Relationship between swelling, erosion and drug release in hydrophillic natural gum mini-matrix formulations

Compaction, compression and drug release properties of diclofenac sodium and ibuprofen pellets comprising xanthan gum as a sustained release agent

“…Xanthan gum, the control release agent included in the formulations, is known to have the ability to hydrate very rapidly in addition to exhibit a great swelling index compared to other gums (Sujja-areevath et al, 1998). It is speculated that drug release from tablets made of xanthan gum pellets was a result of hydration of the gum, which swelled extensively forming a barrier through which drug diffused.…”

“…Fickian diffusion was predominant but decreased after the first 3 h of dissolution while polymer erosion gradually increased and became the predominant mechanism for the rest of dissolution time. Such behaviour is well explained by the increase of thickness of the viscous gel layer around matrix that created a longer path length for diffusion which was followed by polymer chain relaxation, disentanglement and erosion (Sujja-areevath et al, 1996(Sujja-areevath et al, , 1998.…”

Incorporation of calcium salts into xanthan gum matrices: hydration, erosion and drug release characteristics

“…Xanthan gum is a high molecular weight anionic polysaccharide gum, produced by pureculture aerobic fermentation of a carbohydrate with the gram-negative bacterium, Drug release from xanthan gum matrix tablets is believed to be a complex interaction between; diffusion, swelling and erosion mechanisms [3][4][5] . When the hydrophilic polymer comes in contact with an aqueous medium the liquid penetrates and the matrix gradually hydrates and swells from the periphery to the centre of the tablet.…”

“…XG tablets consist of three regions: the highly swollen 3 outer gel layer, which acts as a diffusional barrier to retard drug release and further uptake of water; the moderately swollen, rubbery middle layer and the inner dry glassy core 4 . The thickness of the outer gel layer determines the diffusional path length of a water soluble drug and controls its release through Fickian diffusion during the initial phase 5 . However, as XG is hydrophilic in nature the polymer undergoes a relaxation process after hydration.…”

“…Furthermore, as swelling and erosion occur simultaneously, both mechanisms will control the overall drug release rate. Hence, a precise balance between the two factors is required to optimise drug release 5 . Sustained release XG matrix tablets have been investigated in numerous studies 4,[7][8][9] and provide evidences of XG's ability to prolong drug release.…”