How do opiates work in the body?

Opioid receptors: We make our OWN opioids - endorphins/enkephalins and others - and they act on receptors that cause the release of neurotransmitters in certain brain areas responsible for energy, euphoria, pain relief and other actions. Natural opioids (morphine, codeine), semisynthetics (oxycodone, hydrocodone etc) and synthetics (methadone, fentanyl etc.) act on the same receptors, of which there are 5 subtypes