Rheo-dissolution: A new platform for the simultaneous measurement of rheology and drug release.

There is great potential to improve drug delivery through the use of in-situ gelling delivery systems. Here we demonstrate a technique capable of measuring changes in rheology (gelation and/or dissolution) of in-situ gelling delivery systems on contact with physiological fluid, while simultaneously analysing drug release. An ocular in-situ gelling formulation (gellan and timolol maleate) and an in-situ gelling oral liquid (alginate and metronidazole) were used as exemplar formulations. The method allowed profiling of increasing gellan concentration resulting in a reduction of timolol maleate released into simulated lacrimal fluid. When alginate was used as an in-situ gelling oral formulation there was a rapid increase in G' on contact with simulated gastric fluid. When this was changed to simulated intestinal fluid, drug release rate increased rapidly, coinciding with alginate gel dissolution. This work highlights the potential of this technology as a tool in development and optimisation of these increasingly popular delivery systems.