Relation of time course of plasma nitroglycerin levels to echocardiographic, arterial pressure and heart rate changes after sublingual administration of nitroglycerin.

Despite the widespread use of nitroglycerin, a relation between plasma nitroglycerin concentrations and the associated cardiovascular effects has not been well established. It was hypothesized that nitroglycerin levels may help predict the hemodynamic responses. With use of a recently developed nitroglycerin assay technique, the relation between the time course of plasma nitroglycerin levels and echocardiographic changes after sublingual administration of 0.6 mg of the drug was evaluated in 12 normal volunteers. Mean plasma nitroglycerin levels were maximal at 2 (1.1 +/- 0.3 ng/ml) and 5 (1.4 +/- 0.6 ng/ml) minutes, when the changes in mean heart rate (+17 +/- 7 and +12 +/- 3 min-1) and decreases in echocardiographic left ventricular diastolic (-4.2 +/- 0.8 mm at 5 minutes) and systolic (-3.1 +/- 0.6 mm at 5 minutes) dimensions were also maximal. Parallel changes were noted in left atrial dimension, ventricular velocity of circumferential fiber shortening and systolic blood pressure, but not in diastolic blood pressure. These findings demonstrate the existence of a close relation between plasma nitroglycerin levels and variables that reflect the known responses to this drug.