Serum ionized calcium--a predictor of therapeutic response to slow calcium channel blockade in essential hypertension

In 20 patients with mild to moderate essential hypertension, serum ionized calcium was determined before and after four weeks of treatment with 240 mg verapamil sustained release bid. Pretreatment systolic blood pressure was inversely correlated to serum ionized calcium (r = — 0.44, p = 0.05). Mean blood pressure was significantly (p < 0.001) reduced (from 161/100 to 145/88 mm Hg), but mean serum ionized calcium did not change during treatment (from 1.23 to 1.24 mmol/L). A significant inverse correlation (r = -0.56, p = 0.01) was found between pretreatment serum ionized calcium and reduction in systolic blood pressure during verapamil treatment. Thus serum ionized calcium in untreated essential hypertensive patients may predict the blood pressure response to the slow calcium channel blocker verapamil.