Standard versus Low-Dose Transdermal Nitroglycerin: Differential Effects on the Development of Tolerance and Abnormalities of Endothelial Function

We compared standard (0.6 mg/h) versus low-dose (0.05 mg/h) transdermal nitroglycerin (TGTN) on acute hemodynamic parameters, the development of tolerance, and endothelial function. Study 1 randomized six healthy volunteers to receive 0.6 mg/h or 0.05 mg/h TGTN in a crossover design study (6-day washout period) with measurements of heart rate, blood pressure, radial artery waveforms, and aortic augmentation index taken at baseline and 1, 2, and 3 hours after initial TGTN application. Study 2 enrolled 24 healthy volunteers to receive 400 μg of sublingual nitroglycerin spray followed by 400 μg of inhaled salbutamol 90 minutes later. Measurements of heart rate, blood pressure, radial artery waveforms as well as aortic augmentation index were taken at baseline and at 5, 10, and 20 minutes after each treatment. They were randomized to either 0.6 mg/h or 0.05 mg/h of TGTN, and the same measurements were repeated after 6 days. In Study 1, there was no significant difference in the response to both doses (analysis of variance, P < 0.05). In Study 2, the decrease in aortic augmentation index in response to sublingual nitroglycerin and salbutamol was attenuated after sustained therapy with 0.6 mg/h of TGTN (versus 0.05 mg/h, P < 0.05). This investigation documents that 0.05 mg/h TGTN has identical acute hemodynamic effects compared with 0.6-mg/h dose without causing tolerance or endothelial dysfunction.