Dihydropyridine calcium antagonists and the trough: peak ratio

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Effects of shorter-acting calcium antagonists The antihypertensive effect of the dihydropyridine calcium antagonists is highly correlated with the drug plasma concentration. These agents reduce blood pressure primarily via arteriolar vasodilation. More rapidly absorbed formulations such as the nifedipine capsule quickly produce a marked fall in blood pressure which tends to provoke a reflex increase in sympathetic nervous activity via the baroreceptor mechanism. These shorter-acting formulations are therefore more likely to be associated with vasodilatory side-effects such as flushing, palpitations, ankle edema, headaches and dizziness.

Advantages of longer-acting agents: The link between pharmacokinetics, pharmacodynamics and side effects becomes more evident when longer-acting agents such as nifedipine gastrointestinal therapeutic system (GITS) and amlodipine are examined. These drugs have a trough:peak ratio that approaches 1, and thus exert a uniform antihypertensive effect over the dose interval. They are associated with fewer side effects in consequence of less baroreceptor reflex stimulation. The net result is improved efficacy and greater patient tolerability of these compounds.

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