Clinical Trial: Optimum Treatment for Drug-Resistant Hypertension

Study Status: Active, not recruiting
Recruit Status: Active, not recruiting
Study Type: Interventional

Official Title: Optimum Treatment for Drug-Resistant Hypertension

Brief Summary:

This study was recommended by NICE, as part of its 2006 guidance for the treatment of hypertension, and is urgently required to provide evidence for the treatment recommendations in patients with resistant hypertension. The study will be a randomised placebo-controlled double-blind crossover comparison of an α-blocker (α), β-blocker (β), and K+-sparing diuretic (∆).

Patients will have a BP at entry above target on ABPM or home monitoring despite supervised administration of maximum tolerated doses of A+C+D. Over 48 weeks they will then receive, in random order either placebo or two doses each of doxazosin (α), bisoprolol (β) or spironolactone (∆). Each treatment cycle will last 12 weeks, with a forced dose-doubling at 6 weeks.

The time course for the study will be similar to study one. 340 patients will provide 90% power, at α=0.01 to detect a 3 mmHg overall difference in home sBP between any one drug and placebo, with spironolactone hypothesized to be best overall. The study will be able to detect a 6 mmHg difference in sBP between each subject's best and second-best drug predicted by tertile of plasma renin, justifying routine use of the measurement in patients with resistant hypertension.

Detailed Summary:

In published surveys throughout the world the majority of patients with hypertension do not achieve target blood pressure. According to most guidelines including NICE, target blood pressure is 130/80 mmHg in patients with diabetes, 140/90 mmHg in other patients. In the UK there are currently at least 3 million people with treated hypertension whose blood pressure is not controlled. A significant number of these patients will have drug resistant hypertension, defined as:

"a blood pressure that is not adequately controlled to recommended treatment targets despite treatment with maximal recommended and tolerated doses of 3 drugs according to the current BHS/NICE guidelines and treatment algorithm, i.e. (*ACE-inhibitor or *ARB or direct renin inhibitor + *CCB + Diuretic (any diuretic except spironolactone), i.e. A+C+D)".

(*where ACE-inhibitor=angiotensin converting enzyme inhibitor, ARB=angiotensin receptor blocker, CCB=calcium channel blocker)

The causes of treatment resistance are unknown, and the choice of fourth-line drug almost entirely empirical. At present there is little comparative data for available drugs. There is considerable evidence pointing to Na+ retention as a common culprit, and some data supporting additional diuretics, or alpha blockade in resistant hypertension, though mainly added to two rather than three drugs.20,29,30 A retrospective analysis of two-drug combinations in trials reported that it makes no difference what is combined with what. 31 However, this conclusion conflicts with the view that drugs for hypertension fall into two main categories, acting respectively on the renin and volume components of hypertension, and that most benefit can be derived from combining drugs from different categories.10,32

We will adopt a hierarchical procedure to test, in order, the differences in home systolic BP between spironolactone and

1. placebo
2. the average of the other two active drugs
3. each of the other two drugs. The second and third tests will be carried out if and only if the preceding test(s) are significant (P<0.05).

We shall use a mixed model to analyse home BP, with unstructured covariances for the repeated measures across the two doses for each treatment within a patient. The model will include terms for gender, age, height, weight, smoking history and a diagnosis of diabetes at baseline. We will also adjust for baseline BP.