Vascular reactivity: a measurement of calcium channel blockade.

Clinical studies have shown that calcium antagonist drugs interfere with the reactivity of vascular smooth muscle and thereby attenuate the pressor responses to adrenergic and non-adrenergic vasoconstrictor agents. It is, therefore, possible to explore the extent and duration of calcium channel blockade by studying the magnitude and time course of the attenuation of pressor responses. The effects of three long-acting calcium antagonists, amlodipine, lacidipine and nifedipine GITS (gastrointestinal therapeutic system), on vascular reactivity were assessed over 24h and 48h dosage intervals. It was shown that all three agents attenuate the vasoconstrictor responses to both adrenergic and non-adrenergic stimuli. However, amlodipine and nifedipine GITS were found to suppress vascular reactivity more consistently than lacidipine over 24h. Extending the analysis to 48h after dosing showed that amlodipine had the most consistent effect.