BP that remains elevated (above goal) despite admin of an optimal three-drug regimen that includes a diuretic. most common causes are poor compliance, excessive ethanol intake, concomitant conditions (diabetes, obesity, hyperaldosteronism, high salt intake, and/or metabolic syndrome), concomitant medications( sympathomimetics, nonsteroidal anti-inflammatory drugs, or antidepressant medications), insufficient dose and/or drugs, and use of drugs with similar mechanisms of action