Opiate receptors affinity binding

Heroin (diacetylmorphine) a highly lipophilic drug but has very weak or no affinity for opiate receptors. It penetrates the brain rapidly whereupon it is metabolised to morphine which then binds to the mu receptor. 

Pharmacology Buprenorphine is a semisynthetic centrally acting opioid analgesic derived from thebaine a 0.3 mg dose is approximately equivalent to 10 mg morphine in analgesic effects. Buprenorphine exerts its analgesic effect via high affinity binding of CNS opiate receptors. 

Buprenorphine is a semi-synthetic, partial mu-agonist, highly lipophilic, opioid drug. Because it is a partial agonist, when buprenorphine competes with morphine or heroin for mu-receptors it can reduce their maximum effect. Buprenorphine binds strongly to mu and kappa opiate receptors it associates with the mu-receptor slowly (30 minutes), but with high affinity, low intrinsic activity and slow and incomplete dissociation. The slow dissociation from the receptor probably limits the intensity of withdrawal by preventing the rapid... 

PCP binds strongly to a specific receptor present in synaptic membranes from rat brain, less strongly to muscarinic receptors, and weakly to /u,-opiate receptors.(26) The specific binding affinity of a variety of PCP analogs with substituents in the homo- and heterocyclic moieties have been examined but no data on their analgesic properties are yet available.<27)... 

Narcotic antagonists have higher affinity to the opiate receptor site than the narcotic analgesic, resulting in blocking the narcotic analgesic from binding to the opiate receptor site. 

A series of analogs of the benzomorphans were prepared in which the amino group is exocyclic (99 and 100) (401). In contrast to the benzomorphans and other rigid opiates, the receptor binding of (99) and its analogs exhibits almost no stereoselectivity [K- (jit) = 2.0 and 2.2 nAf for the (+) and (-) isomers] in vivo, both isomers of (99) were inactive. Racemic (100) exhibits an almost 10-fold increase in K-receptor affinity (K = 6.6 nAQ compared to that of the isomers of (99) while retaining nanomolar affinity for ix receptors = 2.0 nM) this compound is a full k agonist in vivo. 

The relative binding affinities of the optical isomers of methadone, a-methadol, a-acetylmethadol and their N-demethylated derivatives to the opiate receptors of rat brain confirmed the agonistic nature of this series of drugs.144... 

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