Intramuscular (or IM) injection is the injection of a substance directly into a muscle. In medicine, it is one of several alternative methods for the administration of medications (see route of administration). It is used for particular forms of medication that are administered in small amounts. Depending on the chemical properties of the drug, the medication may either be absorbed fairly quickly or more gradually. Intramuscular injections are often given in the deltoid, vastus lateralis, ventrogluteal and dorsogluteal muscles. Less