.3
British Pharmacopoeia
• BP 2007
Japanese Pharmacopoeia
• JP XIV (14)
• http://jpdb.nihs.go.jp/jp14e/contents.html
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Dr. Sandra Klein, 06/2007
Official dissolution apparatus
USP 30 classification
1. Rotating Basket (Ph.Eur./BP/JP)
2. Paddle (Ph.Eur./BP/JP)
3. Reciprocating Cylinder (Ph.Eur.)
4. Flow Through Cell (Ph.Eur./BP/JP)
5. Paddle Over Disk (Ph.Eur.)
6. Rotating Cylinder (Ph.Eur.)
7. Reciprocating Holder
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Dr. Sandra Klein, 06/2007
Which type of dissolution apparatus ?
Depends on intention
1. Quality control
• examining batch homogeneity
• examining batch to batch conformity
• examining stability
2. Research & Development
• examining drug release behavior of preformulations
• in vitro simulation of the gastrointestinal passage
3. IVIVC
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Dr. Sandra Klein, 06/2007
Apparatus 1 - Basket
Useful for
•
•
•
•
•
capsules
beads
delayed release / enteric
coated dosage forms
floating dosage forms
surfactants in media
Standard volume
•
•
6
900/1000 ml
1, 2, 4 liter vessels
Dr. Sandra Klein, 06/2007
Apparatus 1 - Basket
Advantages
•
breadth of experience
(more than 200 monographs)
•
full pH change during the test
•
can be easily automated
which is important for routine
investigations
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Dr. Sandra Klein, 06/2007
Apparatus 1 - Basket
Disadvantages
•
disintegration-dissolution
interaction
•
hydrodynamic „dead zone“
under the basket
degassing is particularly
important
•
8
limited volume 
sink conditions for poorly
soluble drugs ?
Dr. Sandra Klein, 06/2007
Apparatus 1 - Basket
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Dr. Sandra Klein, 06/2007
Apparatus 2 - Paddle
Useful for
•
•
•
•
tablets
capsules
beads
delayed release / enteric
coated dosage forms
Standard volume
•
900/1000 ml
Method of first choice !!!
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Dr. Sandra Klein, 06/2007
Apparatus 2 - Paddle
Advantages
•
easy to use
•
robust
•
can be easily adapted
to apparatus 5
•
long experience
•
pH change possible
•
can be easily automated
which is important for
routine investigations
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Dr. Sandra Klein, 06/2007
Apparatus 2 - Paddle
Disadvantages
•
pH/media change is often difficult
•
limited volume  sink conditions for poorly soluble drugs ?
•
hydrodynamics are complex, they vary with site of the dosage
form in the vessel (sticking,floating) and therefore may
significantly affect drug dissolution
•
„coning“
•
sinkers for floating dosage forms
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Dr. Sandra Klein, 06/2007
Sinker types
JP/ USP / Ph. Eur. 5.3 Sinker
„a small loose piece of nonreactive material such as
not more than a few turns of wire helix may be attached
to dosage units that would otherwise float …“
„…. other validated sinker devices may be used“
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Dr. Sandra Klein, 06/2007
Coning
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Dr. Sandra Klein, 06/2007
Apparatus 2 - Paddle
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Dr. Sandra Klein, 06/2007
Apparatus 3 – Reciprocating cylinder
Useful for
•
•
•
tablets
beads
controlled release formulations
Standard volume
•
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200-250 ml per station
Dr. Sandra Klein, 06/2007
Apparatus 3 – Reciprocating cylinder
Advantages
•
•
•
easy to change the pH
pH-profiles
hydrodynamics can be
directly influenced by
varying the dip rate
Disadvantages
•
•
•
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small volume (max. 250 ml)
little experience
limited data
Dr. Sandra Klein, 06/2007
Apparatus 3 – Reciprocating cylinder
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Dr. Sandra Klein, 06/2007
Apparatus 4 – Flow-Through Cell
Useful for
•
•
•
•
•
low solubility drugs
microparticulates
implants
suppositories
controlled release formulations
Variations
•
•
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open system
closed system
Dr. Sandra Klein, 06/2007
Cell types
Tablets 12 mm
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Tablets 22,6 mm
Powders / Granules
Implants
Suppositories /
Soft gelatine capsules
Dr. Sandra Klein, 06/2007
Apparatus 4 – Flow-Through Cell
Advantages
•
•
•
•
easy to change media pH
pH-profile possible
sink conditions
different modes
a) open system
b) closed system
Disadvantages
•
•
•
Deaeration necessary
high volumes of media
labor intensive
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Dr. Sandra Klein, 06/2007
Apparatus 4 – Flow-Through Cell
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Dr. Sandra Klein, 06/2007
Apparatus 5 – Paddle over disk
Useful for
•
transdermal patches
Standard volume
•
23
900 ml
Dr. Sandra Klein, 06/2007
Apparatus 5 – Paddle over disk
Advantages
•
standard equipment
(paddle) can be used, only
add a stainless steel disk
assembly
Disadvantages
•
disk assembly restricts
patch size
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Dr. Sandra Klein, 06/2007
Apparatus 6 – Rotating cylinder
USP apparatus 7 – Reciprocating holder
most probably will be
removed from the USP !!!
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Dr. Sandra Klein, 06/2007
Summary
Immediate release dosage forms:
 apparatus 1 or 2 (preferably 2)
Controlled release dosage forms:
 apparatus 1 or 2 using different media for QC
 apparatus 3 or 4 for R&D purposes
Beside the selection of an adequate dissolution apparatus,
adequate test conditions are crucial for all purposes !
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Dr. Sandra Klein, 06/2007
Qualification of Dissolution Systems
Prednisone
3
Absorption @ 242 nm
2,5
y = 0,0432x - 0,0039
2
1,5
1
0,5
0
0
10
20
30
40
50
60
Concentration [mg/L]
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Dr. Sandra Klein, 06/2007
Calibration
Why ?
•
to confirm suitability of the equipment and proper operation of
the apparatus
How ?
•
•
mechanical calibration (verification of physical parameters)
chemical calibration („Apparatus Suitability Test“ – USP)
When ?
•
•
•
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before using new test equipment
after relocation or major maintenance
at regular intervals („every 6 months“)
Dr. Sandra Klein, 06/2007
Factors that may affect reliability of the test
Proper alignment/geometry of dissolution apparatus
– dimensions of vessels, paddles, baskets, cylinders
– height, centering and wobble
Proper conditions during dissolution test
–
–
–
–
–
temperature
agitation speed
degassing
sampling (sampling zone, timing, filtration, dilution)
vibration
Proper validation of analytical method
– specified in USP Chapter <1225>
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Dr. Sandra Klein, 06/2007
Mechanical calibration
•
Verification of physical parameters specified in the
pharmacopoeia: USP apparatus 1 and 2
Calibration parameter
Current USP tolerance
Point of measuring
Height
25 + 2 mm
paddle/basket bottom
Basket wobble
+ 1 mm as runout
bottom of basket
Rotational speed
+4%
not applicable
Vessel/shaft centering
+ 2 mm from center line
center line
Vessel temperature
37 + 0.5 °C
not applicable
Bath levelness
level
base plate
Shaft/paddle wobble
+ 1 mm as runout
above top of paddle
Paddle/basket dimensions
see USP
see USP
Vessel dimensions
see USP
see USP
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Dr. Sandra Klein, 06/2007
Mechanical calibration - Parameters
Height – Vertical Position of the Paddle or Basket
– the vertical position of paddle or basket affects the
hydrodynamics condition in the vessel
– each paddle or basket should be individually adjusted to the
compendial distance
– in the pharmacopoeia, a distance of 2.5 + 0.2 cm
is specified
– different kinds of height gauges can be used
to align or check* this parameter
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*
Dr. Sandra Klein, 06/2007
Mechanical calibration - Parameters
Rotational Speed – Stirring Rate
– input variable that affects the hydrodynamics
– changes in the rotational speed result in a changing liquid-solid
interface between the solvent and the dosage form
– the rotational speed can be checked by using a
digital tachometer*
*
– the compendia specify a rotational speed
tolerance of + 4 %
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Dr. Sandra Klein, 06/2007
Mechanical calibration - Parameters
Shaft Wobble – Eccentricity of Stirring Device
– assumed to alter the pattern of fluid movement in both paddle
and basket apparatus and therefore may influence the
dissolution rate
– can be measured with a micrometer*
– measured is the sum of distance between both
sides (180°) of the axis of rotation
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*
Dr. Sandra Klein, 06/2007
Mechanical calibration - Parameters
Centering (Vessel / Shaft)
– the axis of the rotating shaft must coincide at all
points with the axis of the vessel to within + 1 mm
– “the shaft has to positioned so that is axis is not
more than 2^mm at any point from the vertical axis
of the vessel and rotates smoothly without
significant wobble”
*
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Dr. Sandra Klein, 06/2007
Mechanical calibration
Measurement tools
• all mechanical tools used for
calibration should be certified
to assure their reliability
• the results of mechanical
calibration have to be documented
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Dr. Sandra Klein, 06/2007
Apparatus suitability test (USP)
• if all parts ( apparatus, geometry, test conditions, analytical
method) are within compliance – why perform an apparatus
suitability test?
• the apparatus suitability is to check for parameters that can not be
conveniently measured (vibration, vessel cleanliness, medium
degassing ...) and also to provide an overall check of the system
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Dr. Sandra Klein, 06/2007
Apparatus suitability test (USP)
• first established in 1978
• routine test in most pharmaceutical laboratories
• calibration at regular intervals (every 6 months)
• standard calibrator substances according USP chapter <711>
• only the method(s) to be used have to be calibrated !
• if six units are tested – all have to pass
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Dr. Sandra Klein, 06/2007
Apparatus suitability test (USP)
Standard calibrators according to USP chapter <711>
Apparatus I, II and V:
1. disintegrating type
–
USP Prednisone Tablets
2. nondisintegrating type
–
USP Salicylic acid Tablets
Apparatus III:
•
USP Chlorpheniramine Maleate Extended-Release Tablets
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Dr. Sandra Klein, 06/2007
Information supplied with calibrators
http:/www.usp.org/referenceStandards/useAndstorage/calibrators.html
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Dr. Sandra Klein, 06/2007
Apparatus suitability test (USP)
USP Prednisone Tablets RS – current lot P0E203
(10 mg nominal prednisone content per tablet)
•
disintegrating type
•
paddle and basket, 50 rpm
•
500 ml deaerated water, 37°C
•
quantity of prednisone released after 30 minutes is determined
•
specified ranges Lot P0E203: Apparatus 1:
Apparatus 2:
40
47-82 %
37-70 %
Dr. Sandra Klein, 06/2007
Apparatus suitability test (USP)
USP Salicylic acid Tablets RS – current lot Q0D200
(300 mg nominal salicylic acid content per tablet)
•
nondisintegrating type
•
paddle and basket, 100 rpm
•
900 ml deaerated phosphate buffer, 37°C
•
quantity of salicylic acid, released after 30 minutes is determined
•
specified ranges Lot Q0D200:
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Apparatus 1:
Apparatus 2:
23-30 %
17-25 %
Dr. Sandra Klein, 06/2007
Apparatus suitability test (USP)
Controversies regarding the current test
•
the variability in the intrinsic performance of the USP calibrator
tablets is so great that it exceeds the variability in intrinsic
performance of modern test dissolution assemblies
•
this variability becomes obvious in both vessel-to-vessel
variability and inter-laboratory variability of results for a given lot
of calibrators
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Dr. Sandra Klein, 06/2007
Troubleshooting
Calibrator Tablets:
• always check the incoming tablets !
• right lot of calibrators ?
• are the tablets broken, fused or severely chipped ?
• particularly salicylic acid tablets are often subject to sublimation
( dust on the tablets and the inner surface of the container)
• use correct storage conditions !
• take the tablets out of the original
container immediately before test !
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Dr. Sandra Klein, 06/2007
Troubleshooting
Standard / Standard solution:
• USP Standard used ?
• drying procedure conducted ?
• standard solution prepared on day of test ?
• standard solution filtered in the same manner as sample ?
• amount of alcohol used in the standard < 5% ?
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Dr. Sandra Klein, 06/2007
Troubleshooting
Vibration
• vibration produces unwanted variation in dissolution data and
mostly results in an increased dissolution rate
• internal vibration may be caused e.g. from frayed drive belts
• external vibration may be caused by e.g. magnetic stirrers,
centrifuges, vacuum pumps, old fridges, nearby construction, ...
• inability to properly measure vibration levels at various points
within an apparatus is the main reason why calibrator tablets were
originally developed
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Dr. Sandra Klein, 06/2007
Troubleshooting
Vibration effects – case example:
Kaniwa N. et al. (1998)
Int J Pharm, 175, 119-129
„Low vibration“: < 0.05 m/s2
„High vibration“: > 0.05 m/s2
Effect of vibration levels of the dissolution apparatus on the dissolution rate of enteric
coated granules of Cefalexin. The vertical dotted line indicates 0.05 m/s2.
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Dr. Sandra Klein, 06/2007
Troubleshooting
Vibration:
• dissolution equipment placed planar ?
• drive chain or belt free of tension and/or dirt ?
• torn parts replaced ?
• correctly functioning gear plates ?
• individual spindles are not surging ?
• bench/table stable ?
• no sources of vibration nearby ?
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Dr. Sandra Klein, 06/2007
Troubleshooting
Dissolution medium:
• correctly degassed ?
• correct amount used (900/500 ml) ?
• correct amount dosed (weight/volume) ?
• dosing procedure gentle (resaturation/spillage) ?
• buffer correct (pH + 0.05 units, buffer salts, molarity) ?
• correct temperature during test (32°C / 37°C + 0.5°C)?
• evaporation during test negligible ?
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Dr. Sandra Klein, 06/2007
Troubleshooting
Importance of degassing:
• insufficient degassing may result in decreased dissolution rates of
several drugs
• e.g. prednisone tablets but also a range of poorly soluble drugs are
very sensitive to the amount of dissolved gases in the dissolution
medium
• the degassing procedure should therefore be efficient and
reproducible for every test
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Dr. Sandra Klein, 06/2007
Troubleshooting
Deaeration method USP
• heat the dissolution medium to about 41°C
• vacuum filter through a 0.45-µm-porosity membrane into a flask,
stirring with a magnetic stirrer
• continue to draw a vacuum and stir for an additional 5 min
• gently transfer the medium directly into the vessel
• rotating the apparatus 2 shafts to speed equilibration to 37°C is
discouraged!!!
• use medium promptly after equilibration
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Dr. Sandra Klein, 06/2007
Troubleshooting
Alternative deaeration methods
• the USP states that „other validated deaeration techniques for
removal of dissolved gases may be used“
• other techniques include:
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
heating

sonication

vacuum

helium sparging (expensive)
Dr. Sandra Klein, 06/2007
Troubleshooting
Sampling
• take each sample at the correct time point
 sampling time points (+ 2%)
• use a single glass syringe for each vessel
• sample from the right location within the vessel
 between media surface and top of the
paddle blade
 n.l.t. 10 mm from vessel wall
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Dr. Sandra Klein, 06/2007
Troubleshooting
Sampling
• always use a suitable filter  check filter adsorption
• check the clearity of the filtered sample
• filter the sample immediately after sampling
• for automated sampling also check the tubings
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Dr. Sandra Klein, 06/2007
Troubleshooting
Physical conditions of the apparatus
• vessels scrupulously clean ?
• vessel surface smooth and curvature appropriate ?
Apparatus 1
• the conditions of the baskets, particularly of their clips is critical
• check all baskets for corrosion and blocked meshes before using
them
• align the air holes to prevent air cushions emerging during the test
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Dr. Sandra Klein, 06/2007
(Semi) Automation
Advantages
• high throughput of samples
• minimizes analyst-to-analyst variability in sampling and filtration
• reduces the average costs per analysis
• very promising for QC purposes
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Dr. Sandra Klein, 06/2007
Media preparation
• automated mixing of water
and concentrate
• preheating of medium
• deaeration
(vacuum and stirring)
• media can be dispensed
directly into the vessel
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Dr. Sandra Klein, 06/2007
Offline system
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Dr. Sandra Klein, 06/2007
Online system
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Dr. Sandra Klein, 06/2007
On- / Offline system
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Dr. Sandra Klein, 06/2007
HPLC - online system
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Dr. Sandra Klein, 06/2007
Automation
•
always validate automated methods, including analytical and
sampling methods
•
validation should be performed using manual analysis,
withdrawing samples at the same times and comparing to the
automated results:
 not highly variable dissolution results: two concurrent runs
 highly variable dissolution results: simultaneous sampling
•
pay attention to automated dilution and filtering processes
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Dr. Sandra Klein, 06/2007
Suggested reading
•
FIP Guidelines for dissolution testing of solid oral products.
Dissolution Technologies 4:5-14 (1997).
•
SM Diebold, JB Dressman. Dissolved oxygen as a measure for de- and re-aeration of aqueous
media for dissolution testing.
Dissolution Technologies 5: 13-16 (1998).
•
S Qureshi. Calibration – the USP dissolution apparatus suitability test.
Drug Inf. J. 30, 1055-1061 (1996).
•
N Kaniwa et al. Collaborative study on the development of a standard for evaluation of vibration
levels for dissolution apparatus.
Int. J. Pharm. 175: 119-129 (1998).
•
VA Gray, CK, Brown, JB Dressman, LJ Leeson. A new general information chapter on dissolution.
Pharmacopoeial Forum 27 (6) [Nov.-Dec. 2001]
•
W Brown. General information <1092> The dissolution procedure: development and validation
Pharmacopoeial Forum 30 (1) [Jan.-Feb. 2004]
Of general interest:
•
Dissolution Technologies: http://www.dissolutiontech.com
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Dr. Sandra Klein, 06/2007
Dr. Sandra Klein
Johann Wolfgang Goethe University
Institute of Pharmaceutical Technology
9 Max von Laue Street
Frankfurt, 60438, Germany
e-mail: Sandra.Klein@em.uni-frankfurt.de
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Dr. Sandra Klein, 06/2007