Quote from: NewStem on May 13, 2013, 02:49 amQuote from: SelfSovereignty on May 11, 2013, 01:17 amIt's a little less straight forward than that. Adderall XR is an extended release formulation -- basically that means that it dissolves more slowly in your intestines than the instant release tablets.So 20mg of instant release is instantly released and pretty much totally absorbed within an hour of ingestion. Give or take -- I always seemed to reach peak levels almost exactly 43 minutes after taking it, but your mileage may vary and I'm no biologist and all that disclaimer stuff :)20mg of XR though, would be released slowly over a period of about 2 hours maybe (give or take). I've never paid attention the extended release ones though, so I can't compare my own experience with them. In the end though, it's basically like taking a quarter of an instant release every 20-30 minutes. That's the difference. Which is better is up to you and the situation you're in :)I just want to step in and correct your description of the mechanism of Adderall XR: Half the contents in an Adderall XR cap are the same form of amphetamine present in the IR version. The other half is a form of amphetamine metabolized lower in the digestive system, its effects beginning maybe 4 or 5 hours after the initial release. The drug does NOT release slowly over time, but rather releases in 2 waves many hours apart.Indeed, you're right. Half of the medication is contained in beads that dissolve and release the four amphetamine salts 4 hours after initial ingestion (give or take). Since the four salts in adderall all have slightly different digestive profiles anyway, it's a little less straight forward than two waves, but again: you're absolutely right about the XR mechanism releasing the four salts in two waves. Thank you for the correction :)