Long-term morbidity and mortality trials with amlodipine

The Use of Calcium Antagonists in the Therapy of Hypertension in the Elderly

Calcium antagonists (calcium channel blockers) are widely used in the treatment of hypertension and other cardiovascular diseases. The results of a large number of clinical trials have demonstrated that calcium antagonists are as efficacious as other classes of antihypertensive agents in decreasing blood pressure in the elderly patients. Large clinical trials have shown the effectiveness of calcium antagonists (with long duration of action) in reducing cardiovascular and cerebrovascular morbidity and mortality in elderly hypertensive patients. The calcium antagonists are a chemically, pharmacologically and therapeutically heterogeneous group of agents. Among themselves, they differ in vasoselectivity, effect on cardiac conduction, sympathetic activation, adverse effect profile, ability to protect against target organ damage, suitability for patients with co-morbid conditions, and pharmacodynamic characteristics. The calcium antagonists can be used as single agents or in combination with other antihypertensive drugs. These drugs should not be used as first-line drugs in treating high blood pressure in patients with heart failure, since drugs in other classes provide more benefits. The dihydropyridine calcium antagonists should not be used in post-myocardial infarction patients or in patients with unstable angina; however, non-dihydropyridines may be used in such patients. The adverse effects of dihydropyridines include peripheral and ankle edema, flushing and headache. The short-acting preparations of the older calcium antagonists are no longer used, because of the potential for adverse cardiovascular outcome.

Effects of the calcium channel blocker amlodipine on serum and aortic cholesterol, lipid peroxidation, antioxidant status and aortic histology in cholesterol-fed rabbits

Reactive oxygen metabolites and oxidized fatty acids are proinflammatory and are involved in the pathophysiology of atherosclerosis. Amlodipine, a unique third-generation dihydropyridine-type calcium channel blocker, seems to exert atheroprotective effects through its antioxidant properties related to its chemical structure and independent of its calcium channel-blocking effect. In this study, the interactions of amlodipine with major cellular antioxidants were investigated in order to elucidate the mechanisms underlying its atheroprotective effects. New Zealand white male rabbits were fed regular chow (group 1), chow with 1% cholesterol (group 2), regular chow plus 5 mg/kg/day amlodipine per os (group 3) and 1% cholesterol plus amlodipine (group 4) for 8 weeks. Total cholesterol, malondialdehyde (MDA) and vitamin E concentrations and catalase and superoxide dismutase (SOD) activities were determined in blood drawn before and after the experimental period. Aortic tissue was examined for atherosclerotic changes and aortic total cholesterol, MDA, catalase and SOD were determined. At the end of the 8-week treatment period, serum total cholesterol and plasma MDA were elevated in groups 2 and 4. In group 2, serum vitamin E and plasma SOD diminished (p < 0.05) and catalase increased (p < 0.05). In group 4, SOD activity increased at the end of treatment. MDA levels were lower and plasma SOD activities were higher in group 4 than in group 2. Aortic tissue investigations revealed higher total cholesterol and MDA concentrations and catalase activities in group 2 than in group 4, and the highest tissue SOD activity was recorded in group 4 (p < 0.05 for all comparisons). Morphological examination of aortic tissues exhibited endothelial disarrangement and lipid deposition in group 2. Histopathological alterations related to atherogenesis were less in group 4 than in group 2. Amlodipine seems to exert atheroprotective effects by reducing aortic cholesterol accumulation and blood and aortic lipid peroxidation, enhancing SOD activity both in blood and aortic tissue and suppressing the consumption of vitamin E. On the other hand, the suppression of catalase activity in blood and the aorta interferes with the drug's well-known antioxidant effects.

Arterial calcification: a review of mechanisms, animal models, and the prospects for therapy

The causes of arterial calcification are beginning to be elucidated. Macrophages, mast cells, and smooth muscle cells are the primary cells implicated in this process. The roles of a variety of bone-related proteins including bone morphogenetic protein-2 (BMP-2), matrix Gla protein (MGP), osteoprotegerin (OPG), osteopontin, and osteonectin in regulating arterial calcification are reviewed. Animals lacking MGP, OPG, smad6, carbonic anhydrase isoenzyme II, fibrillin-1, and klotho gene product develop varying extents of arterial calcification. Hyperlipidemia, vitamin D, nicotine, and warfarin, alone or in various combinations, produce arterial calcification in animal models. MGP has recently been discovered to be an inhibitor of bone morphogenetic protein-2, the principal osteogenic growth factor. Many of the forces that induce arterial calcification may act by disrupting the essential post-translational modification of MGP, allowing BMP-2 to induce mineralization. MGP requires gamma-carboxylation before it is functional, and this process uses vitamin K as an essential cofactor. Vitamin K deficiency, drugs that act as vitamin K antagonists, and oxidant stress are forces that could prevent the formation of GLA residues on MGP. The potential role of arterial apoptosis in calcification is discussed. Potential therapeutic options to limit the rate of arterial calcification are summarized.

Rational pharmacotherapy of hypertension in the elderly: analysis of the choice and dosage of drugs

OBJECTIVES

To determine in older people with uncomplicated hypertension: (a) the pattern of prescribing of antihypertensives; (b) the extent of physicians' adherence to recommendations on dosage for antihypertensive combinations; (c) whether prescribing practice conforms with recommended therapeutic guidelines; and (d) the frequency of prescribing of other drugs which have the potential to alter the efficacy of antihypertensive agents.

METHODS

A survey of prescribing in older patients with uncomplicated hypertension in primary care setting of Bahrain was conducted.

RESULTS

Of the 432 (56.5%) patients on monotherapy, 192 (44.4%) were treated with beta-blockers, 87 (20.1%) with calcium channel blockers (CCBs), 53 (12.3%) with alpha-methyldopa, 47 (10.9%) with diuretics, 46 (10.6%) with angiotensin converting enzyme (ACE) inhibitors, and 7 (1.6%) with hydralazine. Of the 1146 patients on mono- or combination therapies, 434 (56.8%) were treated with beta-blockers, 244 (31.9%) with diuretics, 211 (27.6%) with CCBs, 139 (18.2%) with ACE inhibitors, 103 (13.5%) with alpha-methyldopa 8 (1.0%) with brinerdine and 7 (0.9%) with hydralazine. In the 332 (43.5%) patients on combination therapy, 15 different two- and three-antihypertensive drug combinations were prescribed: a diuretic with a beta-blocker (37.2%) and a beta-blocker with either a CCB (20.9%) or an ACE inhibitor (12.4%) were the most popular two-drug regimens. The most commonly prescribed triple drug regimens were a diuretic and a beta-blocker plus either a CCB (26.1%) or an ACE inhibitor (17.4%) and diuretic plus an ACE inhibitor and a CCB (15.2%). Daily dosage of beta-blockers, ACE inhibitors and alpha-methyldopa were somewhat high in a considerable proportion of patients on both mono- and combined therapies. A substantial proportion (9.7%) of patients on monotherapy were treated with immediate release nifedipine.

CONCLUSION

The pharmacotherapy of hypertension in elderly patients was found in some instances not to conform to recommended guidelines. For certain classes of antihypertensive agent such as beta-blockers, ACE inhibitors and alpha-methyldopa, neither the principles of geriatric pharmacology nor of antihypertensive combination therapy, and in particular, the need to reduce daily dosage, were followed. The use of immediate release nifedipine in the elderly is irrational, and instead, the use of long-acting dihydropyridine CCBs should be considered. The results of long-term randomized clinical trials published during the last decade have had a minimal impact on clinical practice of primary care physicians in Bahrain.