Phenolic opiate analgesics

In common with other phenolic opiate analgesics, buprenorphine shows low peroral potency, suggesting a high first-pass metabolism effect indeed, work in rats has shown this to be the case. Intravenous studies have estimated that the extraction ratio of buprenorphine is 85% and that peroral systemic availability is consequently expected to be 15% or less. Although absorption from the mouth is slow and, therefore, not as useful as parenteral administration in the treatment of acute pain, it offers a major bioavailability advantage over the peroral route for this drug. If required, the patient can be given a parenteral dose of buprenorphine to achieve rapid pain relief and... 

Catalytic hydrogenation of the hydrolysis product leads to the orally active compound oxycodenone (7-1), which is used in a number of analgesic drugs. Cleavage of the methyl ether to the free phenol leads to one of the most potent close analogues of morphine, oxymorphone (7-2) [5]. Note that both of these compounds carry the hazards of classical opiate dependence liability. 

There is evidence that 3-aryl-3-methylpiperidines closely related to the 4,4-disubstituted piperidines also mimic morphine in their associations with opiate receptors. Again all active derivatives of this type are phenols and some possess antagonist properties when carrying an allyl or CPM substituent at the basic center. N-Methyl derivatives are feeble analgesics but become more... 

Drugs containing phenolic groups include the analgesics morphine (and related opiates) and paracetamol as well as the bronchodilator salbutamol, widely used in the treatment of acute asthma. See Figure 8.9. 

Morphine, C17H19NO3, is a complex phenolic compound whose pentacyclic structure is derived from tyrosine. It is analgesic, narcotic and a powerful respiratory depressant which was previously used iu cough elixirs. Morphine induces euphoria and dependency in some people, anxiety and nausea in others. The central nervous system effects occur through stimulation of specific receptors. Opiate receptors are widely distributed in animals they respond to both endogenous transmitters (peptides) and ingested plant alkaloids. The main receptor types are 8 emotional X. sedative x analgesic a psychotomimetic (Robinson 1986). 

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