The drug for OPD analgesia is:
Alfentanil is a potent but sho-acting synthetic opioid analgesic drug, used for anaesthesia in surgery. It is an analogue of fentanyl with around 1/4 to 1/10 the potency of fentanyl and around 1/3 of the duration of action, but with an onset of effects 4x faster than fentanyl.
Morphine
Pethidine
Fentanyl
Alfentanil
Anesthesia