A 25-year-old woman, presents to the emergency department co…

A 25-year-old woman, presents to the emergency department complaining of severe flu-like symptoms and intense cravings. She reports a history of substance abuse. Over the last week, she describes experiencing severe muscle aches, nausea, vomiting, diarrhea, sweating, and chills. On physical exam, you note mydriasis, restlessness, and yawning. Based of this information, which substance is the patient withdrawing from?