What are opioid antagonists?

Naloxone (reverses coma and resp depression of opioids, effects of heroin overdose. IV injection after 30 s reverse the effects half life 1-3 hours, competitive antagonist at mew (10 times higher affinity), k and lambda) Naltrexone (longer duration of action than naloxone, hepatotoxic) These have high affinity for opioid Rs but don't activate response, normal individuals no effect, if pt takes opioids reverses effect rapidly w/ sx of opiate withdrawal