The paper presents the construction of an automatic applicator of active substance that removes causes of the disturbances in the fluid flow in a system that is under the control. In a particular case, it can be applied to the removal of disturbances in the blood flow in vessels caused by a thrombus formation (e.g. post-operative or due to dialysis treatment). The presented applicator automatically releases the active substance into the system while detecting in real time the abnormal fluid flow. It allows mixing the active substance (e.g. anticoagulant drug) with the controlled medium outside the substance container (e.g. serum) while offering the possibility of the repeated usage.