Nitroglycerin and isosorbide dinitrate in pulmonary hypertension of chronic obstructive pulmonary disease

The effects of sublingual isosorbide dinitrate (ISDN; 10 mg) or nitroglycerin (NTG; 1 mg) on pulmonary hemodynamics, gas exchange and pulmonary function were studied during right heart catheterization in two series of 27 patients with COPD. An immediate significant decrease of pulmonary arterial pressure, cardiac output and work of the right ventricle was obtained with both drugs, but NTG only was able to reduce the pulmonary vascular resistance. Arterial oxygen tension did not decrease, but venous O2 tension did, with no change in blood lactate. NTG had also a slight bronchodilating effect. After chronic use, no improvement of pulmonary function or gas exchange was observed but NTG lowered pulmonary vascular resistances significantly. The effects observed during the acute study were reproduced after six weeks with the same doses of both drugs. NTG appears effective in reducing pulmonary arterial hypertension mainly by vasodilation while the ISDN effect seems due only to the decreased cardiac output.