In vitro dissolution tests are valuable in product development and to monitor batch to batch consistency of the manufacturing process following approval to market. In vitro dissolution test results are also used to test release characteristics of a dosage form in storage, i.e., to measure stability of the release rate. Dissolution testing may be considered as a useful check for several characteristics of the dosage form, to include:
- particle size distribution, state of hydration, crystal form and other solid state properties of the active ingredients;
- mechanical properties of the form itself (water content, resistance to crushing force for tablets, integrity of the shell for capsules and coated tablets, etc.).
When used in product quality control, information about in vitro dissolution should be provided in the documentation for marketing authorization. In vitro dissolution tests and specifications for quality control should be based either on suitable compendial specifications or on the in vitro performance of the test batches used to generate material for the equivalence study. Where sufficient full-scale process validation batches are not prepared in the immediate post-approval period, several batches (two or three are recommended) of the test product should be manufactured in the pre-approval period according to standard, consistent, well-documented procedures. Two of these batches should contain at least 100,000 units or 10% of the intended production batch, whichever is larger. The third, if prepared, may be smaller (e.g., 25,000 units). Justification should be provided if smaller batches are used. Material from these test batches is used both to provide material for dissolution studies and also for equivalence testing. Dissolution tests on these batches should be based on physiologically relevant media and test conditions. When deciding upon the test methods to be used, it is recommended to start experiments with widely-used compendial methods “paddle” and “basket”, and try other methods (“flow through cell” etc.) when these fail to demonstrate sufficient discriminatory power. Dissolution profiles are recommended, even when a single point compendial dissolution test is available. In case of immediate release pharmaceutical products a single point dissolution may be used for quality control purposes. Specifications of the dissolution performance of subsequently manufactured batches will be based on the results of the dissolution tests performed on the test batches. Whereas it is undisputed that the value of dissolution testing will be enhanced if the dissolution results can be shown to reflect important changes in formulation and/or the manufacturing process by in vivo studies the practicalities are still under discussion. It is not recommended to broaden the dissolution specification based on the performance of the test batches beyond the point where equivalence between the test material used in the equivalence study and subsequently manufactured production batches can no longer be assumed.
The following data should be recorded and included in the documentation for marketing authorization:
(a) Comparative dissolution results for test and reference pharmaceutical products after intervals appropriate for products and conditions under investigation (normally a minimum three sampling times).
(b) For each sampling time, the observed data, individual values, the range and the coefficient of variation (relative standard deviation) should be reported.