Circulatory effects of sublingual and oral sustained-release nitroglycerin in healthy young men.

The effects on heart rate and blood pressure during standing, and on plethysmographic arterial pulsation in the calf, of nitroglycerin 0.5 mg sublingually, 6.5 mg orally and a placebo tablet were studied for up to 8 h. Sublingual nitroglycerin increased heart rate and arterial pulsation; the peak height and duration of these effects occurred at slightly different times. Oral nitroglycerin had no effect on heart rate but did increase pulsations as compared to placebo. In the orthostatic test, heart rate and pulse amplitude were affected by both forms of administration. Comparing the areas-under-curve for these variables for the two forms suggested that, in comparison with sublingual nitroglycerin, about 1/3 of the oral nitroglycerin was biologically effective over 8 h. Pulse plethysmography appeared to be the most sensitive method for "bioassay" of nitroglycerin.