Samuel J. Mann, MD, is professor of clinical medicine, Hypertension Division, Weill/Cornell Medical School, New York Presbyterian Hospital, New York.

The article by Rehman and colleagues (page 27) offers two important observations about the control of hypertension in African American men. The first is that at both Veterans Affairs (VA) and non-VA sites, blood pressure control rates for African Americans were lower than those for whites, despite the same or a greater number of medications being prescribed. The second major finding is that the control rate of hypertension for African Americans was better at VA sites than at non-VA sites, whereas for whites, the control rate was the same at both sites. The former finding is consistent with recent findings in the National Health and Nutrition Examination Survey, which also showed that blood pressure was less well controlled in African Americans, even though they were prescribed more medication.¹ This is actually not that surprising, as studies have consistently indicated that not only hypertension, but also resistant hypertension, occurs more frequently among African Americans than among whites.²

Issues surrounding the use of diuretics
In discussing resistant hypertension in African Americans, although much of the focus has been on access to care, cost, and compliance, important insights can be gained by considering the effect of selection and dosing of drugs, and, in particular, of diuretics, which are the drugs of choice for treating hypertensive African Americans. In this article, in both VA and non-VA settings, African Americans were more likely than whites to be taking a diuretic and less likely to be taking a beta blocking agent. This is reassuring, as diuretics have been widely reported to be more effective than beta blocking agents in African American patients. It is disturbing, however, that only 63% were taking a diuretic, even though over 50% had blood pressures above the target level. It would be interesting to ascertain the proportion of uncontrolled hy­pertensive patients who were not given a diuretic.

Another important issue that was not addressed by the study is the issue of drug dose, particularly the dose of the diuretic prescribed. The most widely prescribed dose of hydrochlorothiazide is 25 mg. Yet, in the Anti­hypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT), it was 25 mg of chlorthalidone, not hydro­chlorothiazide, that was used and found to be at least as effective as an angiotensin-converting enzyme inhibitor or calcium channel blocking agent.³ It is time to recognize that 25 mg of hydrochlorothiazide is inadequate for many African American pa­tients with resistant hypertension, and in many cases, represents undertreatment. It is less effective than 25 mg of chlorthalidone; 37.5 to 50 mg of hydro­chloro­thiazide is needed for an equivalent effect.⁴ Of course, doses of hydro­chloro­thiazide higher than 25 mg, as well as the 25-mg dose of chlor­thalidone, are associated with a significant incidence of hypok­ale­mia. Combining 25 to 50 mg of hydro­chlorothiazide with either spironolactone (Aldactone) or amiloride (Mi­damor) can substantially increase the antihypertensive effect while substantially reducing the occurrence of hypokalemia.

Cost of medication
The second major finding was that control of hypertension in African Americans was better at VA sites than at non-VA sites. The authors made the important observation that African Americans were prescribed more medication at non-VA sites than they were at VA sites, which does not indicate less aggressive prescribing by non-VA physicians as a cause of the difference. It suggests instead that non-VA pa­tients were less likely to be taking their medication, possibly indicating cost issues in non-VA settings. Like­wise, the smaller number of visits at non-VA sites could also be attributed to cost issues or to awkwardness about not taking the medication. Also suggesting that the problem is economic rather than behavioral, at VA sites, African Americans were as likely as whites to be compliant with follow-up visits.

The article dramatically underlines the importance of cost as one of the barriers to hypertension control. It also tells us that factors other than cost are evident and that suboptimal prescribing patterns must be ad­dressed to further reduce the high rate of resistant hypertension among Afri­can Americans. To accomplish this will require not only the use of a di­uretic in a greater proportion of hypertensive African Americans, but also an increase in the response rate to diuretic treatment by either using chlo­r­thalidone (up to 25 mg) or hydro­chlorothiazide at a dose of 25 to 50 mg combined with an aldosterone-antagonizing agent in a greater proportion of those with resistant hypertension. Furthermore, as indicated by the results of this study, the lower cost of diuretics provides yet another reason to include a diuretic in the regimen of nearly every African American pa­tient with resistant hypertension.

References
1. Hertz RP, Unger AN, Cornell JA, et al. Racial disparities in hypertension prevalence, awareness, and management. Arch Intern Med. 2005;165(18):2098-2104.

2. Cooper R, Rotimi C. Hypertension in blacks. Am J Hypertens. 1997;10(7 pt 1):804-812.

3. ALLHAT Officers and Coordinators for the ALLHAT Collaborative Research Group. The Antihypertensive and Lipid-Low­er­ing Treatment to Prevent Heart Attack Trial (ALLHAT). Major outcomes in high-risk hypertensive patients randomized to angiotensin-converting enzyme inhibitor or calcium channel blocker vs diuretic: the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT). JAMA. 2002;288(23):2981-2997.

4. Carter BL, Ernst ME, Cohen JD. Hy­drochlorothiazide versus chlorthalidone: evidence supporting their interchangeability. Hypertension. 2004;43(1):4-9.