Opioids group is the strongest analgesic group available up to date . It works through binding to endogenous opioid receptors. Which leads to closure of presynaptic calcium Ca channels and halt the release of excitatory neurotransmitters. Additionally opioid receptors enhance the efflux of positive K ions from postsynaptic neurons which results in more suppression of the pain action potential that boosts the opioid analgesic effects