It is possible to become addicted to prescription opioids accidentally, and many people do. This is often seen in elderly people, but it can actually happen to anyone who uses them.
Accidental abuse occurs because people don't understand the addictive nature of their medications. They may not be getting the pain relief they're looking for, so they increase their dosage. Their intentions are not to get high or experience euphoria. They're just looking to decrease their pain.
It's also possible to accidentally abuse these drugs when you take them for too long. This happens far too often, and doctors will prescribe them long-term for some patients.
Purposeful or intentional abuse of opioid drugs is very common. People know that they will get high or experience a euphoric effect when they take them. They'll abuse them on their own, or in combination with other drugs and alcohol.
An addiction can take place in both places. It's important to know how dangerous these drugs can be. Abusing them for too long will eventually lead to addiction.