News — dissolution testing

The following article has been authored by Chris Lewis. At times during dissolution testing, particularly with USP Apparatus 2 (paddle), a ‘cone’ can form in the bottom of a dissolution vessel.  This ‘cone’ is the result of the accumulation of undissolved material, such as excipients or drug particles, directly beneath the stirring paddle. This occurs because the center of the vessel's hemispherical bottom is a hydrodynamic "dead zone" where hydrodynamic shear forces are too low to lift the particles which allow gravity to settle them in a cone shape. Key Causes of Coning •                     Low Hydrodynamic Activity (Dead Zone): The...

Sample filtration is a critical part of dissolution testing, yet there is no universal solution that works for every application. The most effective filtration approach depends on the specific analytical method, sample properties, and filter characteristics involved. Each method should be evaluated individually to ensure optimal performance and reliable results. For established methods that already specify a particular filter type or micron rating, there may be little flexibility in filter selection. However, when developing new methods, a successful filtration strategy should be based on three key considerations: 1. Analytical Method Requirements The analytical technique being used—typically UV spectroscopy or HPLC—plays...

  The following article has been authored by John Heaney. Intrinsic dissolution is a specific niche of dissolution testing often reserved for early R&D.  The purpose is to provide scientists with an idea of the solubility of the API they’re studying.  This data can be invaluable as it will help determine the excipients required to develop an oral dosage form. There are 2 types of methods for this.  The first is a Rotating Disk (often called the Wood’s Apparatus) and the second is Stationary Disk.  In both cases a pellet of the pure drug is pressed into a drug compact...

The following article has been authored by John Heaney.   Compared to dissolution Apparatus 1 (Baskets) and Apparatus 2 (Paddles), Dissolution Apparatus 3: Biodissolution (the reciprocating cylinder) is quite rare.  However, it has some key advantages over the more common baskets and paddles which can make it very useful for key applications. Apparatus 3 consists of a glass cylinder with a mesh screen at the bottom moving up and down in a specified distance and rate within a glass dissolution vessel.  The dosage form is held within the glass cylinder.  Vessels are typically arranged in rows allowing the glass cylinder...

The following article has been authored by John Heaney.   Deaeration, or degassing, of dissolution media is not required for every dissolution method, but when it is required it is critically important.  The USP Prednisone PVT requires deaeration of the dissolution media and the tablet is formulated to show whether or not the deaeration method is adequate.  Deaeration tends to have a larger impact on dissolution results as compared to other factors regarding the dissolution test.  How this shows itself can change depending both on the apparatus, and the dosage being tested. How to deaerate is largely up to the...