The calcium channel-blocking drugs are effective anti-hypertensive agents and enjoy widespread use as single medication or in combination. Their effectiveness is related to a decrease in peripheral resistance accompanied by increases in cardiac index. The magnitude of their effects is determined partly by pretreatment blood pressure levels; maximum blood pressure lowering generally is seen 3 to 4 weeks after the start of treatment. These drugs possess some distinct advantages relative to other vasodilators, including the following:
1. Their relaxant effect on large arteries results in greater compliance, which is beneficial in older persons.
2. Tolerance associated with renal retention of fluid does not occur; an initial natriuretic effect is often observed, especially with the nifedipine group of blockers.
3. They do not have significant effects on the release of renin or cause long-term changes in lipid or glucose metabolism.
4. Postural hypotension, first-dose effect, and rebound phenomenon are not commonly seen.
Their antihypertensive efficacy is comparable to that of p-adrenergic blockers and angiotensin-converting enzyme (ACE) inhibitors. The choice of a calcium channel blocker, especially for combination therapy, is largely influenced by the effect of the drug on cardiac pacemakers and contractility and coexisting diseases, such as angina, asthma, and peripheral vascular disease.
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