I'm a med student, and yes, of course it would. Methadone is dissolved in the plasma, and as such when you take some of that plasma away some of the methadone goes away aswell. However, it isn't relevant, because it is the concentration of the methadone in the plasma that is relevant to how much it affects your brain, not the overall amount in the plasma. Also, some will remain in all the tissues in your body, e.g bound to receptors in your brain.
Haha I love the US! Crack heads can donate but <snip> can't.