EFFECT OF WETTING THE MOUTH ON AORTIC BLOOD-PRESSURE JUST BEFORE TAKING SUBLINGUAL NITRATES

The absorption of sublingual nitrate tablets is sometimes variable. We performed a randomized controlled trial to determine whether wetting the mouth improved the decrease in aortic systolic blood pressure (BP) from sublingual nitrate tablet or spray. The 100 patients undergoing routine diagnostic cardiac catheterization were allocated to control ( no nitrate), 0.3 mg sublingual nitrate tablet, 0.4 mg sublingual nitra te spray, water +0.3 mg sublingual nitrate tablet, or water + 0.4 mg s ublingual nitrate spray. Aortic systolic and diastolic BP were recorde d using a fluid-filled catheter and measured offline blind to the trea tment group. Compared with control subjects, there were significant de creases in aortic systolic BP with both nitrate preparations (tablet = -7.1 mm Hg, 95% confidence interval [CI] = -12.5 to -1.6 mm Hg; spray = -8.0 mm Hg, 95% CI = -13.4 to -2.5 mm Hg). On average, water signif icantly increased the fall in aortic systolic BP with nitrate tablets (-5.5 mm Hg, 95% CI = -10.9 to -0.1 mm Hg, p = 0.044) but did not sign ificantly enhance the effect of nitrate spray (-2.8 mm Hg, 95% CI = -8 .3 to 2.6 mm Hg). Water significantly increased the fall in aortic dia stolic BP with tablets only (-2.9 mm Hg, 95% CI = -5.5 to -0.2), and h ad no significant effect on heart rate. Water had a consistently large r influence on the hemodynamic effects of nitrate tablets than on the effects of nitrate spray. Patients with a dry mouth will have an incre ased effect from sublingual nitrate tablets if they wet their mouth be fore using sublingual nitrate tablets. Water does not appear to assist in the action of sublingual spray.