What does break through pain mean?

what does break through pain mean?

Break through pain means;

Imagine a patient had cancer… and we started some analgesic (iv/ epidural… anything) it is going on continuously…

Due to some trival reasons which can be obvious ( some movement of limb/strain)/ some times not obvious reasons like coughing/sneezing… suddenly patient will complain of pain… Which is more acute& intense…

This is called break through

We need to use…some other drug/ some other modality to reduce this…

Thank you very much for the elaborated explanation sir ! And also thanks a lot for helping me understand this with ease