Intradermal injection is generally used during vaccination or allergy sensitivity tests. It is performed using a short needle around 1.5 centimeters long. Subcutaneous injection reaches the tissue located under the skin, superficial to the muscles. It is suited to products which should be absorbed more slowly such as analgesics and some antibiotics.
There is then the intramuscular, or IM injection. It is an alternative and rapid administration route. The muscles, with a profuse blood supply, absorb the active principle more quickly, allowing it to act just as quickly. The intravenous route bypasses the absorption barrier. The product is injected directly into the circulatory system and its action is practically instantaneous. Finally, we speak of a bolus when the drug must be injected in a single solitary dose. Rapid and speedy, it is administered by continuous intravenous perfusion, which acts as a drug vehicle.