(W0930-08-47) Impact of Change in Test Conditions on Alginate Raft Strength

Purpose: Alginate-based raft formulations have been used for the symptomatic treatment of heartburn and esophagitis. Various alginate-based raft formulations are available commercially. Alginate gel provides a floating physical barrier against acid reflux from the stomach. The barrier floats on top of stomach content as a raft. The desired formation of the raft and its strength play a key role in therapy. Better raft strength is one of the key indicators of the performance of the dosage form inside the gut. The objective of the study was to understand the impact of raft testing conditions on alginate raft strength.

Methods: Rafts were formed by adding a maximum dose of liquid product to 150 mL of 0.1M HCl, maintained at 37 °C in a 250 mL low-form glass beaker. Each raft was formed around an L-shaped stainless steel wire probe held upright in the beaker throughout the whole period (30 min) of raft development. After 30 min of raft development, the beaker was placed on the platform of Texture Analyzer (Model-TX Plus, make-Stable Microsystems, UK), and the wire probe was hooked onto the Texture Analyzer arm and pulled vertically up through the raft at a rate of 5 mm/s. The force (g) required to pull the wire probe up through the raft, was recorded by the Texture Analyzer. The test method conditions such as a change in volume of media, and incubation time for raft formation, were carried out using the standard method (n= 3) as described above. In addition, the change in equipment condition such as a change in load cell was evaluated.

Results: The commercially available formulation was used for the evaluation. The raft strength was evaluated for each testing condition and was compared with the standard method of raft testing. The samples were evaluated for their physical appearance and coherence of the raft. The change in media volume (from 100 mL to 200 mL) impacts the raft strength. The optimum raft strength was observed at 150 mL. Change in incubation time (from 30 min to 2 hours) does not show a significant impact on the raft strength. An increase in load cell weight from 5.0 kg to 50 kg showed reduced raft strength. The load cell change study represents that the 5.0 kg load cell showed desired attribute for the raft strength testing method.

Conclusion: The incubation time of 30 min with 150 mL media volume showed optimum raft strength. In addition, the 5.0 kg load cell showed optimum raft strength. Overall, the study showed that the change in test conditions affects the raft strength.

References: [1] Alginate rafts and their characterization F.C. Hampson et al., International Journal of Pharmaceutics, 294 (2005), 137-147.


Figure 1: Effect of change in Media Volume


Figure 2: Effect of change in Incubation time


Figure 3: Impact of change in load cell on raft strength