RESUMO
To study the influence of sodium on the antihypertensive effect of a calcium entry blocker (CEB), 11 hypertensives with chronic renal failure (CRF), whose blood pressure was uncontrolled by hemodialysis, randomly received nifedipine (10 mg p.o.) or the corresponding placebo before and after dialysis, reversing the sequence the next week. Dialysis induced a similar sodium loss during the two experimental periods (-339.0 +/- 26.7 vs. -348.8 +/- 26.4 mEq) and did not significantly change blood pressure. When compared with placebo, nifedipine significantly (p less than 0.05 or less) reduced mean blood pressure and increased heart rate both before and after dialysis, with a peak effect at the first hour. However, both absolute and percentage decrements of mean blood pressure induced by nifedipine before dialysis were significantly (p less than 0.05 or less) greater than those after dialysis. These data indicate that the acute hypotensive effect of nifedipine is greater during sodium repletion than during sodium depletion, a finding that suggests a positive interaction between sodium and the antihypertensive action of CEBs.
