Final answer:
Methadone has the longest elimination half-life among opioids.
Step-by-step explanation:
The opioid with the longest elimination half-life is methadone. Methadone is a synthetic opioid that is commonly used for the treatment of opioid dependence and chronic pain management. It has a half-life of around 15-60 hours, which means it takes a long time for the body to eliminate half of the drug.