Naltrexone is:-: (A) Mu receptor agonist, (B) Delta receptor agonist, (C) Kappa receptor agonist, (D) Mu receptor antagonist
Answer is D. Naloxone, naltrexone and nalmefene are potent mu receptor antagonists with significant blocking action at kappa and delta receptors also. Naloxone is given parenterally (ineffective orally) and is a very sho acting drug. Nalmefene is also given parenterally but has a longer half life. Naltrexone is long acting orally effective opioid antagonist. Naloxegol-Naloxone conjugated to PEG polymer