What is the criteria for linearity lower level selection for Assay and Dissolution methods
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For dissolution, the linearity lower level starts from LOQ level as the release of the drug will be lower in first time points .
For controlled release formulations, it may be 0-5% with respect to time point, so the linearity of dissolution will be starting from LOQ level in general.
For Assay, we start linearity level from 80%, as this will be the bracket ing window of the specification, in general which is 95% to 105% or 90% to 110%.
However, the range will also shows us that the product wider linear range
When we are selecting for fixing linearity for Assay, UOD also shall be taken into consideration.
The linearity levels should cover the lower and higher level strength concentrations of UOD. Thereby, we could prove linearity of the method in single time that will be applicable for both the Assay and UOD