News

The following article has been authored by John Heaney. Does the presence of a resident sampling probe affect the hydrodynamics of a dissolution vessel?  Yes, yes it does.  The more important questions are how strong is the change in the hydrodynamics and is it strong enough to affect testing? USP <1092>, an advisory chapter addresses this directly with:  Sampling probes may or may not remain in the vessel throughout the entire run. Sampling probes or fiber-optic probes can disturb the hydrodynamics of the vessel; therefore, adequate validation should be performed to ensure that the probes are not causing a significant...

The following article has been authored by John Heaney.  Coning of disintegrating dosage forms is fairly common when using Apparatus 2 (Paddles) to perform dissolution testing.  The reason for this is the spinning of the paddle causes a cone shaped zone to form directly beneath it where there is low hydrodynamic activity.  In other words, it’s a bit of a dead zone where the stirring has little effect, and the particles are allowed to settle. Depending on the formulation this coning can be problematic.  It can prevent drug from dissolving in the media due to a reduction in the effective...

The following article has been authored by John Heaney. Compared to the rest of dissolution testing, small volume dissolution is in a bit of a strange position within the industry.  The bulk of dissolution testing is set around well-defined apparatus with specific dimensional tolerances and a 1 L glass vessel with a hemispherical bottom.   Small volume dissolution can vary widely, the main commonality being that the maximum capacity of the vessels is significantly smaller than 1 L. The first question one may ask is why do small volume dissolution at all?  As pharmaceutical technology improves, with better chemistry and things...

The following article has been authored by John Heaney.   The debate about the prednisone performance verification test (PVT) versus the ASTM enhanced mechanical calibration has gone on since the inception of ASTM chapter 2503.  Both are different means of providing an answer to the same question,” Is my dissolution tester suitable for use and can I trust the data from it?” The prednisone PVT is typically performed after a mechanical qualification of the dissolution tester which, if one follows USP 711, has wider tolerances for passing than ASTM 2503.  However, if one follows the suggestions in USP Guideline on...

The following article has been authored by John Heaney.   The USP chapter <711> says that dissolution testers should be free of any noticeable vibration.  While the chapter technically addresses the issue, it’s a far cry from the detail of the standards laid out for vessels, paddles, and baskets.  The reason for this likely lies with vibration itself. Vibration has both frequency and amplitude and those can be varied over a near limitless range. Sound is one of the most common forms of vibration that most people deal with on a day-to-day basis and is a good example of how...