MEDICAL PHYSIOLOGY

Detailed explanation-1: -An antagonist is a drug that blocks opioids by attaching to the opioid receptors without activating them. Antagonists cause no opioid effect and block full agonist opioids. Examples are naltrexone and naloxone.

Detailed explanation-2: -When binding to the pain pathway opioids provide pain relief, however, when binding to the reward pathway, opioids cause euphoria and release a key neurotransmitter known as dopamine. Dopamine signals the neurons (brain or nerve cells) of the body to create a pleasurable feeling or “high”.

Detailed explanation-3: -The two most commonly used centrally acting opioid receptor antagonists are naloxone and naltrexone. Naloxone comes in intravenous, intramuscular, and intranasal formulations and is FDA-approved for the use in an opioid overdose and the reversal of respiratory depression associated with opioid use.

Detailed explanation-4: -When a drug binds to an opioid receptor site as an agonist, it produces a number of effects, such as analgesia, pruritus, nausea, and respiratory depression. Opioid antagonists are drugs that also bind to opioids for receptors, competing with agonists for receptors sites, but producing no analgesia.