<prompt> True about naltrexone is all exceptActs on opioid receptorsIs used in treatment of alcohol dependenceIs used to reduce craving in dependenceIs a opioid agonist  <response>: Ans. d Is a opioid agonist. Ref. Pharmacology by KD Tripathi - 6th pg. 467Agonist-antagonists K analgesicsNalorphine, Pentazocine, ButorphanolPartialweak 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. 