Drug delivery is usually considered using a stirred tank model, which does not include all the mass transfer resistances. A distributed system called Krogh cylinder has been used here. The complex capillary network is broken down into cylindrical cells, each containing a capillary and appropriate amount of extravascular tissue. The flow has two-dimensional velocities, which are in the axial and the radial directions. Most of the drug uptake happens through convection, which is slowed down in the presence of a reaction. Local equilibrium is assumed, which cuts down the computations and provides good results for the case of reactive solutes. The results of a distributed system have been obtained for the first time, and mechanics of how area-under-the-curve can be used to calculate the actual solute uptake is illustrated. The results emphasize the need for a higher rate of perfusion in the tumor because of the importance of convection.