You mean Vyvanse? (L-lysine-d-amphetamine) I'm assuming you're trying to get more of the upper effect that both these drugs give you....yeah?
Btw it's illegal to give medical advice like this so anything I say is not to be considered legit at all....so first of all ask your doctor.
But
The idea behind it (vyvanse) is that it doesn't work till an enzyme in your liver cleaves off the amino acid (L-lysine) which allows the amphetamine part of the drug to become active. Essentially, this makes it so that railing (snorting) it doesn't do anything to you. A lot of kids crushed up Adderal XR and ate/snorted the powder which was a much stronger upper than the extended release version so this drug was created to stop the street use of ADD medication. A ton of doctors are switching to it.
The new drug, vyvanse is called a "prodrug" because it's supposed to be very difficult to abuse since it's effectiveness depends on your body breaking the drug down into a useable form. Before the amino acid is broken off the amphetamine it does nothing to you, so it has to go through your liver/intestines first. Got it?
Ok, so if you took both.... from what I understand, both are dopamine/norepinephrine reuptake inhibitors, meaning that those neurotransmitters remain in your synatic cleft for longer, and hence their effects are increased. Both of these NT's are "uppers" and cause increased heart rate, focus, blood pressure, learning, mood, motivation, blah blah blah..... both drugs have the same (well ok similar) mechanisms in your brain so there is really no need to take both, and doing so could be dangerous.
Don't take both. Just take one or the other, if you take both, they shouldn't have adverse effects directly to one another (DO NOT QUOTE ME ON THIS, THEY ARE MERELY IN THE SAME FAMILY OF DRUGS I HAVE NO IDEA WHAT I'M TALKING ABOUT LOL) but they may increase your bloodpressure/heart rate to dangerous levels. You've heard of the kids dying from having too many energy drinks and playing sports? Their hearts failed. Not a fun way to go.
Just ask your doctor for a stronger ADD drug if you want more effects. I take adderal and it works perfectly. I strongly recommend it.
Good luck!