Receptor theory of analgesics

Buprenorphine binds slowly to analgesic receptors, but once it does bind, it binds very strongly. As a result, less buprenorphine is required to interact with a certain percentage of analgesic receptors than morphine. 

On the other hand, buprenorphine is only a partial agonist. In other words, it is not very efficient at switching the analgesic receptor on. This means that it is unable to reach the maximum level of analgesia which can be acquired by morphine. 

Overall, buprenorphine s stronger affinity for analgesic receptors outweighs its relatively weak action such that a lower dose of buprenorphine can produce analgesia, compared to morphine. However, if pain levels are high, buprenorphine is unable to counteract the pain and morphine has to be used. 

Nevertheless, buprenorphine provides another example of an opiate analogue where analgesia has been separated from dangerous side-effects. 

It is time to look more closely at the receptor theories relevant to the analgesics. 

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