Systematic classification of tablet disintegrants by water uptake and force development kinetics.

OBJECTIVE: Water uptake and force development of disintegrating tablets provide a high degree of information about the disintegration mechanisms and process itself. An apparatus for the simultaneous measurement of water uptake and force development of tablets is presented, and the gathered data are analysed.

METHODS: Flat faced, 10 mm, dibasic calcium phosphate tablets containing 2% disintegrant are investigated with the newly constructed apparatus. The force is determined with a texture analyser, whereas the water uptake is recorded by a balance. Different measurement regimes are compared with each other. Measured curves are analysed according to their shape and fitted with a modified Hill equation.

KEY FINDINGS: Known disintegration mechanisms can be confirmed with the newly constructed apparatus - swelling for sodium starch glycolate and croscarmellose sodium, and shape recovery for crospovidone disintegrants. Different brands of polacrilin potassium act by different mechanisms. All curves could be fitted successfully with a modified Hill equation. A novel classification to facilitate the appropriate disintegrant selection is presented on basis of the fit parameters.

CONCLUSION: The new apparatus allows the acquisition of water uptake and force data simultaneously. Parameters calculated with the modified Hill equation provide a simple way to classify disintegrants according to their behaviour.