Bentley compounds are a class of semi-synthetic opioids that were first synthesized from thebaine

Thebaine

Thebaine , its name coming from the Greek Θῆβαι, Thēbai, an ancient city in Upper Egypt, is an opiate alkaloid. A minor constituent of opium, thebaine is chemically similar to both morphine and codeine, but has stimulatory rather than depressant effects, causing convulsions similar to strychnine...

 by K. W. Bentley. The compounds include: oxycodone

Oxycodone

Oxycodone is an opioid analgesic medication synthesized from opium-derived thebaine. It was developed in 1916 in Germany, as one of several new semi-synthetic opioids in an attempt to improve on the existing opioids: morphine, diacetylmorphine , and codeine.Oxycodone oral medications are generally...

, oxymorphone

Oxymorphone

Oxymorphone or 14-Hydroxydihydromorphinone is a powerful semi-synthetic opioid analgesic first developed in Germany circa 1914, patented in the USA by Endo Pharmaceuticals in 1955 and introduced to the United States market in January 1959 and other countries around the same time...

, nalbuphine

Nalbuphine

Nalbuphine is a semi-synthetic opioid used commercially as an analgesic under a variety of trade names, including Nubain. It is noteworthy in part for the fact that at low dosages, it is found much more effective by women than by men, and may even increase pain in men, leading to its...

, naloxone

Naloxone

Naloxone is an opioid antagonist drug developed by Sankyo in the 1960s. Naloxone is a drug used to counter the effects of opiate overdose, for example heroin or morphine overdose. Naloxone is specifically used to counteract life-threatening depression of the central nervous system and respiratory...

, naltrexone

Naltrexone

Naltrexone is an opioid receptor antagonist used primarily in the management of alcohol dependence and opioid dependence. It is marketed in generic form as its hydrochloride salt, naltrexone hydrochloride, and marketed under the trade names Revia and Depade...

, buprenorphine

Buprenorphine

Buprenorphine is a semi-synthetic opioid that is used...

 and etorphine

Etorphine

Etorphine is a semi-synthetic opioid possessing an analgesic potency approximately 200 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 related plants, Papaver orientale and Papaver...

. They represent the first series of more potent μ-opioid

Mu Opioid receptor

The μ-opioid receptors are a class of opioid receptors with high affinity for enkephalins and beta-endorphin but low affinity for dynorphins. They are also referred to as μ opioid peptide receptors. The prototypical μ receptor agonist is the opium alkaloid morphine; μ refers to morphine...

 agonists, with some compounds in the series being over 1000 times the potency of morphine as an analgesic. The latter was then used in veterinarian

Veterinarian

A veterinary physician, colloquially called a vet, shortened from veterinarian or veterinary surgeon , is a professional who treats disease, disorder and injury in animals....

 medicine as a narcotic for elephants and other large animals.

The true "bentley compounds" are properly known as the orvinols, and include a series of bridged oripavine derivatives which can be manufactured with thebaine or oripavine itself. The trademark of these compounds is the presence of a 6,14 endoetheno bridge and their substitution at carbon position 7.

Oxycodone, oxymorphone, naloxone, or nalbuphine do not possess either of these characteristics and were not discovered by K. W. Bentley or Reckitt Research Group; Oxymorphone and oxycodone are in the codeinone/morphinone class, while naloxone is a non-bridged thebaine derivative. Nalbuphine is a morphinan class mixed agonist/antagonist.