Two very common terms in pharmacology and the pharmacy world in general are pharmacodynamics and pharmacokinetics. The best way I have been taught these terms is by the following:
- Pharmacodynamics – what the drug does to the body
- Pharmacokinetics – what the body does to the drug
So using buprenorphine as my example, I want to tackle pharmacodynamics. The pharmacodynamics of this medication is that it partially stimulates mu receptors with high affinity.
Affinity is how “tightly” a drug is bound to a receptor. The high affinity explains why it may be useful in the management of addiction. It can help prevent other opioids (full agonists) like morphine, fentanyl etc. from binding and giving a typical full mu agonist effect.
Because it partially stimulates (also known as a partial agonist), you do get some opioid activity which explains why it is a controlled substance. This partial stimulation can work to help prevent withdrawal. What you must remember is that these effects are dose dependent!
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What do we think about patients on chronic buprenorphine patch (Butrans) for pain who also receive hydrocodone/apap (Norco) or another full opiate agonists?