Initial dose of enalapril in hypertension

Changes in the renin-angiotensin-aldosterone axis in later life

The renin-angiotensin-aldosterone system (RAAS) is one of the main systems involved in the regulation of blood pressure and sodium homeostasis. In animal experiments and in humans, the plasma renin activity and aldosterone levels are reduced with aging. The age-related differences in plasma renin activity and aldosterone are more pronounced in stimulated conditions (when sitting in an upright position, when salt intake is restricted and when plasma volume is depleted) than under basal conditions. Age-related alterations of the kidney (glomerulosclerosis, decreased number of functional nephrons) might account for the age-related differences in the active to inactive plasma renin ratio. In the same way, a diminished synthesis of angiotensinogen by the liver could contribute to the decrease in the activity of the RAAS in aging. This is partially compensated for by increases in the density of angiotensin II receptors reported in elderly patients. Furthermore, aging is associated with a reduced adrenal responsiveness to angiotensin II, contributing to lower production of aldosterone and alterations of sodium homeostasis. Estradiol and progesterone help stimulate the secretion of renin. Reduced levels of these hormones at menopause also lead to reduced plasma renin activity. In relation to these findings, several studies have shown that reductions in blood pressure, induced by short or long term treatment with angiotensin converting enzyme (ACE) inhibitors, were more pronounced in old than young hypertensive patients. An insertion/deletion polymorphism in the ACE gene has been described; the genotype deletion/deletion of this gene has been reported to be closely associated with longevity. This result was unexpected since the same deletion polymorphism was also shown to represent a potent risk factor for myocardial infarction.

Responses to low dose intravenous perindoprilat infusion in salt deplete/salt replete normotensive volunteers

1. Intravenous ACE inhibitor therapy appears to have a role in the treatment of acute heart failure and early after myocardial infarction. Practical experience with intravenous administration with activation of renin is limited. We report responses to perindoprilat (Pt, 0.67 mg) or placebo (P) infused over 4 h in normotensive male volunteers (n = 12, 19-28 years, 53-77 kg) with double-blind, placebo controlled salt depletion (SD) or salt repletion (SR) as a model of the activated renin system. 2. Salt depletion caused no significant fall in serum sodium (P, 139.4 +/- 2.4; Pt, 138.3 +/- 1.9) compared with salt replete preparation (P, 139.9 +/- 1.2; Pt, 139.7 +/- 0.9) but elevation of plasma renin activity 2-3-fold. Pretreatment baseline systolic blood pressure following salt depletion (P, 121 +/- 9.3/71 +/- 7.9; Pt, 121.5 +/- 9.6/69 +/- 8.1) was higher than following salt replete preparation (P, 114 +/- 9.5/61 +/- 7.2; Pt, 116.9 +/- 6.9/67 +/- 7.2). 3. Baseline corrected supine SBP fell significantly and to a similar extent following active treatment regardless of activation of the renin system (SD, -14.6 +/- 9.5/-9.4 +/- 6.4; SR, -12 +/- 14/-10.1 +/- 6.6) compared with placebo (SD, -6.1 +/- 6/-3.7 +/- 5.6; SR, -4.7 +/- 10/-1.3 +/- 6.5). Heart rate was unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of age on the pharmacokinetics and pharmacodynamics of single oral doses of benazepril and enalapril

1. Eighteen healthy, normotensive subjects (nine young and nine elderly) participated in a double-blind, 3-way, crossover study to compare aspects of the pharmacokinetics and pharmacodynamics of single oral doses of 10 mg benazepril, 10 mg enalapril and placebo. 2. The hypotensive effect was similar after both drugs but the absolute reductions were greater in the elderly who had higher initial levels of blood pressure. 3. The AUCs for both benazeprilat and enalaprilat were higher in the elderly but by a significantly greater amount for enalaprilat (+ 113% vs 40%; P < 0.01). 4. The AUCs for both drugs tended to be highest in subjects with the lowest creatinine clearance. 5. The changes in kinetics and dynamics observed in the elderly after benazepril are qualitatively similar to those with other ACE inhibitors. The clinical significance of the quantitative differences requires further investigation.

Aldactazine/captopril combination, safe and effective in mild to moderate systemic hypertension: report on a multicenter study of 967 patients

The safety and efficacy of a thiazide/potassium-sparing diuretic and an angiotensin-converting enzyme inhibitor used concomitantly was evaluated in a large, multicenter study. Aldactazine was administered alone for 2 months, after which time captopril was added in those whose blood pressure had not normalized (332 patients). At the end of the 6-month study, control of blood pressure was achieved in 88% of the patients with one or the other regimen. No clinically significant changes were recorded for a number of biologic parameters. Specifically, there was 1 case of hyperkalemia (6 mmol/liter), a very low incidence of hypotension (1.6%), and a low rate of adverse effects. Therefore, such a combination could provide important therapeutic benefits in hypertensive patients.

Adherence and its management in clinical trials: implications for arthritis treatment trials

Adherence in clinical trials is a consistent problem regardless of the disease process or organ system under investigation. In this paper data and examples from clinical trials examining cardiovascular diseases are used as the basis for a review of various adherence principles. Issues reviewed include: the importance of adherence in clinical trials, an overall program for adherence in clinical trials, and specific issues in adherence from arthritis clinical trials. Special attention is given to a program for the prevention of reduced adherence for participants of a clinical trial as well as acute and chronic intervention plans for those with good adherence and those with reduced adherence in a clinical trial.

Angiotensin-converting enzyme inhibitors in the elderly

Although early studies suggested little role for angiotensin-converting enzyme (ACE) inhibitors in older hypertensive patients, more careful evaluation has confirmed their efficacy and good tolerability. Although the elderly tend to have low plasma renin levels, the fall in blood pressure after ACE inhibitors is at least as great (and in several studies greater) than in younger age groups. Because several ACE inhibitors, including captopril and enalaprilat, are eliminated by the kidneys, there are predictable age-related effects on pharmacokinetics. Reduced renal clearance will contribute, at least in part, to the enhanced intensity and duration of action seen in elderly patients. However, not all the effects of age on the kinetics and dynamics of ACE inhibitors are predictable. Studies with perindopril and benazepril in the elderly confirm the efficacy of this group of drugs but highlight other pharmacokinetic differences. ACE inhibitors are effective in reducing blood pressure and can be considered for wider use in elderly hypertensives.

Drug interactions that matter. A critical reappraisal

Drug interactions are ubiquitous but those with proven clinical relevance are much less common. Only when the combined effects of the interacting drugs are greater or less than the arithmetic sum of their individual actions can the event be considered a true interaction. This eliminates many candidate 'interactions' which in reality merely describe the summation of similar or opposing, but independent, drug effects. An appreciation of those drug interactions that really do matter can be best achieved by combining a practical knowledge of the pharmacological mechanisms involved with awareness of the most vulnerable patients (those with little reserve capacity) and the drugs associated with the greatest risk (those with a narrow therapeutic index). This review follows these guidelines and provides an account of well documented drug interactions categorised according to mechanism.

Ramipril for hypertension secondary to renal artery stenosis. Changes in blood pressure, the renin-angiotensin system and total and divided renal function

The converting enzyme inhibitor, ramipril, 20 mg once daily, was given to 3 hypertensive patients with unilateral renovascular disease. At 1 month, 24 hours after the last dose of ramipril, blood pressure, plasma angiotensin II and converting enzyme activity remained low, and active renin and angiotensin I high. There was no tendency for converting enzyme inhibition to be overcome during 1 month of ramipril therapy. Ramipril caused slight increases in serum potassium and urea, no change in serum creatinine and no consistent changes in the renal vein renin ratio. Ramipril caused little change in renal plasma flow on the stenotic side, but filtration fraction was reduced in 2 patients. There was no serious deterioration in total or individual glomerular filtration rate during ramipril therapy. The drug was well tolerated and there were no serious side effects. Ramipril, given once daily, is likely to be effective in controlling hypertension with renal artery stenosis.

Comparison of enalapril and bendrofluazide for treatment of systemic hypertension

The antihypertensive and biochemical effects of the angiotensin-converting enzyme inhibitor enalapril were compared with those of the thiazide diuretic bendrofluazide. Patients with untreated mild to moderate essential hypertension were entered into a randomized, double-blind, double-dummy, parallel-group study. Blood pressure (BP) decreased significantly (p less than 0.001) with either drug therapy: from 172/103 to 147/87 mm Hg (n = 18) with enalapril and from 179/104 to 165/95 mm Hg (n = 22) with bendrofluazide; thus, enalapril produced a greater reduction (p less than 0.05) than bendrofluazide. The median dose of enalapril was 20 mg/day (range 10 to 40) and that of bendrofluazide was 5 mg/day (range 2.5 to 10). Both drugs reduced serum sodium levels by small amounts. This was significant only for enalapril (decrease of 1.3 mmol/liter, p less than 0.05). Hyponatremia was not seen in any patient. Three patients were withdrawn from each treatment group due to adverse effects, although both drugs were generally well tolerated.

Antihypertensive effect of single doses of enalapril in hypertensive patients treated with bendrofluazide

This study was designed to investigate the validity of the then current recommendations for initiation of therapy with enalapril in hypertensive patients on treatment with a diuretic. Enalapril in single doses of 10 and 20 mg was given to 13 hypertensive patients on treatment with bendrofluazide 5 mg daily in a randomised, crossover, placebo controlled study. The mean maximal reduction in blood pressure was similar with both doses (35/20 mmHg supine, 38/20 mmHg standing), occurred on average within 6 h of tablet ingestion, and was not accompanied by any significant change in heart rate. Three patients experienced symptomatic hypotension. In one patient this was incapacitating after 10 mg and precluded exposure to 20 mg. This study shows that in hypertensive patients receiving treatment with diuretics, the addition of enalapril should be undertaken with caution. An optimal starting dose of enalapril in such patients remains to be confirmed.

Enalapril. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic use in hypertension and congestive heart failure

Enalapril maleate is an orally active angiotensin-converting enzyme inhibitor. It lowers peripheral vascular resistance without causing an increase in heart rate. Enalapril 10 to 40 mg/day administered either once or twice daily is effective in lowering blood pressure in all grades of essential and renovascular hypertension, and shows similar efficacy to usual therapeutic dosages of hydrochlorothiazide, beta-blockers (propranolol, atenolol and metoprolol) and captopril. Most patients achieve adequate blood pressure control on enalapril alone or with hydrochlorothiazide. In patients with severe congestive heart failure resistant to conventional therapy, enalapril improves cardiac performance by a reduction in both preload and afterload, and improves clinical status long term. Enalapril appears to be well tolerated, with few serious adverse effects being reported. It does not induce the bradycardia associated with beta-blockers or the adverse effects of diuretics on some laboratory values. In fact, the hypokalaemic effect of hydrochlorothiazide is attenuated by the addition of enalapril. The incidence of the main (but rare) side effects of hypotension in hypovolaemic patients and reduced renal function in certain patients with renovascular hypertension, which are also seen with captopril, might be reduced by careful dosage titration, discontinuation of diuretics, and monitoring of at-risk patients. Thus, enalapril is a particularly worthwhile addition to the antihypertensive armamentarium, as an alternative for treatment of all grades of essential and renovascular hypertension. It also shows promise in the treatment of congestive heart failure.