A nurse is providing teaching to a client with opioid use disorder who is prescribed naltrexone. Which client statement demonstrates an accurate understanding of how naltrexone works?

A. "This medication blocks opioid receptors so opioids cannot produce a euphoric effect.": Naltrexone is a competitive opioid antagonist that binds to mu-opioid receptors without activating them. By occupying these receptors, it prevents exogenous opioids from producing euphoric or reinforcing effects, helping to reduce the risk of relapse in individuals with opioid use disorder. B. "This medication increases serotonin levels to improve mood and decrease drug use.": Medications that increase serotonin, such as selective serotonin reuptake inhibitors (SSRIs), target depression and anxiety, not opioid receptor activity. Naltrexone’s mechanism does not involve modulation of serotonin or other monoamine neurotransmitters. C. "This medication replaces opioids in my body to prevent cravings.": Medications like methadone or buprenorphine act as opioid agonists or partial agonists to prevent withdrawal and cravings. Naltrexone does not replace opioids or provide agonist activity; it strictly blocks receptor activation. D. "This medication reduces withdrawal symptoms by partially activating opioid receptors.": Partial agonists such as buprenorphine can reduce withdrawal symptoms by providing low-level receptor stimulation. Naltrexone, however, is a pure antagonist and does not activate receptors, so it does not alleviate withdrawal symptoms and should only be started after detoxification.