Simultaneous probing of swelling, erosion and dissolution by NMR-microimaging – Effect of solubility of additives on HPMC matrix tablets

• Extensive studies of extended release tablets based on hydrophilic polymers have illuminated severalaspects linked to their functionality. However, in some respects key factors affecting the mechanismsof release are yet unexplored. In the present study, a novel NMR-microimaging method has been usedto study the influence of the solubility of additives in extended release hydroxypropyl methylcellulose(HPMC) matrix tablets. During the course of the tablet dissolution the movement of the swelling anderosion fronts were studied simultaneously to the release of both polymer and additives. Moreover,the focused beam reflectance measurement (FBRM) technology was for the first time assessed for bothrelease and dissolution rate studies of poorly soluble particles. The studied formulations comprised solelyHPMC, 40% HPMC and 60% mannitol (Cs = 240 mg/ml) and 40% HPMC and 60% dicalcium phosphate (DCP)(Cs = 0.05 mg/ml). The dissolution rate of the tablets was highest for the HPMC/mannitol formulation,followed by HPMC/DCP and plain HPMC tablet. A contrasting order was found regarding the degree andkinetics of swelling. The results were interpreted in light of how the mass transport in the gel layer isinfluenced by the solubility of additives. A mechanistic model, considering osmotic pressure gradient andthe effective diffusion of the dissolution medium in the gel is proposed.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Farmaceutiska vetenskaper (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Pharmaceutical Sciences (hsv//eng)

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