Enalapril and hydrochlorothiazide as antihypertensive agents in the elderly

Age-related changes affecting atherosclerotic risk. Potential for pharmacological intervention

The incidence of cardiovascular diseases that are related to the atherosclerotic process increases exponentially with age. Organ lesions, the clinical manifestation of atherosclerotic disease, are late events due to complications in the plaque (ulceration, thrombosis, calcification) which are the result of an increased vulnerability to disruption of a previously stable plaque. The higher incidence of age-related clinical events could be explained by a rising sensitivity of plaques to destabilising factors, both parietal and humoral. The increased probability that a plaque in an elderly patient will became vulnerable could be related to those destabilising factors that significantly increase with aging, such as advanced glycation end-products. For these reasons, it seems most important that the analysis of these age-related destabilising factors, rather than those factors that promote the development of early atherosclerotic plaques, should be undertaken. Taking the point of view of a pharmacological intervention, this should eventually lead to a more complete understanding of this process.

Mono- and combination therapy with felodipine or enalapril in elderly patients with systolic hypertension

Using a randomised double-blind crossover design with Latin square allocation of treatments in 20 subjects (7 male, 13 female-ages: 61-87 years) with systolic hypertension, we investigated the efficacy and tolerability of once daily felodipine (extended release) 5-20 mg, enalapril 5-20 mg and their combination compared with placebo in four treatment phases each of 6 weeks duration. During each phase, doses were titrated to achieve a predose clinic supine systolic blood pressure of 140 mmHg or to a predetermined maximum dose. In both the felodipine and combination phases, predose supine and standing systolic and diastolic pressures were significantly reduced compared with the placebo phase (decrease in supine pressure: -13/-5 and -18/-7, respectively). Only predose supine diastolic pressure was significantly reduced (-3 mmHg) compared to placebo in the enalapril phase. In combination the effects of the two drugs on predose blood pressure were additive. There was a 40-60% increase in reported symptoms in the felodipine and combination phases compared with the placebo and enalapril phases. Thus, in elderly subjects with systolic hypertension, felodipine effectively reduces blood pressure throughout the dose interval but with vasodilator adverse effects. In contrast, enalapril is well tolerated but is less effective in reducing blood pressure throughout the whole dose interval.

Which diuretic to use?

The choice of a diuretic depends on knowledge of its efficacy in different disease states as well as the complications associated with its use. However, efficacy of the various diuretic agents as determined in healthy subjects may not always be applicable to the sick patient. The thiazide group appears to be the main offender with regard to hypokalemia and metabolic upsets; these complications seem to stem from long-term use and high dosages. Interest has been expressed on the influence of diuretic induced hypokalemia (and intracellular potassium deficiency) in inducing insulin resistance. The lipid abnormalities may arise as a result of this resistance or may be consequent on hyperinsulinemia from other as yet undetermined mechanisms. In addition, hypertension per se may be associated with insulin resistance. It is interesting to speculate that diuretics, which are commonly used in the treatment of hypertension, may, in some way, perhaps via the induction of hypokalemia, unmask this resistance.

Lisinopril in elderly patients with hypertension. Long term effects on renal and metabolic function

The efficacy and tolerability of lisinopril administered once daily were evaluated in a 12-week open study of 60 elderly patients aged between 65 and 85 years (mean 75 years) with essential hypertension. Mean sitting blood pressure was reduced from 190/106 +/- 6.3/1.3mm Hg (mean +/- SEM) at entry to 162/89 +/- 5.5/0.9 mm Hg after 12 weeks of treatment (p less than 0.001). There was no significant alteration in heart rate, and no occurrence of postural hypotension. The median daily dose of lisinopril was 20mg (range 5 to 40 mg) and only 4 patients required the addition of a diuretic. Mean glomerular filtration rate (GFR) at entry was 61.6 +/- 3.4 ml/min and was unchanged after 12 weeks of therapy. 25 patients continued to receive treatment for 1 year, and 20 of these completed 2 years of treatment. Control of blood pressure was maintained, and heart rate, biochemical parameters and GFR remained unaltered throughout the study. Renal function was preserved and renal blood flow, measured in a group of 14 patients, was significantly increased (p less than 0.025) at the end of the first year after treatment with lisinopril. Thus, in the elderly, lisinopril was well tolerated and highly effective in lowering blood pressure, and renal function was maintained.

ACE inhibitors compared with thiazide diuretics as first-step antihypertensive therapy

While ACE inhibitors are considerably more expensive than thiazide diuretics, they are slightly more effective antihypertensive agents in white patients and have fewer side effects. They can be regarded as suitable first-line therapy in diabetic hypertensives. It is probable that as new drugs in this class are marketed, the price differential will lessen and they will be regarded as acceptable and useful first-line drugs in an increasingly large number of patients.

Hypertension in the elderly

Based on the best evidence we have currently, treating the elderly patient with diastolic hypertension will significantly decrease the risk of stroke. While the evidence for decreasing the risks of coronary disease, congestive heart failure, renal insufficiency, or total mortality is not present, such evidence does exist in younger patients with more severe hypertension. Thus, it is of benefit to reduce the blood pressure in hypertensive older patients. There is some evidence that the elderly may not be more susceptible to side effects of antihypertensive medications than younger populations. However, it is certainly reasonable to attempt blood pressure control by nonpharmacologic means prior to drug treatment. Demographic considerations may affect the choice of medication; in general the stepped-care approach will provide effective management of elevated blood pressure in this population.