Often it is suggested that one should use a de-gassed or de-aerated dissolution medium. Unfortunately, conducting a dissolution test using such a condition makes the test and results obtained invalid, why?:
- Dissolution tests are conducted to evaluate drug dissolution characteristics in vivo, i.e., in the human GI tract. The GI tract contents are not de-aerated or de-gassed, therefore, in vitro tests conducted in a de-gassed medium will not be reflective of the in vivo environment and thus the results will be invalid.
- Commonly suggested procedure for preparing a de-aerated medium is by vacuum filtering of heated (41-45 ºC) dissolution medium. Dissolution tests are conducted at 37 ºC, thus dissolution medium temperature will change from ~45 to 37 ºC during testing. Therefore, not only does de-aeration create a non-physiological condition, but also introduces instability in the medium characteristics during testing.
For more appropriate drug dissolution testing, the medium should be equilibrated at 37 ºC, which would provide a more appropriate physiological condition and stability in the testing environment.
