Pharmacokinetic aspects

Pharmacokinetic aspects

All three catecholamines are rather polar, due to both the hydroxyl groups and the amino group, which will be mostly protonated at physiological pH. They will thus not cross the blood brain barrier easily, so that in effect the cate-cholamine pools in the brain and in the periphery will not interfere with each other. Exclusion by the blood brain bar-rier also applies to many synthetic agonists and antagonists that act on catecholamine receptors, as these compounds often are structurally similar to the physiological media-tors. These drugs are useful to influence the peripheral.