Effect of molsidomine on the lung diffusing capacity of normal men

Molsidomine (M) is a new antianginal drug which induces a peripheral venous pooling and decreases pulmonary artery and pulmonary venous pressures. The purpose of our study is to assess whether M influences the filling of the pulmonary capillary bed as estimated by the single-breath lung diffusing capacity (DLCO). DLCO was measured before and 10, 20, 30, 40, 50 and 60 minutes after sublingual administration of 2 mg molsidomine in six healthy men examined in sitting and supine positions. The blood flow distribution was estimated by means of radioactive xenon, in sitting position only, before and 30 minutes after M intake. M. induces a significant fall in DLCO from the 20th to the 60th minute which indicates an emptying of the pulmonary capillary bed. Concomitantly, blood flow is redistributed from the apices to the lung bases. We explain the decrease in DLCO by two mutually non-exclusive mechanisms: an outflow of the blood from the thorax to the periphery and a change in the lung-perfusion distribution. From a practical point of view, two conclusions may be reached. First, in coronary patients a decrease in DLCO and DLCO/VA may be due to the intake of vasodilating agents such as molsidomine and not to emphysema or lung fibrosis. Secondly, the measurement of DLCO is a useful tool to assess the action of a drug on the pulmonary circulation.