1 <h5>Introduction</h5> Hydroxypropylmethylcellulose (HPMC) is widely employed for controlled delivery due to its low toxicity and compatibility with many drugs. The influence of a number of physicochemical and technological factors on drug release from HPMC matrix tablets has been studied ( Roberts et al., 2007 ). The release is faster as the HPMC molecular weight decreases for the lower viscosity grades ( Kim and Fassihi, 1997a,b ) whereas little differences are observed among the largest viscosity grades ( Kurahashi et al., 1996 ). Drug delivery also depends on the loading dose and drug solubility ( Kurahashi et al., 1996; Xu and Sunada, 1995 ). Large concentrations of highly soluble drugs show increased release rates from HPMC matrices ( Kim and Fassihi, 1997a ). However, the diffusion coefficient of oxprenolol hydrochloride (water soluble) is lower than that of theophylline (less water-soluble), a fact that was attributed to drug–polymer interactions ( Bettini et al., 1995 ). Drug delivery from hydrophilic matrices is accomplished via swelling, dissolution and/or erosion and the release kinetics may be Fickian or non-Fickian ( Kim and Fassihi, 1997a ). Swelling of HPMC is not influenced by variations of ionic strength and pH, due to the non-ionic
International Journal of Pharmaceutics – Elsevier
Published: Jul 29, 2011
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