What is the Origin of Intramuscular Hormone Injections?

The technique of intramuscular injection has been a standard medical practice for drug delivery since the early 20th century, favored for its reliable absorption characteristics compared to subcutaneous or oral routes. Its application to hormonal therapy began in earnest with the mass synthesis of sex steroids, offering a practical means of long-acting hormone delivery.

What is the Mechanism of Intramuscular Hormone Injections?

Once injected into the highly vascularized muscle tissue, the oil-based hormone ester forms a localized depot. Enzymes in the muscle and bloodstream slowly hydrolyze the ester bond, cleaving the fatty acid chain from the active hormone molecule. This gradual hydrolysis controls the rate at which the free, biologically active hormone enters the circulation, resulting in the desired prolonged pharmacokinetic profile.

Intramuscular Hormone Injections ∞ Area

Intramuscular Hormone Injections

Meaning

Intramuscular Hormone Injections are a method of administering specific hormones, typically oil-based steroid esters like testosterone cypionate or enanthate, directly into a deep muscle mass, such as the gluteal or deltoid muscle. This route is chosen for its ability to create a slow, sustained release of the hormone into the bloodstream, minimizing the need for frequent dosing and providing relatively stable serum concentrations over several days or weeks. This method is a cornerstone of many hormone replacement protocols.