Effects Of A Low-Sodium Diet On Antihypertensive And Natriuretic Responses To Acute Administration Of Nifedipine

This study was designed to determine (1) whether different sodium intakes influence the acute antihypertensive effect of a single dose of nifedipine, (2) whether the combination of nifedipine and a low-sodium diet lowers blood pressure to a greater extent than administration of nifedipine alone and (3) whether a reduction in sodium intake can dissociate the antihypertensive from the natriuretic response to nifedipine. We studied 11 hypertensive patients in order to investigate the antihypertensive and natriuretic effects of a single oral dose of 10 mg nifedipine during sodium repletion (100 mmol/day sodium intake) and depletion (20 mmol/day sodium intake), with a constant potassium intake (40 mmol/day). Nifedipine significantly (P less than 0.01) lowered supine blood pressure, from 178 +/- 14/107 +/- 7 to 161 +/- 12/100 +/- 7 mmHg during sodium repletion and from 152 +/- 12/95 +/- 9 to 142 +/- 11/90 +/- 8 mmHg with sodium depletion. The natriuretic and diuretic actions of nifedipine were marked and statistically significant during sodium repletion and almost absent during sodium depletion. We conclude that (1) the acute antihypertensive effect of a single dose of nifedipine is present both in the sodium-replete and in the sodium-depleted states, although during sodium depletion the nifedipine effect is somewhat reduced in extent and duration; (2) the blood pressure reached after administration of nifedipine in the sodium-depleted state is significantly lower than the values reached after nifedipine treatment in the sodium-replete state; (3) the natriuretic action of calcium antagonists is not essential to the acute antihypertensive action of these compounds.