Changing concepts in the management of hypertension

Influence of sodium intake on hydrochlorothiazide-induced changes in blood pressure, serum electrolytes, renin and aldosterone in essential hypertension

To determine the influence of dietary sodium intake on the effects of hydrochlorothiazide (HCT) on blood pressure (BP), serum electrolytes, renin and aldosterone, nine male patients with uncomplicated essential hypertension were studied during the following therapeutic regimes: 1) sodium restriction alone (50 mmol/day), 2) sodium restriction combined with HCT (50 MG TWICE DAILY), 3) HCT alone, and 4) sodium restriction combined with HCT. Low sodium diet alone and HCT alone lowered BP to the same extent. The combination of HCT and sodium restriction had no extra effect on supine BP, but elicited complaints of dizziness and weakness in each patient, and overt orthostatic hypotension in three cases. Sodium restriction during HCT treatment caused hyponatraemia and aggravated hypokalaemia. Hyponatraemia could not be accounted for solely by changes in cumulative sodium balance. Plasma renin concentration rose markedly during the combined treatment. Plasma aldosterone was normal during HCT alone, but elevated when HCT was combined with sodium restriction. These results cast some doubt on the therapeutic value of prescribing a low sodium diet to patients with essential hypertension treated with thiazide diuretics. Overactivity of the renin-angiotensin-aldosterone system during this regime might explain both the lack of a beneficial effect on BP and the adverse influence on serum potassium.

Interaction of clonidine and beta-blockers

On the hypothesis that non-selective beta-blockers can antagonize or reverse the antihypertensive effect of clonidine (C), 12 hypertensive outpatients were treated with C alone and in combination with propranolol (P), atenolol (A) and prazosin (Pz). C alone (0.11 or 0.22 mg b.i.d.) or in combination with P (80 mg b.i.d.) did not provide normotension. Changing P to A (50 mg b.i.d.) reduced supine systolic and diastolic pressures, which now were significantly lower (p less than 0.01) than during C alone. Changing A to P again resulted in elevated pressures. Pz (1 mg t.i.d.) added to the C+P regimen lowered supine blood pressures to the levels otherwise recorded during C+A. C dose-dependently contracted rabbit aortic spiral in vitro, reaching about 50% of maximum responses to noradrenaline. Pz abolished this response. P (0.1--10 micrograms/ml) but not A somewhat enhanced responses to high doses of C. Sotalol rather antagonized C contractions. We conclude that A but not P enhances the antihypertensive action of C. No hypertensive interaction was observed.

Vasodilator drugs in the treatment of hypertension

Vasodilator drugs counteract the major haemodynamic abnormality of hypertension, namely, arteriolar constriction. As a group, they tend to cause tachycardia and fluid retention, but these side-effects are variable within the group. Vasodilator drugs are effective in the treatment of the whole range of hypertensive diseases, from severe refractory hypertension to mild hypertension. With increasing recognition of the necessity of treatment in mild asymptomatic hypertension, those vasodilator drugs which can be used on their own, such as prazosin and calcium antagonists, are attractive as initial therapy, because they do not have adverse effects on the levels of atherogenic lipids and other risk factors for vascular disease. The major current use of vasodilator drugs in combination with a thiazide and a beta-adrenoreceptor-blocking drug is in the treatment of moderate-to-severe hypertension.

Long-term experience with the combination of clonidine and beta-adrenoceptor blocking agents in hypertension

The risk of cardiovascular and fatal complications and the antihypertensive effect of a clonidine-beta-blocker combination was studied in 98 patients and was compared with the results for a group of patients treated with other antihypertensive regimens. The profile of complications was similar in the two groups for a total follow-up period of more than 2000 treatment-months. Clonidine in combination either with propranolol or atenolol had a distinct antihypertensive effect. However, clonidine plus atenolol resulted in a more immediate and pronounced fall in blood pressure. It is concluded that the combination of clonidine and a beta-blocker is an effective antihypertensive medication, and that patients treated with it are apparently at no greater risk of serious cardiovascular incidents than are those treated with other regimens.

Beta-adrenergic receptor blocking drugs in hypertension. With special reference to their use as initial therapy

Beta-adrenergic receptor blocking agents have been receiving attention as first-line agents for the treatment of hypertension. However, a number of significant side effects of these drugs have been brought to light. The most important of these--increases in "atherogenic" lipid concentrations--may place treated persons at risk of coronary artery disease and myocardial infarction. Other side effects, including bronchospasm, heart failure, cold extremities, reduced insulin secretion and central nervous system effects, may preclude their use in many patients. However, because several major trials have shown that controlling blood pressure reduces the incidence of coronary heart disease and stroke, the use of antihypertensive therapy is likely to increase and to continue for longer periods. The physician must prescribe an agent with the fewest and most minor side effects. Alternatives to beta-blocking drugs, such as the alpha-receptor blocking agent prazosin, should be considered and evaluated because of the limiting side effect profile of beta blockers.

Sodium intake, blood pressure and red cell sodium efflux

A series of studies have been undertaken correlating sodium intake, blood pressure and red cell 22Na efflux. The results for male and female patients differ. In male patients with elevated blood pressure, increased sodium intake caused a rise in blood pressure and a fall in red cell 22Na efflux rate. In female patients the results were variable and while certain females followed the above pattern, others had the converse response. Evidence is presented that the change in red cell 22Na efflux is due to a factor in plasma that inhibits the ouabain sensitive component of sodium efflux. This increases after acute and chronic sodium loading and may be similar to natriuretic factor described previously. It is postulated that increased sodium intake causes hypertension by producing a humoral factor that inhibits sodium transport out of cells and that this alters the calcium content of muscle cells and increases their contractility and thus produces hypertension.

Low salt diet and frusemide in the treatment of hypertension

The BPs of 86 of 100 severely hypertensive patients were controlled by measures designed to reduce total body sodium, namely a low salt diet plus the addition of incrementally increased frusemide treatment if diet alone was inadequate. Control of hypertension was maintained over prolonged periods of time in 70 of the patients. Among the 14 who failed to respond adequately, mean plasma renin level was higher (when tested) than in those who did respond adequately, and renal artery stenosis was discovered in 2. Supplementary propranolol controlled the hypertension in 8 of the inadequate responders.

A comparison between once-daily and twice-daily administration of metoprolol in the management of hypertension

The efficacy of metoprolol as an antihypertensive agent was assessed in 20 previously untreated Asian patients with mild to moderate hypertension. After a 4-week run-in period when placebo therapy was given, the patients were given oral metoprolol at a starting dosage of 100 mg twice daily. The dosage of metoprolol was increased at fortnightly intervals until either satisfactory blood pressure control, defined as a diastolic blood pressure of less than 90 mmHg or a greater than 10% fall in pre-treatment diastolic blood pressure, was achieved or a total of 400 mg metoprolol was reached. All 20 patients had satisfactory control of their blood pressures on a twice-daily regimen and the average dosage of metoprolol required was 200 mg daily. For the second part of the study, the medication was changed to a once-daily regimen at the same total dosage of metoprolol. Final efficacy of once-daily therapy was assessed after 8 weeks of treatment. All blood pressure and pulse rate reductions were significant (P < 0.001) from the placebo phase. However, twice-daily and once-daily readings were not significantly different from each other. No side-effects were reported during the study.

Results from a multicentre trial of metoprolol and a study of hypertensive patients with chronic obstructive lung disease

Ninety-nine patients took part in a multicentre, long-term study of metoprolol in the treatment of hypertension. Significant reductions in blood pressure and heart rate were achieved by the use of metoprolol alone, or in combination with other antihypertensive agents. Side effects were similar to those seen with other beta-adrenergic blocking agents, except that bronchospasm and cold extremities were rarely encountered. Results of monitoring for the abnormal eye symptoms and antinuclear factor titre are discussed. In a second study, 14 hypertensive patients with asthma (11 patients) or history thereof (three patients), received metoprolol for their hypertension. In general, no significant change in forced expiratory volume in one second (FEV1) was found, despite significant reduction in blood pressure and heart rate. The concomitant use of a beta2-agonist is discussed.

Hypertension treated by salt restriction

31 patients with a diastolic blood-pressure between 95 and 109 mm Hg have been treated for two years with a regimen involving a moderate restriction of salt in the diet. The results are compared with those in a control group and in a drug-treated group. Salt restriction has reduced the diastolic blood-pressure by 7.3+/-1.6 mm Hg, a result similar to that in patients treated with antihypertensive drugs. In the untreated group the diastolic blood-pressure rose by 1.8+/-1.1 mm Hg. Most patients did not achieve the desired amount of salt restriction and a stricter adherence to the diet might have caused further falls in blood-pressure. Excessive salt intake is probably a major cause of the epidemic of hypertension in "civilised" countries and a reduction in salt intake may help to control the epidemic. In persons with a diastolic blood-pressure between 90 and 105 mm Hg salt restriction should be tried before drugs.

Treatment of hypertension successively with a diuretic, clonidine or a beta-blocking agent and hydralazine

The present study was carried out in an homogenous group of 49 untreated hypertensive patients, all aged 45 years. Diastolic blood pressure was equal to or greater than 110 mmHg in successive measurements; eleven patients were classified as WHO group II, and the others as WHO group I. An initial placebo period of 3 weeks was followed by cyclothiazide medication with a good response in 6 patients. The remaining patients were given either clonidine or practolol, and by adjustment of the dose a good response was obtained in 31 patients. In these cases the treatment was exchanged after 6 weeks. The antihypertensive effect of relatively small doses of clonidine was equal to that of practolol. Since completion of the study practolol has been withdrawn because of the emergence of long term toxic effects. In 12 cases, hydralazine had to be added to obtain a satisfactory response. Mild side-effects were common, especially at the beginning of clonidine treatment, but they did not necessitate discontinuation of treatment. Further comparative studies of clonidine and beta-blockers should be carried out and more experience with the combination of clonidine and vasodilators in the treatment of hypertension is necessary.

Current status of treatment of severe hypertension

Drug fashions have changed and older drugs have given place to others with less side effects. Drugs and combinations of drugs administered to 100 patients currently under treatment at a clinic for severe hypertensives are listed. The most popular drugs were thiazide diuretics, methyldopa, beta-adrenergic blocking drugs, clinidine and hydrallazine. A thiazide diuretic was a constant member of the drug combinations. About 60% of patients achieved "good" blood pressure control (diastolic blood pressure less than or equal to 100 mm Hg), 30% "fair" (diastolic blood pressure=100 to 110 mm Hg) and 10+ "poor" (diastolic blood pressure greater than 110 mm Hg). Similar proportions were in "good", "fair" and "poor" general health. The best prospect for improved management of hypertension probably lies in earlier treatment with current drug combinations.