True about naltrexone is all except

Ans. d (Is a opioid agonist). (Ref. Pharmacology by KD Tripathi - 6th pg. 467)Agonist-antagonists (K analgesics)Nalorphine, Pentazocine, ButorphanolPartial/weak m-agonist + k antagonistBuprenorphinePure antagonistsNaloxone, Naltrexone, NalmefeneNALTREXONE# Pure opioid antagonist, chemically related to naloxone.# Orally active and long duration of action (1-2 days) makes it suitable for 'opioid blockade' Rx in post-addicts.# It is more potent than naloxone.# Alcohol craving is also reduced by naltrexone; it is being used to prevent relapse of heavy drinking# HepatotoxicNewly developed opioid antagonist Nalmefene:# Hepatotoxic# Has higher oral bioavailability &# Is long acting.