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Accuracy
• Prepare at least 6 replicate spiked solutions at the 100% level or 3 replicates at multiple (minimum 3) concentration levels. • Transfer to the dissolution vessel and heat to 37°C. • Collect either three solutions over the course of the dissolution test or three solutions at the final time point.
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Precision
• Repeatability
– Is determined on standards for the analytical method alone
• Intermediate precision
– Different analysts – Different equipment – Different days – Bracketing accepted
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Validation of the analytical method
• Placebo effect is allowed [up to 2% USP]
• No impurities need to be considered
– Any impurities >1% are below the accuracy of the dissolution test itself – However the stability of the active itself must be demonstrated
Validation
The analytical method
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USP <1092> The dissolution procedure: Development and Validation
General comments
“The dissolution procedure requires an apparatus, a dissolution medium and test conditions that provide a method that is discriminating yet sufficiently rugged and reproducible for day to day operation and capable of being transferred between laboratories”
– Withdraw and filter samples per method.
• Calculate the % recovery
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Why determine recovery?
• Dissolution is a use test and there should be no requirement for this determination • There are products which release at best 25% [medicated chewing gums]
No interference No interference
No major problem Interferes with column at high concentration Interferes with column and sometimes incompatible with mobile phase
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Choice of the analytical method
• UV is always preferred over HPLC
• Remember you may use a UV cell with greater than 1cm path length
• UV is unlikely to be suitable when:– The compound has no or low wavelength maxima – The drug contains more than one active – The concentration is very low [1mg or less] – The media interferes
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Filtration
• Usually necessary to prevent undissolved drug or excipients entering the analytical sample otherwise there maybe:– Continued solution
– Clogging HPLC columns
– For the assay of a drug product normally from 80 to 120% of the test concentration
– For content uniformity 70 to 130%
– For dissolution testing +/-20% over the specified range e.g. if the specifications for a controlled released product cover a region from 20% after 1 hour up to 90% after 24 hours, the validated range would be 0-110% of label claim Typically r2>0.98 demonstrates linearity and the y-intercept should be close to zero
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Analytical validation ICH Q2(R1)
Dissolution Assay Procedure
PARAMETER ACCURACY EARLY DEVELOPMENT What is this? FINAL PROCEDURE YES
3. ACCURACY PRECISION The accuracy of an analytical procedure expresses the closeness Yes of agreement Repeatability Yes between the value which is accepted either as a conventional true value or an Interim precision No Yes accepted reference value and the value found. This is sometimes termed trueness. No Reproducibility Yes
DO NOT CENTRIFUGE
The drug substance will continue to dissolve in the solution after sampling giving an artificially high result
Trapped drug particles retained on filter can give anomalous results
• …..typically 95-105% of the amount added
Prepare a solution of the drug substance in the dissolution media and transfer it to the dissolution vessel containing the excipients
– – – – – Medium composition [buffer or surfactant conc.] pH Volume Agitation rate Temperature Is this for real?
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Significant effects
• Paddle height (+ 0.5 cm)
– Lower or higher may effect cone
• Bath temperature (+ 1 degree)
– Big factor with poorly soluble drugs
• Sample times (+ two minutes)
– Important with rapidly dissolving – ongoing dissolution in syringe
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Accuracy/Recovery
USP <1092> • Typically established by preparing samples containing the drug and excipients • …..in the case of poor drug solubility it may be appropriate to dissolve the drug substance in a small amount of organic solvent and diluting to the final concentration with dissolution medium
USP Monograph-proposed
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SAMPLING-Manual
– Turbidity anomalies in UV
• It maybe in-line, at the end of the sampling probe or both • Pore size should be appropriate for the sample