Estimation of the percolation thresholds in dextromethorphan hydrobromide matrices.
Percolation theory is a multidisciplinary theory that studies chaotic systems. It has been applied in the pharmaceutical field since 1987. Knowledge of the percolation threshold -- one of the most important concepts in percolation theory -- results in a clear improvement of the solid dosage form design. The percolation threshold is the concentration showing the maximum probability to obtain, for the first time, a percolating cluster of a substance. In this work, the percolation thresholds of dextromethorphan.HBr/Eudragit RS-PM inert matrices were estimated. The drug percolation threshold was estimated as 0.3691+/-0.0541 (P=0.05) of the total porosity (ranging between 23 and 36% w/w of drug). The SEM micrographs of the matrices are consistent with the estimated percolation range. In agreement with previous reports, different percolation thresholds were found for the matrix forming excipient Eudragit RS-PM. The site percolation threshold (based on the release properties) ranged between 10 and 20% v/v of the excipient, the site-bond percolation threshold (estimated from the mechanical properties) between 29.5 and 34% v/v of the excipient and the swelling percolation threshold between 34.3 and 46.9% v/v of the excipient. These percolation ranges are in agreement with those found previously for Eudragit RS-PM matrices containing naltrexone.HCl and morphine.HCl.
Universidad Autónoma Metropolitana-Xochimilco, Departamento de Sistemas Biológicos, Calzada del Hueso 1100, Colonia Villa Quietud, C.P. 04960, Mexico D.F.
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Melgoza
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Rabasco
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Caraballo
D000180:Acrylic Resins / Q000737:chemistry*; D000996:Antitussive Agents / Q000737:chemistry*; D002626:Chemistry, Pharmaceutical; D003915:Dextromethorphan / Q000737:chemistry*; D017711:Nonlinear Dynamics; D011109:Polymethacrylic Acids; D016062:Porosity
D000180:Acrylic Resins; D000996:Antitussive Agents; D011109:Polymethacrylic Acids; C038300:methylmethacrylate-methacrylic acid copolymer; D003915:Dextromethorphan