Structural Biochemistry/Intramuscular


An intramuscular (IM) injection is a drug administration route in which a drug is injected into a muscle. In terms of absorption, the injection methods that delivers the drug quickest to slowest is intravenous, intramuscular then subcutaneous. It is favored due to its fast-acting as well as long-lasting capabilities. These injections are inserted into the deep muscle tissue where the deposition of medication is absorbed gradually into the bloodstream.


The three main sites of intramuscular injection is in the deltoid muscle of the arm, buttocks and the thighs. Absorption is quickest when injecting into the arm and slowest in the buttocks.


When injecting into the muscle, there is less chance of irritation due to greater blood supply and faster absorption. Also, when wanting to inject larger amounts of drugs, it is best to inject into the muscular region instead of injecting subcutaneously.


Needle should not be smaller than an inch nor exceed one and a half inches in length. The maximum volume of medication recommended should be five milliliters at one site per adult.


  1. Hart, Carl. Drugs, Society, and Human Behavior. 12th. McGraw-Hill Humanities, 2008. Print.

"ADMINISTER AN INTRAMUSCULAR INJECTION."Administer Intramuscular, Subcutaneous, and Intradermal Injections. Brookside Associates, n.d. Web.