Psyllium: a promising polymer for sustained release formulations in combination with HPMC polymers

Psyllium has a mucilaginous property that makes it a good candidate to be utilized as an
excipient in the preparation of controlled release systems. Various formulations were prepared
using theophylline as a model drug and investigated with a view to achieve an ideal slow drug
release profile. The addition of hydroxypropyl methylcellulose (HPMC) to psyllium significantly
reduced the burst release; however, the percentage of drug release within a 12 h period was
too slow and thereby inadequate. This was overcome by the addition of lactose as a hydrophilic
filler that enabled a slow release with roughly 80% drug release in 12 h. The inclusion of HPMC
within psyllium formulations changed the drug release kinetics from Fickian diffusion to
anomalous transport. Granulated formulations demonstrated slower drug release than
ungranulated or physical mixture and caused a change in the dissolution kinetics from
Fickian diffusion to anomalous transport. Milled granules showed more efficient controlled
drug release with no burst release. Milling of the granules also changed the drug release
kinetics to anomalous transport. Although psyllium was proved to be a promising polymer to
control the drug release, a combination of psyllium-HPMC and formulation processes should be
considered in an attempt to achieve a zero-order release.