Which class is NOT considered a secondary anti-hypertensive agent?

The β2 agonist is not considered a secondary anti-hypertensive agent because it primarily functions as a bronchodilator and has limited effectiveness in managing hypertension. Its primary role is in treating conditions like asthma or chronic obstructive pulmonary disease (COPD) by relaxing bronchial smooth muscle, rather than directly addressing elevated blood pressure.

In contrast, other classes, such as α1 antagonists, direct arterial vasodilators, and centrally acting α2 agonists, are specifically designed to manage hypertension. α1 antagonists work by blocking sympathetic vasoconstriction, leading to vasodilation and a reduction in blood pressure. Direct arterial vasodilators, like hydralazine, act directly on the smooth muscle of the arteries, causing them to relax, thereby lowering blood pressure. Centrally acting α2 agonists, such as clonidine, function by decreasing sympathetic outflow from the central nervous system, which also helps in lowering blood pressure.

Thus, while β2 agonists play an important role in respiratory conditions, their mechanism of action does not directly target hypertension, differentiating them from the other classes listed.