man, I'm really happy when someone actually asks questions about drugs that doctors prescribe them. I know SOOO many people who just pop whatever pills their doc prescribes.
Vyvanse is d-amphetamine (dextroamphetamine) that is linked or bound to a naturally occurring amino acid, l-lysine. This compound is inactive (is inert) until this bond is broken by enzymes (metabolized) in the GI tract (stomach and intestine), releasing the active drug, d-amphetamine.
Since there are no enzymes in the nasal passages that can break this bond, blood levels would be 96% lower if Vyvanse were snorted than if d-amphetamine were snorted, and 75% lower if it were injected. When given intravenously to adults with histories of stimulant abuse, Vyvanse produced less euphoric effects than d-amphetamine, and the effects were not significantly different than intravenous placebo.
Absorption of Vyvanse is delayed, compared to d-amphetamine, and without a quick onset, the intensity and "likability" (drug-seeking behavior) drops. When Vyvanse is taken orally, increasing doses produce increasing blood levels, but only up to a certain point (130 - 150 mg), beyond which higher doses will not produce higher blood levels, which might reduce abuse potential and toxicity from overdose.
I take 20mg Adderal IR and 30mg Adderal XR daily and have been on this for almost a year. Suddenly, the effects aren't the same. I'm sloppy again, speaking way too much, unorganized...I'm back to where I was before I started taking meds. My doc won't up the dose or try different meds so I don't know what to do.