A Cross-over Trial to Identify Patient Characteristics That Predict Blood Pressure Response to Antihypertensive Therapy in General Practice

Population-wide elimination of hypertension would reduce the incidence of all stroke, MI and heart failure with 30 to 50% and contribute to a reduction of between 25 to 50% of the total mortality related to these cardiovascular conditions. However, despite increasing numbers of antihypertensive medication prescriptions, hypertension control rates are still insufficient.

The current study will focus on improving the success rate of the initial treatment of hypertension. The individual response to antihypertensive drugs varies between individuals: many patients responding well to one drug respond poorly to another. We hypothesize this difference in response to depend on the presence of certain characteristics of patients, like waist circumference, age and gender.

The major objective of our study will be to identify patient characteristics that predict the efficacy of different classes of antihypertensive drugs. Despite pleas in international publications to tailor antihypertensive treatment on individual basis, until now patient characteristics are not taken into account in the medical treatment of hypertension. We will address our study objective by the use of a PRospective, Open label (medication not blind), Blinded End-point crossover design (PROBE) in which 100 general practice based, newly diagnosed hypertensive patients, aged 18 - 65 years will be included to be treated with a diuretic and an angiotensin receptor blocker (ARB). Each patient will be treated with standard doses of both medications consecutively. Treatment duration for each medication will be four weeks, with a four weeks washout period in between. The choice for a diuretic versus an ARB is based on the substantial difference in working mechanism representing the two major determinants of blood pressure: effect on intravascular volume (diuretic) or vascular tone (ARB). Blood pressures will be assessed with both 24 hour-monitoring and practice based standardized measurements.

Twenty-three different patient characteristics will be studied and were selected based on review of literature and pathophysiologic theory. These characteristics will be (1) simple anthropometric measures like body mass index and fat distribution, (2) demographic characteristics, such as gender or ethnicity or (3) disease characteristics such as baseline diastolic and systolic blood pressure, co-morbidity and blood plasma levels of easily measured bioactive compounds, like renin and B-type natriuretic peptide.

The primary outcome measure will be the difference in blood pressure response between both study drugs; secondary outcome measures will be the difference in the number of patients achieving target blood pressure and the number of adverse drug events.