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Figure 2 Mean standing heart rate in tadalafil (20 mg)- and placebo-treated subjects. Sublingual nitroglycerin (0.4 mg) is indicated by dashed vertical line. The 4- to 96-h time intervals represent time of nitroglycerin administration after last dose of tadalafil or placebo. Standard deviation for time points ranged from 10 to 16 beats/min (bpm).