Haemodynamic profile of captopril treatment in various forms of hypertension

Dose finding studies with imidapril--a new ACE inhibitor

1. We describe an approach involving a smaller, shorter study, leading onto a longer, larger study in which the antihypertensive effects of ascending doses of imidapril, a new ACE inhibitor, were investigated. Both studies were planned prospectively, assuming a clinically useful fall in BP to be 8 mm Hg (s.d. = 9). The studies included patients with mild to moderate essential hypertension (baseline sitting diastolic blood pressure (SDBP) 95-115 mm Hg). After a placebo run-in of 2-3 weeks patients received either placebo or imidapril 2.5, 5, 10 or 20 mg in the 2 week study (n = 91) or imidapril 5, 10, 20 or 40 mg in the 4 week study (n = 162). 2. The overall mean baseline SDBP was 103.4 mm Hg (s.d. 0.62) in the initial study and 101.5 mm Hg (s.d. 0.41) in the 4 week study. 3. Compared with placebo, imidapril 10, 20 and 40 mg significantly reduced SDBP. There was no significant difference between these doses, suggesting that 10 mg achieved maximal ACE inhibition in most patients. The 2.5 mg dose showed no significant effect. The 5 mg dose gave an intermediate effect. In both studies the overall incidence of adverse events was similar in the imidapril and placebo groups, and was not worrying.

Treatment of essential hypertension today. The role of beta blockers, calcium antagonists, and ACE inhibitors

The greater sensitivity of echocardiography than electrocardiography has revealed left ventricular hypertrophy (LVH) to occur in a significant minority of patients with systemic hypertension, with the exact prevalence dependent both on how a population is selected and on the sex. race, and possibly age composition of its members. LVH is more closely related to blood pressure recorded in the patient's natural setting during normal activity or exercise--whether measured by portable recorder or home manometer--than to blood pressure measured by the physician. A subgroup of patients with mild essential hypertension exhibit high cardiac output and evidence of supernormal myocardial contractility in the absence of LVH; whereas amongst patients with more sustained hypertension, LVH may be either concentric (associated with high ejection fractions) or eccentric (associated with abnormal responses to exercise). Recent data indicate that echocardiographic detection of LVH identifies mildly hypertensive patients at significant risk, a finding that may aid identification of patients for drug treatment.

Effect of captopril on renal haemodynamics and the renin-angiotensin-aldosterone and osmoregulatory systems in essential hypertension

The effect of captopril on renal plasma flow (RPF), glomerular filtration rate (GFR), plasma concentrations of renin, angiotensin II (Ang II), aldosterone (Aldo) and arginine vasopressin (AVP), serum osmolality (Sosm), free water clearance (CLH2O), fractional urinary excretion of electrolytes and blood pressure (BP), was examined in 10 patients with moderate essential hypertension. Placebo plus furosemide was given for 6 weeks, followed by a 6-week period on captopril and furosemide. The renin-angiotensin-aldosterone system was partly blocked by captopril, resulting in a 18% fall in BP. GFR was reduced by 8% during captopril treatment, whereas RPF remained unchanged. Water loading-induced suppression of Ang II and AVP was inhibited by captopril therapy. Without affecting BP in the placebo period, water loading almost abolished the captopril-induced reduction in BP. It is concluded that non-acute captopril treatment of moderates essential hypertension reduces GFR slightly, possibly by producing dilatation of efferent arterioles. The antipressor effect of captopril is lessened during volume expansion, which may be secondary to reduced activity of the renin-angiotensin-aldosterone and osmoregulatory systems.

Splint renal function after captopril in unilateral renal artery stenosis

The renal extraction ratios of 131I-sodium iodohippurate (131I-Hippuran) and 125I-thalamate were greatly reduced on the affected side by 50 mg captopril in seven out of 14 patients with unilateral renal artery stenosis. With long term captopril 150 mg daily the uptake of 99mTc-diethylenetriaminepenta-acetic acid by the affected kidney, which was determined by scintillation camera renography, became almost zero in these seven patients, indicating severe reduction of the glomerular filtration rate. Function of the affected kidney returned on discontinuing treatment. The reduced extraction of sodium iodohippurate probably reflected a shortened plasma transit time through the kidney due to intrarenal vasodilatation. The reduced extraction of thalamate reflected a low filtration fraction, suggesting that the vasodilatation was, at least in part, at the level of the postglomerular arterioles. Captopril had little effect on the contralateral kidney and on the kidneys of 17 patients with essential hypertension, and serum creatinine concentrations showed minor changes. Radioisotope renography should be performed after beginning captopril treatment in patients with renal artery stenosis. This is also recommended for patients given captopril as a third line drug when renal artery stenosis has not been excluded. Hypertension is these patients is often severe and difficult to control. Renal artery disease is not rare in this difficult group and finding seriously impaired renal function on one side during captopril treatment may be diagnostic.

The renin-angiotensin system during converting enzyme inhibition with captopril in patients with severe treatment-resistant hypertension

The effect of captopril on blood pressure (BP) and various components of the renin-angiotensin system was assessed in ten severely hypertensive patients. Captopril acutely reduced the BP with a maximum decrease of 23% at 90-120 min. Maintenance treatment with captopril alone could not control the BP in any of the patients. Addition of hydrochlorothiazide markedly reduced the BP, while supplementation with propranolol caused no consistent changes. Three patients attained a supine diastolic blood pressure (SDBP) less than or equal to 90 mmHg. Only two patients had a fall in SDBP less than 10 mmHg. One patient stopped because of taste disturbances. Monitoring the renin-angiotensin system showed suppressed plasma concentrations of angiotensin II and increased levels of angiotensin I and renin, indicating the inhibition of converting enzyme activity. Plasma concentration of renin substrate decreased significantly. This observation has important implications for the methodology of renin assays. Captopril is an effective alternative in the treatment of hypertensive patients not readily controlled with conventional therapy.

Effects of captopril in acute and chronic heart failure. Correlations with plasma levels of noradrenaline, renin, and aldosterone

The angiotensin-converting enzyme inhibitor, captopril, was given to 19 patients with severe heart failure. Seven patients had acute myocardial infarction and the remainder had chronic myocardial damage caused by ischaemia or valvular disease. Cardiac filling pressures were raised in all, the pulmonary capillary "wedge" pressure being 17 mmHg or more. Captopril, 50 mg orally, raised stroke volume and cardiac output, and reduced heart rate, cardiac filling pressures, systemic arterial pressure, and the plasma concentrations of aldosterone and noradrenaline. These changes were attended by clinical improvement. Decrements in cardiac filling pressures, systemic arterial pressure, and total peripheral resistance were positively correlated with pretreatment plasma renin. Long-term treatment with captopril was offered to 14 patients. Four patients with severe coronary disease died suddenly after initial clinical improvement. In nine patients haemodynamic measurements were repeated after three months. The results showed sustained effects on cardiac output and filling pressures but there was no loss of body weight. The haemodynamic effects were at least as good as with previous vasodilators. The fall in systemic arterial pressure, however, was greater with captopril. Captopril may become a valuable adjunct to the treatment of acute and chronic heart failure, but more information about its effect on coronary blood flow is required.