The brain responds to an opioid by releasing a powerful chemical called dopamine. This rewards the brain with “pleasure” and may encourage repeated use of the drug.
If more opioids are taken than were prescribed or for longer than what was recommended, the body’s natural tendency to produce dopamine (and feel pleasure) will eventually slow down.
What doesn’t slow down is feeling the need for the drug. This can lead to taking higher and higher doses to try to find the satisfaction the drug once provided.
Even though the doses get higher and higher, the pain gets worse. This results in a vicious cycle of increasing doses but poorer pain control.