Taking 40 mg vyvanse (lisdexamfetamine). i can tell the meds wear off late afternoon but at night i can't fall asleep? is the medicine not completely out of my system?

Talk to doctor: While most of Vyvanse (lisdexamfetamine) is eliminated from the body in about 8 hours (varies with the individual), a small amount takes longer to be metabolized and may cause difficulty falling asleep. Compare your sleep on a day you don't take Vyvanse (lisdexamfetamine) to be sure. Discuss what to do with prescribing doctor. Options may be to lower the dose, take earlier in the morning or try a shorter-acting stimulant. Good luck.