August 1990

Calcium Channel Blockers as Second-Line Therapy in Thiazide-Resistant Hypertension

Arch Intern Med. 1990;150(8):1755-1758. doi:10.1001/archinte.1990.00040031755032

To the Editor.—  We would like to make three major comments on the work of Prisant et al1 as a second-line antihypertensive medication in thiazide-resistant hypertension, and showing that this combination therapy is as efficient and safe as a more classical combination of propranolol and thiazide.Thiazides and calcium channel blockers have different mechanisms of action, the thiazide controlling the sodium-retaining process of hypertension and the calcium antagonist acting primarily as a vasodilatory drug. A direct natriuretic effect has been demonstrated for different dihydropyridine calcium channel blockers. For isradipine this effect is present both acutely and chronically, lasting for at least 3 months.2 One might ask if the additive hypotensive effect of isradipine to hydrochlorothiazide is due only to the vasodilatory effect of the drug, or also to an additional natriuretic effect. In this respect, comparing the 24-hour sodium excretion of the two groups of patients might have been of interest.It has