The main reason for this is that when using intravenous infusion, the drug can flow back through the blood to the heart and through the heart through the arteries to the whole body and finally to the target point where it needs to act. There are other reasons why we use veins for infusion, such as the arteries have higher blood pressure, which makes it difficult to get the fluid through the normal pressure during the infusion on the one hand, and the needle holes are prone to bleeding during and after the infusion on the other hand. In addition, the artery is located deeper, invisible, and difficult to enter because of its thick wall and thin lumen, as well as the need to compress to stop bleeding after needle extraction, but it is very difficult to compress because the blood pressure of the artery is too high. On the other hand, since in some locations there may be only one main blood supply artery, compression may lead to bleeding, and for these reasons, the needle is usually given in a vein.