Individualised Selection of Antihypertensive Therapy

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  • Drugs 46 (Supp!. 2): 142-148, 1993 0012-6667/93/0200-0142/$3.50/0 Adis International Limited. All rights reserved.


    Individualised Selection of Antihypertensive Therapy L.H. Opie Medical Research Council Ischaemic Heart Disease Research Unit, University of Cape Town Medical School, Cape Town, South Africa

    Summary Theoretically, it should be possible to match the requirements of individual patients with the pharmacological and clinical properties of the large number of antihypertensive drugs now avail-able. The concept of automatic sequential stepped-care therapy is now largely outdated, but therapy of clinically important hypertension must be initiated with one agent. Diuretics remain a first-line option in the elderly and in Black patients, as do calcium antagonists. Outcome trials are available only for the elderly, and in these the benefits of initial diuretic therapy are well docu-mented. Nonetheless, diuretics may often need to be co-prescribed with a i3-blocker or an adren-ergic modifier such as methyldopa. i3-Blockers are preferred in patients with ischaemic heart disease or enhanced adrenergic drive, while a-blockers are preferred in patients with blood lipid abnormalities or prostatic problems. Calcium antagonists or angiotensin converting enzyme (ACE) inhibitors are being increasingly used as initial therapy when quality of life is important and metabolic neutrality is required.

    Calcium antagonists are more likely to be effective first-line therapy than ACE inhibitors in patients with a high salt intake, in patients with Raynaud's disease, when angina pectoris is present, and in Black patients. ACE inhibitors are preferred for combination with diuretic agents, and in the presence of congestive heart failure or low salt intake. Experimentally, both calcium antagonists and ACE inhibitors can prevent ischaemic ventricular fibrillation and atheroma. Combination therapy between these 2 drug classes is gaining increasing acceptance because of these theoretical advantages. The clinical role of these agents, both singly and in combination, can only be fully evaluated by large scale outcome studies, which are now required.

    Currently, the selection of antihypertensive therapy appears to be based on at least 5 factors. These include 1) experience (communal or indi-vidual), 2) comparative outcome studies, 3) sur-rogate end-points, 4) quality-of-life parameters and adverse effects of the agent used, and 5) indivi-dualised choice-care for the patient.

    1. Clinical Experience

    In the late 1970s, the Joint National American Committee on the Detection, Evaluation and Treatment of High Blood Pressure (1977) recom-

    mended the use of thiazide diuretics as step 1 therapy for hypertension, with step 2 requiring the addition of an adrenergic modifier (propranolol, methyldopa, or reserpine). Step 3 required the ad-dition of the vasodilator hydralazine, and step 4 a ganglion-blocking agent such as guanethidine. None of these recommendations were based on long term comparative outcome studies, and therefore re-flected opinion and clinical practice rather than scientific evidence per se. The following year, the WHO Expert Committee on Arterial Hypertension (1978) suggested that either a ~-blocker or a di-uretic could be used as first-line therapy, with the

  • Individualised Selection of Antihypertensive Therapy

    addition of a vasodilator to (j-blockade or addition of a (j-blocker or other adrenergic modifier to di-uretic therapy being recommended as the second-line approach. Again, these recommendations must have been based on clinical experience and enlight-ened guesswork. Hence previous clinical practice has been largely based on perceived wisdom rather than scientific data.

    2. Comparative Outcome Studies

    More recently, the publication of the first Medi-cal Research Council (MRC) trial (Medical Re-search Council Working Party 1985) made avail-able the results of the first large scale comparative study. In that study, both (j-blockers and diuretics were effective in the reduction of stroke, although diuretics appeared to be more effective. The cor-onary event rate was not reduced by diuretic therapy, but was reduced in nonsmokers receiving a (j-blocker. Thus, some glimmer of logic started to appear - diuretics, a simple treatment, reduced stroke very well, but did not alter coronary events. It should, however, be borne in mind that the di-uretic dose in that study was as high as was then the custom.

    At the same time, Zanchetti (1985) proposed that diuretics, (j-blockers or angiotensin converting en-zyme (ACE) inhibitors be used as first-line therapy for hypertension. Two years later, Zanchetti (1987) had included calcium antagonists as alternative first-line agents. It was not until 1988 that the Joint National Committee (1988) followed the direction of Zanchetti and recommended a variety of agents as first-line treatments for hypertension. Even more recently, the Fifth Joint National Committee (1993) has bowed to logic and added a-blockers and a-(j-blockers as one of 6 possible alternative therapies.

    Thus, what individual experience had estab-lished in the mid-1980s, i.e. that almost any anti-hypertensive drug could be used as fust-line treat-ment, has now been officially recommended. Nonethekss, it must be remembered that these rec-ommendations have not been based on large scale comparative outcome studies. The MRC trial did no more than compare 2 of the many possible first-


    line therapies. Furthermore, almost all trials un-dertaken to date can be severely criticised. The overall impression given by the results from the 2 MRC trials, the first on middle-aged mildly hy-pertensive subjects (Medical Research Council 1985) and the second on elderly hypertensive sub-jects (Medical Research Council 1992), is that first-line treatment with diuretics produces a more fa-vourable outcome than first-line treatment with fJ-blockade.

    In another comparative study, the Metoprolol Atherosclerosis Prevention in Hypertensives (MAPHY) Study, the (j-blocker metoprolol was compared with diuretic treatment over 4 years (Wikstrand et al. 1988). Metoprolol and a high dose of thiazide diuretic (hydrochlorothiazide 50mg) gave identical control of blood pressure, with lower total mortality in the group of patients receiving metoprolo1, because of fewer deaths from coronary heart disease and stroke. In contrast to the earlier MRC trial (Medical Research Council Working Party on Mild to Moderate Hypertension 1981), which used the (j-blocker propranolol, the MAPHY Study used a cardioselective (j-blocker and found the benefit of (j-blockade was largely found in smokers. The major problem with the MAPHY Study was the absence of a placebo group. There-fore, the apparent reduction in coronary mortality in patients receiving metopro101 could have been attributable to an excess mortality in the group not treated by metoprolol, possibly as a result of smok-ing and diuretic therapy.

    3. Clinical Trials Evaluating Surrogate End-Points 3.1 Left Ventricular Hypertrophy

    Now that left ventricular hypertrophy (L VH) has been identified as an independent risk factor for cardiova~ular mortality, interest in control of L VB has increased (Levy et al. 1990). Furthermore, the widespread availability of echocardiography with absolute quantification ofleft ventricular mass has also stirred interest in L VH as a surrogate end-point. In a ,meta-analysis of 109 studies, Dahlof et al. (1992a), demonstrated reversal of LVH with fJ-

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    blockers, calcium antagonists and ACE inhibitors, but found that the most effective agents were the ACE inhibitors. Diuretics also appeared to be ef-fective, but predominantly reduced ventricular di-ameter rather than ventricular wall thickness, thereby achieving only pseudo-regression of L VH.

    In a subsequent prospective double-blind study, Dahlof et al. (1992b) examined the effects of 6 months' treatment with either enalapril or hydro-chlorothiazide. Patients who did not respond to monotherapy were excluded from the analysis. En-alapril reduced blood pressure chiefly through a re-duction in total peripheral resistance, while hydro-chlorothiazide reduced blood pressure primarily through a reduction in cardiac output. Left ven-tricular mass and wall thickness decreased more significantly in patients treated with enalapril than in those receiving hydrochlorothiazide. Fundal changes were significantly improved only in patients receiving enalapril. The results of this trial appear to suggest that reversal of cardiac hypertro-phy is related more closely to changes in the renin-angiotensin-aldosterone system than to the abso-lute blood pressure reduction.

    3.2 Blood Lipid Patterns

    There has been a single study comparing the effects of a diuretic, a l'1-blocker, an aI-blocker, a calcium antagonist, and an ACE inhibitor on blood lipid levels in patients with mild hypertension. In reality, patients included in this trial were virtually normotensive, with an average initial blood pres-sure of 140/91mm Hg. Many of the patients would not have fulfilled the primary criteria of many clin-icians for antihypertensive therapy. The decline in blood pressure in all treated groups was similar. Total cholesterol and high density lipoprotein (HDL) cholesterol tended to fall in all groups ex-cept in the group of patients receiving diuretic therapy. Compared with all the other groups, tne increase in total cholesterol with the diuretic chlor-thalidone was statistically significant (p < 0.01). This trial is of interest because the diuretic dose used was deliberately low (chlorthalidone 15 mg! day), confirming the clinical impression that di-

    Drugs 46 (Suppl. 2) 1993

    uretic therapy may adversely affect total blood cholesterol levels. Of the other drugs studie