The Bentley Compounds
Etorphine (Fact Overview)
Discovered in the early 1960's.
Effects similar to morphine. Analgesia, catatonia, constipation, respiratory depression, initial excitement, and sedation.
Takes effect within minutes of injection, peaks after 15 to 30 minutes. Analgesia and sedation last 30 to 60 minutes in animals.
Produces euphoria & reward. Presumed to have a high abuse & addiction liability in humans.
Very effective as a painkiller. 1,000 to 4,000x more potent than morphine as an analgesic, depending upon the clinical setting. A dose of 0.0025 to 0.01 mg (or 2.5ug to 10ug i.e. micrograms) would be roughly as active as 10mg morphine by injection. Lethal dose for an adult human will range from 30ug to 120ug.
One of the least subtype-selective opioid agonists in use.
High affinity for mu and kappa receptors, moderate affinity for delta receptor; agonist at all three.
Also referred to as 'M-99' or Immobilon in the veterinary setting. Used on large game animals as a tranquilizer and anaesthetic.
Because of its potency, M-99 is always supplied alongside its antidote, diprenorphine (or Revivon), an ultra potent opiate antagonist, and also a bentley compound. In case of human exposure, diprenorphine reverses an overdose.
International legislation barred etorphine for use in humans unfortunately. Its 7,8 dihydro derivative is currently used in humans, and is several times more potent. John Lewis, a former researcher with Bentley, has speculated that etorphine may have had success as a human product, had it been marketed differently:
|Immobilon (i.e. Etorphine Hydrochloride)|
Dihydroetorphine (Fact Overview)
Ultra potent opioid agonist. Reletatively selective for the mu receptor, with high affinity and efficacy. 1,000 to 12,000x more potent than morphine and 2 to 13x more potent than etorphine, depending on the method of measure.
Elimination half life of 30-40 minutes (~38min); analgesia lasts 1-2 hours depending on ROA and dose - requiring dosing intervals of 1 to 3 hours when given in its traditional form.
Used as an analgesic in humans in China. Like bupe, DHE is poorly absorbed orally. It is given by injection, sublingual or buccally, or transdermally. Sublingual doses of 20 to 180 ug are fully analgesic and produce relatively mild side effects. DHE in a long acting transdermal patch has been shown to relieve pain for up to 32 hours with minimal side effects.
Produced potent reward & reinforcement in studies, but is believed to produce a lesser ratio of euphoria to analgesia than does morphine or heroin. Though it is obviously a more potent euphoriant than morphine by weight, it may carry a lower addiction liability in equivalent doses.
Reportedly has been used in opiate substitution therapy, with positive results.
Available in sublingual tablets of 20ug or 40ug. Or as solution for injection containing 20ug/ml dihydroetorphine hydrochloride. Transdermal patches available (dose range??)
In 1966, researchers had synthesized a compound which was reserved the name M6029. M6029 was an N-subtituted orvinol which would later become known as buprenorphine (i.e. bupe). Bupe was a typical bentley opioid, similar in structure to etorphine, but was substituted with a nitrogen-cyclopropylmethyl as opposed to the methyl. None the less, it produced potent antinociceptive effects, 33x stronger than morphine.
As it turned out, the CPM group of bupe created a mixed agonist antagonist - with partial agonist activity at the mu receptor, antagonist activity at the kappa receptor. Unlike other mixed agonist antagonists at the time, buprenorphine produced no dysphoria - while drugs such as pentazocine and butorphanol were agonists at the kappa receptor and thus likely to produce dysphoria, bupe was an antagonist at kappa receptors.