Could someone explain hypromellose matrices to me?

[>Marquis<]

Okay, they're used for controlled release tablets, right? But how do they function? I couldn't make any sense of what I found on google, I'm a layman and don't know anything about oral drug delivery systems but would like to. Chas!

 

[redeemer]

I've got this lying around on my computer if you're interested:

Li, Chi L.1; Martini, Luigi G.; Ford, James L.; Roberts, Matthew
The use of hypromellose in oral drug delivery
Journal of Pharmacy and Pharmacology, Volume 57, Number 5, May 2005, pp. 533-546(14)