Isosorbide dinitrate. Effect on the vasodilator response to nitroglycerin
R. Zelis and D. T. Mason
To evaluate whether there is cross-tolerance to the circulatory effects of
isosorbide dinitrate and nitroglycerin, six subjects were given 120 mg/day
of sustained-action isosorbide dinitrate in three divided doses for six to
eight weeks. Prior to and during the last week of long-term isosorbide
dinitrate administration, the effects of sublingually given nitroglycerin
(0.9 mg) on plethysmographically measured calf blood flow and venous volume
at 30 mm Hg (VV[30]) were measured on three occasions and averaged.
Although the arteriolar dilation produced by nitroglycerin was unaltered by
isosorbide dinitrate, the venodilation was significantly attenuated. The
VV[30] increased from 3.00 to 3.28 ml/100 ml (P less than .02) with
nitroglycerin prior to isosorbide dinitrate administration, but failed to
increase with nitroglycerin during the long-term administration of
isosorbide dinitrate (2.95 to 2.95 ml/100 ml, P greater than .5).
