Blood viscosity and oral anticoagulant therapy.

During administration of bishydroxycoumarin, hematocrit, viscosity of whole blood, and viscosity of plasma decreased in samples from nine healthy volunteers and 31 patients who had coronary heart disease. The relationships between viscosity of blood and intensity of anticoagulant therapy varied from patient to patient. Discontinuation of the drug was followed by return of viscosities to pretreatment levels in two to four days. The decrease of viscosity of blood by anticoagulant therapy may explain the relief of anginal pain in patients who have coronary heart disease.