Dissolution Failure
Investigation
Ken Boda
Dissolution Applications
Engineer

Dissolution Failure Investigation
Whenever a dissolution test fails to meet specifications, an investigation should be performed to determine the cause(s) of the failure.
Failure can be due to:
•Man (analyst)
•Machine (dissolution apparatus)
•Method (SOPs)
•Materials (standards, buffers, dosage form, etc.)

Conducting an Investigation
Investigations should be performed in a sequential process to ensure all potential sources of error are investigated
•Review data as a whole
•Perform investigation in reverse chronological order

Aerial View of the Data
The Error itself can help narrow the focus of the investigation:
•Entire data set trending high/low
•1 outlier
•High %CV
•Data which makes no sense

Data trending high/low
•Bad lot
•Calculation Error
•Standard Prep Error
•Improper Filtration
•System misalignment (overall)
•Poor evaporation control
120
100
80
60
40
20
0
1 2 3 4 5 6

1 Outlier
•Misalignment/Bad Component in
Single Position
•Filter fell off
•Bad sample reading
•Transcription Error
•Bad individual dosage form
•Contamination
•Wrong volume poured
60
40
20
0
120
100
80
1 2 3 4 5 6

High % CV
•Sampling Inconsistencies
•Poor techniques
•Vibration
•Improper Degassing
•System Misalignment (tends to trend)
•Issues w/ formulation
60
40
20
0
120
100
80
1 2 3 4 5 6

Data that doesn’t make sense
•Filtration Issues
•Bad Sample Readings
•Air bubble
•Contamination
60
40
20
0
120
100
80
1 2 3 4 5 6

Determinant vs. Non-Determinant Errors
Determinant Errors are known and controllable
Determinant errors when found will lead to a simpler investigation and require the least re-work
Indeterminate errors are unknown, suspected, or beyond control
Indeterminate errors cannot be proven, and the burden of retesting is often higher

Investigating in Reverse
•Last thing done, first investigated
•Limits scope of investigation, if determinant error found – can stop
•Last things done can often allow salvaging of the run
•All samples/standards/etc. should be kept until results have been checked and approved or fully investigated

Investigation Track
•Calculations
•Analysis
•Sampling and Filtration
•Run Observations
•Media Prep and Sample Handling
•Pre-Run Checks
•Dissolution Unit Mechanicals
•SOP and Materials

Checking Calculation Errors
•Check for transcription errors
•Are the right values being used for:
–Standard Conc.
–Label Claim
–Dissolution Volume
•Verify calculations by hand
•Ensure proper calculations are being used

Calculations without Media Replacement
T1 % Dissolved = ((((A1 x V) /As) x C) / W) x 100
T2 % Dissolved = (((((A2 x (V - R)) + (A1 x R)) /As) x C) / W) x 100
T3 % Dissolved = (((((A3 x (V
– (R x n))) + ((A1 + A2) x R)) /As) x C) / W) x 100
Where,
A1 = the absorbance of the first sample pull
A2 = the absorbance of the second sample pull
An = the absorbance of the nth sample pull
As = the average absorbance of the standard
V = the initial media volume, ml
C = the concentration of the standard, mg/ml
W = the weight of the active, mg (label claim)
R = the volume of media being withdrawn for a single sample pull, ml n = the number of the sample pull taken

Calculations with Media Replacement
T1 % Dissolved = ((((A1 x V) /As) x C) / W) x 100
T2 % Dissolved = (((((A2 x V) + (A1 x R)) /As) x C) / W) x 100
T3 % Dissolved = (((((A3 x V) + ((A1 + A2) x R)) /As) x C) / W) x 100
Where,
A1 = the absorbance of the first sample pull
A2 = the absorbance of the second sample pull
An = the absorbance of the nth sample pull
As = the average absorbance of the standard
V = the initial media volume, ml
C = the concentration of the standard, mg/ml
W = the weight of the active, mg (label claim)
R = the volume of media being withdrawn for a single sample pull, ml n = the number of the sample pull taken

Check Original UV/HPLC readings
•Right Wavelength and/or LC conditions used?
•If sample/standard readings were on
UV, check scan if available
•If sample/standard readings were on
HPLC, review chromatogram for:
– Proper peak shape
– Non-parent peaks
– Contaminants

Reanalyze Samples/Standards
•If available, reanalyze samples in question
•Reanalyze standard
•Compare standard against a fresh standard to ensure original standard was prepared correctly
– Make sure dilutions and purity are properly factored
– Dilution error possible?

Standard Preparation
•Create new standard to compare against one used for run
•Ensure adjustments are made for moisture and purity
•Right pipet/flask used?
•Within expiration period?

Storage
•Were samples within expiration period?
•Covered?
•Stored Properly?
•Labeled?

Sampling and Filtration
Sampling and Filtration are one of the most common causes of dissolution failures:
•USP Position
•USP Timing
•Filtration

USP Sampling Area
Sampling takes practice and attention!
All samples must be withdrawn:
•½ way between top of paddle/basket and media
•No closer than 1cm from vessel wall
•Recommend not sampling within
1cm of spindle

Imagine A Donut

Sample Timing
•Must sample (and filter) within 2% of the timepoint or 15 minutes, whichever is less
•Paddles/baskets must still be stirring while sampling

Filtration
•Is the filter validated?
– Efficiency
– Leaching
– Adsorption
•When was the sample filtered?
– At time of sampling?
– Immediately after sampling?
– After time point collected?

Autosampling
Autosampling can reduce many of the errors associated with manual sampling:
•Position constant
•Timing within 2%
•Consistent pull force
•Documentation

Dissolution
Observations

Observations
Observations of the dosage form are key in order to diagnose potential issues with the dosage form.
Observations can tell why something happened, % dissolved issues can only tell you what happened.

When should you take observations?
Ideally, observations should be taken at all critical timepoints of the run
•Wetting/Dose Dumping
•Release Profile
•Complete Release/Asymptote
•Whenever sampling manually
Brand to Brand Differences in Dissolution Profiles
60
50
40
30
20
10
0
0
110
100
90
80
70
30 60 90 120 150
Time (minutes)
180 210 240 270
Brand A
Brand B
Brand C

What to look for
Initial Stages:
•Floating or Moving?
•Coning?
•Dispersion Profile?
•Dissolved Gasses?
•Cross-linking?
•Compare appearance of all dosage forms

Floating/Moving Dosage Forms
•If a dosage form is floating or moving, it adds additional sources of energy to the dosage form and increases variability
•Sinkers should be used when floating, spinning, dancing, etc. occurs
•Use validated sinker

Coning
•Cones should be loose
•Cone should be in consistent location (bottom center)
•Look for consistent behavior across vessels, any trending noticed?
•In cases of severe coning, method alteration may be needed
– Higher RPM
– Peak vessel

Dispersion Profile and Dissolved Gasses
•Are air bubbles on stirring element, vessel, dosage form?
•How are particles distributed in vessel (top, middle, and bottom)
•Are particles floating?
•Presence of air bubbles may indicate degassing method is not sufficient

Cross-linking
Cross-linking of capsule shells can result in hardened and chemically resistant shells. Very common to see in stability testing.
•Delay opening
•Trap Drug Product
•Pellicle Formation
If Cross-Linking is seen, testing with pepsin or pancreatin should be performed

Compare Results of all 6-8 Vessels
•Take observations as a complete set, just like data
•Write observations down
•Is there any atypical behavior?
•Trending of observations?

Observations During Release Profile
•Size of dosage form/particles
•Distribution of dosage form
•Consistency of the dosage forms
•Anything changed?

Observations at End of Run
•Any material left?
•Describe material
•May be beneficial to assay dosage form post-mortem in formulation development or investigation of strange data or observations

Media Preparation
•Degassing Procedure validated?
•Time of degassing vs. time of use
•Pouring Technique

Sample Handling
•When exposed to air?
•Weighed?
•Inspected?
•Where placed?
•How handled?
– Bare hands
– Gloves
– Tweezers

Instrument Checks
Pre-run checks of the instrument are always recommended.
Pre-run checks are actually required if following the FDA or ASTM
Mechanical Qualification procedure.
Recheck these same parameters in the event of a run failure

Dissolution Mechanical Qualification Standards
Prior to each dissolution test, the guidelines generally agree, requiring documentation for:
• Vessel examination
• Paddle examination
• Baskets and basket shaft examination
• Vessel medium temperature measurement
• Vibration evaluation
• Water bath (USP)
• Speed measurement on single position (USP)

Dissolution Mechanical Qualification Standards
Vessel Examination, must be free from:
• Scratches
• Cracks
• Pits
• Residue
• Surface irregularities
Centering Device, should also be:
• Complete
• Tight to Vessel Plate

Vessel Examination

Dissolution Mechanical Qualification Standards
Paddle Examination, must be free of:
• Defects
• Rusting
• Corrosion
• Peeling or loose coating
• Knicks, dents or misshapen appearance

Stainless Steel Paddles – Minor Rusting

Stainless Steel Paddles – Advanced Corrosion

Teflon Paddles – Good, Okay, and Terrible

Dissolution Mechanical Qualification Standards
Basket and Basket Shaft , must be free from:
• Defects
• Rusting
• Corrosion
• Loose wires
• Clogged mesh openings
• Dented sides or bottom
• Knicks, dents or misshapen appearance
• O-ring are not compliant; three clips required

Baskets – From New to Dead

Basket – Bad Example

Dissolution Mechanical Qualification Standards
Other Requirements:
• Vessel Temperature: The temperature of the medium inside each vessel is measured at the time of use. Media temperature must be ±0.5ºC from target.
• Vibration: There can be no significant vibration in the dissolution apparatus or medium. Possible sources of vibration are the surrounding environment, the dissolution unit itself or one of its components or an external water bath circulating heater.

Perform Mechanical Checks on System
•If no issues w/ individual components is noted, investigation of the system’s overall alignment and performance should be reviewed
•MQ tolerances, particularly height and centering can be susceptible to change
•If height/centering is out, can have major impacts on hydrodynamics

Dissolution Mechanical Qualification
Specifications and Tolerances
Parameter ICH
Harmonized
(USP, JP, EP)
25 ± 2 mm
FDA
DPA-LOP.002
ASTM
E2503-07
USP Toolkit
Ver 2.0
Basket and
Paddle Depth
Rotational
Speed
± 4% of specified rate
25 ± 2 mm
± 2 rpm of target
Shaft Wobble No significant wobble
Shaft
Verticality
≤ 1.0 mm total runout
Not measured ≤ 0.5° from vertical
(x and y 90º)
Basket Wobble ± 1 mm ≤ 1.0 mm total runout lower rim
25 ± 2 mm
(or <8%)
± 2 rpm or within 2% of target (larger)
≤ 1.0 mm total runout
Within Bubble
(x and y 90º)
≤ 1.0 mm total runout lower rim
23-27 mm
± 1 rpm of target
≤ 1.0 mm total wobble
Not measured
≤ 1.0 mm total wobble

Dissolution Mechanical Qualification
Specifications and Tolerances
Parameter
Vessel/Shaft
Centering
Vessel
Verticality
Vessel Plate
Level
Performance
Verification
Test (PVT)
ICH
Harmonized
(USP, JP, EP)
FDA
DPA-LOP.002
NMT 2 mm from center axis
≤ 1.0 mm from center line
(upper/lower)
Not Measured ≤ 1.0° from vertical (2 - 90° positions)
ASTM
E2503-07
≤ 1.0 mm from center line
(upper/lower)
≤ 1.0° from vertical (2 - 90° positions)
USP Toolkit
Ver 2.0
NMT 2.0 mm difference (4-
90°positions)
NMT 0.5° from vertical
Not Measured Not Measured
USP
Prednisone
Tablets RS
Not Measured
Not Measured Not Measured
NMT 0.5° from horizontal
USP
Prednisone
Tablets RS

SOP investigation
In the event a failure can not be diagnosed, and several failures have occurred, SOP/validation review may be needed:
•Filter choice
•Chemicals specified
•Is the method over-discriminatory?
•Was intermediate precision evaluated for:
– Chemist to chemist variability
– Manual vs. autosampling
– Resident vs. non-resident probes
– 3-clip vs. O-ring baskets?

SOP Investigation
•Carryover?
•Cleaning method established?
– Dissolution apparatus
– Sampling equipment

Investigation Conclusion
•In the event of a determinant error, failing run can be aborted and test re-run
•In the event of a non-determinant error
– Multiple runs may be needed
– Analyst re-training may be advisable

Special Thanks/Reference
“Dissolution Aberrant Data Investigation”, Bryan Crist,
Pharmaceutical Canada, March 2004, vol. 4, no. 4., pp. 7-12

Questions?
Ken.Boda@Agilent.com
919-677-6797
Dissolution.Hotline@Agilent.com
1-888-826-5351
Dissolution Discussion Group www.dissolution.com

Upcoming Events http://www.chem.agilent.com/en-US/promotions/Pages/dissoseminar.aspx