Excipient (pharmacologically inactive substance)
What is it?
Starch glycolates are of rice, potato, wheat or corn origin. Sodium starch glycoate is a white to off-white, tasteless, odorless, relatively free flowing powder.
Sodium starch glycolate is used as a pharmaceutical grade dissolution excipient for tablets and capsules. Sodium starch glycolate absorbs water rapidly, resulting in swelling which leads to rapid disintegration of tablets and granules. It is used as a disintegrant, a suspending agent and as a gelling agent. Without a disintegrant, tablets may not dissolve appropriately and may effect the amount of active ingredient absorbed, thereby decreasing effectiveness. 
 Dave RH. Overview of pharmaceutical excipients used in tablets and capsules. Drug Topics (online). Advanstar. 10/24/2008 http://drugtopics.modernmedicine.com/drugtopics/Top+News/Overview-of-pharmaceutical-excipients-used-in-tabl/ArticleStandard/Article/detail/561047. Accessed 08/19/2011