Apart from the aforementioned variables, a number of biological or life-style factors can contribute to the development of resistant hypertension. Several classes of pharmacological agents can produce transient or persistent increases in BP (37) (Table 3). Nonsteroidal anti-inflammatory drugs (NSAIDs) are a common cause of worsening BP control. They increase BP by an average of 5 mm Hg, in part because of inhibition of renal prostaglandin production decreases in renal blood flow, followed by sodium and fluid retention (38). They also interfere with BP-lowering of all antihypertensive drug classes except calcium antagonists (39- 40). The effect of NSAIDs on BP is more pronounced in patients with reduced kidney function (13). Selective cyclo-oxygenase-2 inhibitors have effects similar to those of NSAIDs on BP control (41). Sympathomimetic agents (nasal decongestants, anorectic pills, cocaine, amphetamine-like stimulants), oral contraceptives, glucocorticoids, anabolic steroids, erythropoietin, and cyclosporine are also commonly used agents that can interfere with BP control. Black licorice, included in some oral tobacco products, and herbal supplements (e.g., ma huang and ginseng), also raise BP (12- 13,16). The effect of these agents varies; most people manifest little or no effect, but certain persons may experience severe BP elevations. Lastly, illicit drugs can be a major unappreciated cause of resistant hypertension. Agents such as steroids and cocaine are common causes of resistant hypertension.