How does the concept of 'intrinsic activity' relate to the difference between a full opioid agonist and a partial opioid agonist?

Intrinsic activity, also known as efficacy, is a measure of the ability of a drug to activate a receptor and produce a maximal biological response once bound. It explains the difference between full opioid agonists and partial opioid agonists. A full opioid agonist, such as morphine or fentanyl, has high intrinsic activity at the mu (μ) opioid receptor. This means that when a full agonist binds to the mu receptor, it can elicit a maximal response....