SALT AND BLOOD-PRESSURE RESPONSES TO CALCIUM ANTAGONISM IN HYPERTENSIVE PATIENTS

Since salt intake may affect blood pressure response to antihypertensi ve drugs, an individual's salt-sensitivity status may be an important consideration in the selection of a medication. The purpose of this si ngle-blind study was to assess the impact of salt sensitivity on the a ntihypertensive effects of isradipine. A total of 21 evaluable hyperte nsive patients (10 white, 11 black) 35 to 73 years of age (mean 55.9 y ears) were randomized to a low-salt diet (mean 24-hour urine sodium 10 0+/-14 mmol) or a high-salt diet (mean 24-hour urine sodium 210+/-22 m mol) for 7 weeks, followed by crossover to the other diet after a 2-we ek washout period. On each diet regimen, patients received placebo for 2 weeks, followed by optimal titration of isradipine (2.5 to 10 mg BI D) for blood pressure control during the last 5 weeks. On the high-sal t diet, salt-sensitive hypertensives (mean arterial blood pressure inc rease greater than or equal to 5 mm Hg, n=5) exhibited a systolic/dias tolic blood pressure change of -18.7/-19.6 mm Hg from 157.2/102.9 mm H g after 5 weeks of isradipine treatment: whereas on a low-salt diet, b lood pressure change was -6.9/-12.0 mm Hg from 148.7/97.3 mm Hg. Non-s alt-sensitive patients (n=16) exhibited a systolic/diastolic blood pre ssure change of -12.6/-7.6 mm Hg from 155.3/98.6 mm Hg on the high-sal t diet and -19.2/-10.9 mm Hg from 161.6/102.6 mm Hg on the low-salt di et after treatment with isradipine. The absolute blood pressure attain ed in both salt-sensitive and non-salt-sensitive patients was almost i dentical with isradipine therapy despite variation in dietary salt, al though slightly higher doses of isradipine were required in the salt-s ensitive group. Consequently: isradipine, and perhaps calcium antagoni sts in general, manifests a more robust blood pressure-lowering effect in the setting of high sodium intake. This effect does, however, appe ar to be largely confined to individuals who are salt sensitive.