SAG and Respiratory insufficiency due to muscle weakness: Thus far, opioids such as buprenorphine, PZM21, TRV-130, and SR17018 at the system level are antinociceptive and have lower respiratory depression in animal studies; at the molecular level, they also have in common miniscule loss of receptor from the cell surface, weak GRK recruitment, weak arrestin recruitment, weak receptor translocation to endosomes, and similar phosphorylation barcodes detected by western blotting.