Can prolonged use of Adderall (dextroamphetamine and racemic amphetamine) XR cause or contribute to adrenal failure?

No Adrenal Failure. Adderall (dextroamphetamine and racemic amphetamine) or other stimulant medications do not cause adrenal failure (a serious life threatening disorder). In the popular magazines they talk about "adrenal fatigue" which ahas a variety of symptoms. There is little support in the science literature of this "syndrome". If you have symptoms that you have not had before, talk with your doctor and see if a workup is necessary.
Maybe. All medications have side effects, but to the best of my knowledge, long term use does not lead to adrenal insufficiency.