Journal
JOURNAL OF CONTROLLED RELEASE
Volume 70, Issue 3, Pages 383-391Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/S0168-3659(00)00366-7
Keywords
swelling; translocation; release mechanism; drug solubility; hydroxypropyl methylcellulose; hydrophilic matrix
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The aim of this wort; was to study the release mechanisms of drugs having different solubility (buflomedil pyridoxalphosphate 65%, sodium didofenac 3.1%, nitrofutantoin 0.02% w/v,) from hydroxypropyl methylcellulose (HPMC) matrices by concomitantly studying swelling, diffusion and erosion fronts movement and drug delivery. The main goal was to clarify the role played by polymer swelling in drug transport. The results showed that the rate and amount of drug released from swellable matrices was dependent not only from drugs dissolution and diffusion but also from solid drug translocation in the gel due to polymer swelling. In fact, as drug solubility decreased, the slower drug dissolution rate in the gel layer allowed drug particles to be transported close to the matrix erosion front. The presence of solid particles in the gel reduced the swelling and the entanglement of polymer chains and affected the resistance of gel towards erosion. As a consequence, the matrix became more erodible. The erosive delivery accelerated after the matrix had been completely transformed into the rubbery state, particularly when a considerable amount of solid drug particles remained in the gel phase. (C) 2001 Elsevier Science B.V, All rights reserved.
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