Please explain reasons why this hydrocodone is giving me energy?

Endorphin activity: When we need energy, our body produces endorphins. Hydrocodone, or any opioid, does the exact same thing to receptors as endorphins/enkephalins. Over time, if you keep taking it, your body will stop making endorphin, and when you don't have the hydrocodone, you will feel lethargic, and potentially depressed/listless as well. This is part of the road to addiction. Please talk to your physician.