[Potentiation of the antitumor action of cyclophosphamide with a change in the cell population makeup and an increase in cellular permeability].

Cells of Ehrlich ascites tumor survived after cyclophosphamide injection showed no multiplication during 48 hours. As a result, vinblastine injection simultaneously with cyclophosphamide or following 24 hours produced no additional death of cells. The administration of cyclophosphamide 6 hours after vinblastine resulted in the death of cells 30 times as much as in the injection of both substances simultaneously. Synergism was due to the disappearance of cells in phase G from the population, which are resistant to cyclophosphamide. Tween 80 enhanced an antitumor effect of cyclophosphamide without increasing the toxicity.