F Is for Fuck-Up

Tanya says that etorphine is "something like a kajillion times stronger than morphine". Etorphine a semi-synthetic opioid used to tranquilize large animals, depending on route of administration (subcutaneous/intramuscular/intravenous), it is roughly 1,000-3,000 times more potent than morphine, 200-600 times more potent than heroin, and 10-30 times more potent than fentanyl. It was developed in 1960 from oripavine, an alkaloid which does not generally occur in opium poppy (Papaver somniferum) extract, but rather the related plants Papaver orientale (Oriental poppy) and Papaver bracteatum (Iranian poppy). Etorphine is only approved for use in veterinary medicine, since its normal doses for large animals: 10-15 mg for an African elephant, 5-10 mg for an Indian elephant, and 2-4 mg for a black rhino, would be highly toxic and many times the fatal dose for a human. Etorphine's median lethal dose in humans is only 3 micrograms, or 0.003 milligrams, which is smaller than a single grain of salt, since it is lethal to humans etorphine is always packaged with a potent opioid antagonist called diprenorphine that reverses etorphine's effects, in case of accidental human exposure, but it's most often used to reverse the drug's effect on animals. Since the late 1990's the use of etorphine has largely been phased out due to the development of an extremely potent analog of fentanyl called carfentanil, at 10 times the potency of etorphine, and 10,000 times the potency of morphine, it is one of the most potent opioids synthesized. Carfentanil has become favored over etorphine for tranquilizing large animals (especially agitated animals) because fentanyl and its analogs have a rapid onset of action, etorphine can take up to 15-20 minutes to take full effect, but carfentanil can take effect in under five minutes. Carfentanil also wears off much more quickly, and often doesn't require the administration of a second drug to reverse its effects the way etorphine often does; if the animal needs to be sedated for a longer period, carfentanil can be administered along with a long-acting tranquilizer like acepromazine.

Dexter initially chooses Etorphine as his tranquilizer of choice for his victims and at one point says "one milligram of this will knock a racehorse out for hours." Etorphine is explicitly disallowed for human use as its LD50 (lethal dose for 50% of test subjects) is THREE micrograms, 3/1000ths of a milligram.

Correction: In the original series Dexter mentions using an extremely diluted dose of Etorphine to subdue his victims, a dose that small would be easy to make with access to a forensics lab. Etorphine (M99) also always comes packaged with diprenorphine (M5050), an antidote for etorphine, that he uses to reverse its effects.