Opioid antagonist that can be given orally?
Correct Answer: Naltrexone
Description: Ans. a (Naltrexone) (Ref KDT 6th/464, 467)Naltrexone differs from naloxone in being orally active and having a long duration of action (1-2 days) which makes it suitable for 'opioid blockade' therapy of postaddicts.Opioids & Opioid AntagonistsAgonist-antagonists (k-analgesics)Partial/weak m agonist + K antagonistPure antagonistNalorphineBuprenorphineNaloxonePentazocine NaltrexoneButorphanol NalmefeneNALTREXONE# Pure Opioid Antagonist like naloxone# Chemically related to naloaxone# More potent than naloxone.# Differs from naloxone in that it is orally active and has longer duration of action (1-2 days).# USES:- Hence suitable for "opioid blockade therapy" of postaddicts: 50 mg/day orally.- Also useful to reduce alcohol craving- Used to prevent relapse of habit drinking.# S/E:- Nausea- Headache- Heptotoxicity (at high doses).THE OPIOID ANTAGONISTSIntroduction# The pure opioid antagonist drugs naloxone, naltrexone, and nalmefene.# These agents have a relatively high affinity for m opioid binding sites.# They have lower affinity for the other receptors but can also reverse agonists at d and k sites.Pharmacokinetics# Naloxone is usually given by injection and has short duration of action (1-2 hours) when given by this route.# Nalmefene, the newest of these agents, is a derivative of naltrexone but is available only for intravenous administration.# Like naloxone, nalmefene is used for opioid overdose but has a longer half-life (8-10 hours).# When given intravenously to a morphine-treated subject, the antagonist completely and dramatically reverses the opioid effects within 1-3 minutes.Clinical Use# Naloxone is a pure antagonist and is preferred over older weak agonist-antagonist agents that had been used primarily as antagonists, e.g., nalorphine and levallorphan.# NALOXONE in the treatment of acute opioid overdose.# Because of its long duration of action, NALTREXONE has been proposed as a maintenance drug for addicts in treatment programs. A single dose given on alternate days blocks virtually all of the effects of a dose of heroin.# NALTREXONE decreases the craving for alcohol in chronic alcoholics, and it is FDA approved for this purpose.
Category:
Anaesthesia
Get More
Subject Mock Tests
Practice with over 200,000 questions from various medical subjects and improve your knowledge.
Attempt a mock test nowMock Exam
Take an exam with 100 random questions selected from all subjects to test your knowledge.
Coming SoonGet More
Subject Mock Tests
Try practicing mock tests with over 200,000 questions from various medical subjects.
Attempt a mock test now