The role of drugs in countering adverse pathophysiological profiles: influence on hemodynamics

Metabolic effects of manidipine

The calcium channel antagonists (CCAs) were originally introduced as vasodilators for the treatment of coronary heart disease, but are now also noted for their clinical efficacy in the management of hypertension. Data from large clinical studies have shown that CCAs are not associated with the undesirable metabolic effects (e.g. worsening of dyslipidemia and reduction of insulin sensitivity) seen with older agents such as thiazide diuretics and beta-adrenoceptor antagonists (beta-blockers) that are used to treat hypertension. Indeed, reductions in cardiovascular risk and rates of onset of new cases of diabetes mellitus have been reported in trials in patients with hypertension treated with CCAs. These beneficial effects extend beyond those expected to accompany reductions in BP. Until recently, the biochemical effects underlying these metabolic changes were only poorly understood, but pharmacologic studies have now started to shed more light on these issues. Of particular interest are studies with manidipine, some of which suggest that this agent may be associated with greater improvements in insulin sensitivity and may have better renal protective properties than other CCAs. Confirmation of potential differences among CCAs in terms of the relative magnitude of any beneficial metabolic effects requires further study. Ongoing research is expected to clarify further the action of these agents at the cellular level and to assist with the optimization of antihypertensive therapy, particularly in patients with elevated cardiovascular risk profiles.

Renin-angiotensin-system blockade in the prevention of diabetes

Type 2 diabetes often occurs in association with hypertension and cardiovascular disease, and markedly increases cardiovascular risk. Strategies to reduce the incidence of diabetes in patients with cardiovascular disease or at high risk for such disease are therefore important. Certain classes of antihypertensive agents, namely the thiazide diuretics and beta-blockers, have an adverse impact on the metabolic profile and increase the risk for new-onset diabetes in hypertensive subjects. In contrast, angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs), which are blockers of the renin-angiotensin system (RAS), have been shown to increase insulin sensitivity. They may also reduce the risk of diabetes in patients with hypertension or cardiovascular disorders. Some of the evidence in favour of ACE inhibitors and ARBs has come from studies with active comparators that have potential adverse metabolic effects. However, the Candesartan in Heart failure-Assessment of Reduction in Mortality and morbidity (CHARM) programme demonstrated that the ARB candesartan reduced the incidence of diabetes in heart failure patients in comparison to placebo. The mechanisms responsible for the beneficial effects of RAS blockade remain to be established. Nevertheless, a treatment that can control hypertension and reduce the risk of onset of type 2 diabetes at the same time is certainly desirable.

New-onset diabetes and antihypertensive drugs

Observational studies have provided evidence that a consistent fraction (approximately 15-20%) of hypertensive patients displays a glucose intolerance state that may be aggravated by antihypertensive drug regimens based on thiazide diuretics or beta-blockers. This review examines the relative and absolute diabetogenic effects of antihypertensive drugs, by comparing the impact of 'new' (calcium antagonists, angiotensin-converting enzyme inhibitors and angiotensin II receptor antagonists) versus 'old' (diuretics and beta-blockers) drugs on new-onset diabetes in recent clinical trials. Evidence is provided that compared with diuretics and beta-blockers, new-onset diabetes is less common with 'new' drugs, and that conventional antihypertensive compounds, particularly when combined together, may amplify the natural time-dependent tendency towards the development of this metabolic disease. This paper provides new insights into the potential mechanisms responsible for the phenomenon and the clinical significance of antihypertensive drug-induced diabetes.