RESUMEN
Before dissolving oxygen sensible drugs, water for injection is boiled and flowed through with nitrogen gas in order to reduce the amount of dissolved oxygen. The aim was to optimize the amount of oxygen of water for injection in manufacturing vessel for production. A 2(2)-1 type fractional factorial design was selected to study the parameters which can influence the amount of oxygen in water for injection. The following parametes were studied: gas pressure of nitrogen (X1), flowing time of nitrogen gas (X2), boiling time of water (X3) and amount of water (X4). Performing the factorial studies the coefficients were calculated and controlled by mathematical-statistical methods. Knowing the coefficients the factorial area was left the optimum was found by Box--Wilson method.