Drugs in the management of hypertension. Part I

Haemodynamic profile of captopril treatment in various forms of hypertension

The effects of captopril 450 mg/day for 4 weeks on blood pressure, heart rate, cardiac output and extracellular fluid volume were compared in severe, often drug-resistant hypertension (n = 23), mild to moderate hypertension associated with renal artery stenosis (n = 10) and mild to moderate essential hypertension (n = 20). Plasma renin in the three groups was 52 +/- 19, 58 +/- 17 and 20 +/- 4 microU/ml (mean +/- SEM), respectively. Blood pressure fell by 18 +/- 4%, 21 +/- 2% and 18 +/- 1%. The pressure drop was mainly due to a fall in peripheral vascular resistance. Addition of the diuretic hydrochlorothiazide (25-100 mg/day) caused a further fall in resistance. Despite the vasodilator effect of captopril, reflex cardiostimulation and reactive fluid retention were not observed. In severe hypertension, captopril alone was more effective in lowering blood pressure than combined diuretic-betablocker-vasodilator therapy. Moreover, cardiac output in these patients was higher and resistance was lower after captopril than during combined treatment. Thus, captopril was capable of normalising the abnormal haemodynamic state in patients with essential hypertension, and in hypertension associated with renal artery stenosis. Despite marked differences in pre-treatment plasma renin, the effects of captopril on systemic haemodynamics were similar in all the patients.

Diuretic treatment of resistant hypertension

In patients with hypertension resistant to three or four drugs including a thiazide diuretic substitution of frusemide for the thiazide, or the addition of spironolactone, produced significant reductions in blood pressure and body weight. The response did not depend on the presence of overt fluid retention, renal impairment, or the use of antihypertensive drugs of high potency. Women had larger responses than men. Expansion of the plasma or extracellular fluid volume is an important cause of resistance to treatment even when a thiazide diuretic is used. An increase in diuretic treatment should be tried before using the postganglionic adrenergic blockers or minoxidil in resistant hypertension.

Medical management of hypertension

In a paper like this, with such diverse information, it is impossible to summarize the content completely. Suffice it to say that a stepwise approach to the management of essential hypertension has been presented, beginning with a diuretic agent as the cornerstone of management for most patients. Recommendations for the addition of a second, third, or even a fourth agent have been offered based on a discussion of the site of action of various therapeutic agents. The common side effects and toxicity of various drugs have also been discussed. It cannot be overemphasized that the physician's knowledge of his patient and a thorough understanding of drug actions, interactions, and reactions are mandatory if highly effective, individualized therapeutic programs are to be implemented. Likewise, educating the patient about his disease and eliciting his maximal cooperation are keys to therapeutic success.

Antihypertensive effect of trichlormethiazide in spontaneously hypertensive rats

Antihypertensive and diuretic effects of trichlormethiazide (TCM) were investigated in the spontaneously hypertensive rats (SHR). The antihypertensive effect of TCM in an acute experiment was observed in male SHR only at a dose over 10 mg/kg given intraperitoneally and not in female SHR and normotensive Kyoto Wistar rats. In a subacute experiment (6 weeks), TCM retarded the development of hypertension in the male SHR loaded with 1% saline solution at an oral dose over 1 mg kg-1 day-1 and such had a diuretic effect. Oral administration of TCM and hydrochlorothiazide (HCT) at 10 mg kg-1 day-1 retarded the development of hypertension in the saline loaded female SHR to the same degree, but the relationship between antihypertensive and diuretic effects of both compounds was obscure. Except for decreases of water contents in the thoracic artery and wet weights of hearts, the electrolyte, uric acid, catecholamine and 5-hydroxytryptamine contents in the serum or/and organs were not affected by either TCM or HCT. It is concluded that the antihypertensive effect of TCM and HCT can be observed in SHR with a saline-load, and that the effect may be due to diuretic actions in the male. The relationship was not apparent in female SHR.