Leukopenia Following Administration of Nicotinic Acid

1. Intravenous nicotinic acid produces an immediate and marked neutropenia, which disappears within 15 minutes. The lymphocytes frequently show a slight reduction; but the red cell count, hematocrit and platelet count reveal no significant variation. 2. This response was similar in splenectomized and nonsplenectomized subjects. 3. In 2 patients with leukemia the white cell count was reduced in 5 minutes by nicotinic acid from 177,800 to 146,400 and 73,300 to 33,600. 4. The mechanism of the granulocytopenia after nicotinic acid is discussed in relation to its vasodilatation action and the distribution of leukocytes in the vascular system. This concept is outlined in table 5.