Breakthrough pain is severe pain that comes on suddenly in people who are taking medicines that usually keep their pain under control. It "breaks through" the pain relief that a person has been getting from taking medicines for persistent or chronic pain.

Breakthrough pain usually lasts for a short time, but it is very intense pain. It can happen right after a specific physical activity or just before it's time to take another dose of pain medicine. Sometimes breakthrough pain happens for no known reason. If it happens often, this may mean that the dose of regular pain medicine may need to be changed.

Breakthrough pain is treated with fast-acting opiate pain relievers, such as morphine, oxycodone, or fentanyl. These medicines last just a short time in the body.

Breakthrough pain is most common in people who have cancer. But it can happen in anyone who is taking pain medicine on a regular schedule for persistent or chronic pain.