Effects of different sodium intakes on the antihypertensive and renal effects of single oral doses of nifedipine in hypertensive patients

The aim of this study was to investigate whether the antihypertensive and renal effects of Ca2+ antagonists are related to the sodium state of the patients. For this purpose, in a group of 11 patients with essential hypertension we have compared the blood pressure lowering effects of a single oral dose of nifedipine before (100 mmol Na+/day and 40 mmol K+/day) and after sodium depletion (20 mmol Na+/day and 40 mmol K+/day: each period was of 6-8 day duration). During the normal sodium diet nifedipine significantly lowered supine blood pressure (from 185 +/- 13/107 +/- 7 to 161 +/- 13/100 +/- 7 mm Hg, p less than 0.001) and induced a significant rise in Na+ excretion (from 52 +/- 10 to 94 +/- 13 mmol/6 h) and in urine volume (from 520 +/- 80 to 947 +/- 120 ml/6 h; p less than 0.01). Sodium depletion significantly lowered supine blood pressure (152 +/- 12/95 +/- 9 mm Hg, p less than 0.001); nifedipine caused a further and significant blood pressure reduction (142 +/- 11/90 +/- 8 mm Hg, p less than 0.01), but only a minor and not significant increase in sodium excretion (from 10 +/- 2 to 22 +/- 5 mmol/6 h) and urine volume (from 338 +/- 76 to 463 +/- 94 ml/6 h). Our data suggest that the natriuretic action of calcium antagonists is not relevant to their antihypertensive effect.