Etorphine (M99) is a semi-synthetic opioid possessing an analgesic potency approximately 1,000–3,000 times that of morphine. It was first prepared in 1960 from oripavine, which does not generally occur in opium poppy extract but rather in "poppy straw" and in the related plants Papaver orientale and Papaver bracteatum. It was later reproduced in 1963 by a research group at MacFarlan Smith in Gorgie, Edinburgh, led by Professor Kenneth Bentley. It can also be produced from thebaine.

Etorphine (M99) is a semi-synthetic opioid possessing an analgesic potency approximately 1,000–3,000 times that of morphine. It was first prepared in 1960 from oripavine, which does not generally occur in opium poppy extract but rather in "poppy straw" and in the related plants Papaver orientale and Papaver bracteatum. It was later reproduced in 1963 by a research group at MacFarlan Smith in Gorgie, Edinburgh, led by Professor Kenneth Bentley. It can also be produced from thebaine.