I take Adderall (dextroamphetamine and racemic amphetamine) for my ADD. I've been on it for over a yr and not had this problem before. But when the medication wears off, is constipation common?

Constipation. Yes constipation is one of the many side effects from taking adderall (dextroamphetamine and racemic amphetamine).
Constipation likely. Adderall and Vyvance are both Amphetamines, and can cause diarrhea. Once the medications have worn off, constipation is possible. Push fluids, take OTC Colace (docusate sodium) (stool softener) as needed. If symptoms persist, follow up with your PCM or a GI specialist. A varied diet high in fiber will help prevent symptoms of constipation as well.