<prompt> Partial agonist of opioid is -PethidineBuprenorphineMorphineButorphenol  <response>: Ans. is b d i.e., Buprenorphine Butorphenol o An opioid is a psychoactive chemical that works by binding to opioid receptors, which are found principally in the central and peripheral nervous system and GIT.o So, opioids can be divided into:-1. Opioid agonists These have only agonistic action on opioid receptors. Drugs are:1. Natural:- Morphine, codeine.2. Semisynthetic:- diacetylmorphine Heroin, pholcodeine, hydromorphone, oxymorphone, hydrocodone, oxycodone.3. Synthetic:- Pethidine mepridine, fentanyl, methadone, dextropropoxyphene, tramadol, sulfentanil, alfentanil, remifentanil, levorphenol, dextromoramide, dipipanone.2. Complex action opioid and opioid antagonists. Relatively minor changes in the structure of an opioid can convert a drug that is primarily an agonist into one with antagonistic actions at one or more types of opioid receptors. Drugs are:1. Agonist-antagonists k analgesics - Nalorphine, Pentazocine, Butorphenol.2. Partialweak p agonist k antagonist - Buprenorphine.3. Pure antagonists - Naloxone, Naltrexone, Nalmefene.Nature of interaction of opioid ligands with the three major typesof opioid receptors, along with equivalent analgesic dosesLigandm muk kappad deltaAnalgesic dose mg1. MorphineAgo. StAgo. WAgo. W102. NalorphineAnta. StAgo. M--3. PentazocineP. Ago., Anta. WAgo. M-30-604. ButorphanolP. Ago. WAgo. St-1-35. BuprenorphineP. Ago.Anta. M-0-3-0-46. NaloxoneAnta. StAnta. MAnta. W-7. NaltrexoneAnta. StAnta. MAnta. W-8. MetLeu enkephalinAgo. M-Ago. St-9. b-EndorphinAgo. St-Ago. St-10. Dynorphin A, BAgo. WAgo. StAgo. W- 