Final answer:
Morphine is the correct answer because it is an opioid agonist; discontinuing its use and replacing it with a non-opioid can lead to withdrawal symptoms.
Step-by-step explanation:
When discussing a drug that could cause withdrawal symptoms if used to replace a long-term opioid agonist, the key is to identify the substance among the options given (acetaminophen, ibuprofen, morphine, aspirin) that has opioid properties.
Morphine is an opioid agonist and has analgesic properties, meaning that it decreases pain by binding to opioid receptors in the brain. If morphine were to be discontinued suddenly and replaced with a non-opioid pain reliever like acetaminophen, ibuprofen, or aspirin, the patient would likely experience opioid withdrawal symptoms due to the lack of opioid effect. These withdrawal symptoms can include severe pain, flu-like symptoms, and psychological effects such as anxiety and depression.