Opioid agonist-antagonist is -

Ans. is 'b' i.e., Pantazocine Agonist-antagonists (k analgesics) - Nalorphine, Pentazocine, Butorphenol. Paial/weak agonist + x antagonist - Buprenorphine. Pure antagonists - Naloxone, Naltrexone, Nalmefene. o Clinically agonist - Antagonists and paial/weak agonists are analgesics of comparable efficacy to low doses of morphine and they cause low ceiling respiratory depression, and have lower abuse potential. Impoant points about specific agents. Butorphanol (paial agonist & weak antagonsit, x agonist) o Analgesia and respiratory depression have a lower ceiling. o It causes equivalent analgesia but more sedation than morphine. The most outstanding feature is that butorphanol can neither substiture for nor antagonize morphine --> weak interaction with receptors.