A serious opioid crisis is affecting public health and economics, eroding people’s quality of life. 80% of patients who receive opioids suffer from adverse effects such as Opioid-induced constipation (OIC). However, there is no efficient medicine for these adverse effects. Notably, mainstream theory supports that analgesia effects are mainly controlled by CNS while OIC is predominately controlled by peripheral. In addition, the sites of action of opioid was based on the assumption that mu-opioid receptor antagonists (PAMORAs), did not cross the blood-brain barrier (BBB). Unfortunately, the BBB crossing of PAMORAs mislead the understanding of the role of the central nervous system (CNS) and gastrointestinal tract playing in the adverse effects such as opioid-induced constipation (OIC). Here, we developed a novel technology platform to prevent drugs from crossing the BBB. By applying this technology, naloxone- and oxycodone conjugates demonstrated superior potency, peripheral selectivity, pharmacokinetics, and effectiveness in rats compared to currently clinically used PAMORAs. By the help of these probes, it is revealed for the first time to that the mu-opioid receptors in the CNS played more important role in OIC than the peripheral receptors, which overturned the old theory. And the new theory points the way to better future PAMORAs drug design.