Help me understand something...

[resorcinol]

Lets use methadone and oxymorphone in this example.

Methadone over a certain dosage would block oxymorphone from binding the u receptors right?

Why then, is oxymorphone more potent mg for mg, if its ability to attatch to the receptor is less?

What determens affinity (which drug gets the receptor) vs potency (dose needed for equianalgesic effect)?

See what I'm asking... where i'm confused...

[Indy]

Affinity and potency are different. Potency is how much it activates the receptor when it's attached. Affinity is how strongly it attaches compared to other opiates. Affinity is like how strong a magnet's pull is, but with the receptor. Potency is how well it makes sweet love to that receptor when it's attached.

[roxi*stardust]

In simple terms, the Methadone molecule is very large so it takes a bit longer to "squeeze" into the receptors but once it does it does not leave as fast either because of it's size. It fills the whole receptor so nothing else can get in.