Beta-endorphin
β-END
What it isEndogenous opioid peptide acting at mu and delta receptors.
Why this oneIt is the endogenous ligand whose system every opioid drug engages.
What limits itIts release during stress and exercise is why opioid antagonists blunt exercise-induced analgesia.
NO BOXED WARNINGS
Principal riskEndogenous or dietary; no boxed warning applies