Measurement of the Surface Area Changes During the Dissolution of Poorly Soluble Drugs using a Wide Angle Photosedimentometer

Using a Wide Angle Photosedimentometer, surface area changes during the dissolution of suspended particles of frusemide, glibenclamide and bendrofluazide have been measured. The method consisted of recording the change in optical density that occurs whilst the drugs are agitated in water in a 4cm square photosedimentometer cell. It was found that initially a high surface area was recorded which diminished exponentially with time and obeyed first order kinetics. From the surface area measurements, graphs of percentage drug dissolved against time were calculated and plotted and these profiles were found to correlate with similar plots of dissolution rate produced by analysing the amount dissolved spectrophotometrically. It was concluded that the surface area method offers an alternative technique for the measurement of the dissolution rate of poorly water soluble drugs, particularly when no adequate method exists for analysing the dissolved fraction.