An irreversible agonist is a type of agonist that binds permanently to a receptor through the formation of covalent bonds. A few of these have been described, including Paracetamol.[2][3] A biased agonist is an agent that binds to a receptor without affecting the same signal transduction pathway. Oliceridine is a µ-opioid receptor agonist that has been described to be functionally selective towards G protein and away from β-arrestin2 pathways.[4]