Dome Matrix® technology: effect of drug solubility on release kinetics of swellable delivery modules.

ALVARO F JIMENEZ-KAIRUZ; ELENA LOSI,; ORAZIO LUCA, STRUSI; FABIO SONVICO,; RUGGERO BETTINI,; PAOLO COLOMBO,

San Antonio, TX.

Congreso; American Association of Pharmaceutical Scientists: Annual Meeting and Exposition; 2006

Purpose.To study the swelling and the release kinetics of drugs having different solubility from curved shaped hydrophilic matrices, used as modules to prepare assembled system.Methods.The studied modules are disc hydrophilic matrices with one base convex and the other concave, named Dome Matrix. Matrices (125 mg weight) were formulated with Methocel K100 and a very soluble drug, buflomedil piridoxal phosphate (BPP) or a poorly soluble drug, riboflavin. The swelling and drug release were studied in water for BPP and in simulated gastric fluid for riboflavin at 37°C. In addition, drug release kinetics were studied also on two unit matrices assembled in differently configuration, i.e. in staked configuration, with the convex base inserted in the concave, and in void configuration, obtained soldering the two matrices with the concave bases facing each other.Results.The drug solubility and the type of assemblage influence the release kinetics from swellable matrix modules. For BPP, the analysis of the release kinetics with an exponential equation led to anomalous Fickian kinetics (diffusion exponent n=0.6).This release behaviour was measured also for the assembled modules, but slower release rate of the drug was determined.On the contrary, the release of riboflavin from the individual modules and from the assembled systems showed significant different kinetics. In fact, the exponent n values were close to 1, thus indicating a linear release. The observation of the swelling of matrices loaded with the two drugs shows different behaviours: in the case of the soluble drug an important gel layer thickness developed on the glassy core controlling by the diffusion the drug release, whereas for the poorly soluble drug the release was controlled mainly by the erosion of the thin gel layer, in which large amount of un-dissolved drug is present.Conclusion.The Dome Matrix module assembling shows release kinetics determined by the geometry of the assembled system and by the drug solubility. Different drug release kinetics from systems assembled with the same individual matrix modules could be obtained.