What is the Origin of Intramuscular Progesterone?

Progesterone is a naturally occurring progestogen, essential for regulating the menstrual cycle and maintaining pregnancy. The intramuscular route was developed early in the history of hormone therapy to overcome the poor oral bioavailability and rapid hepatic metabolism that plague micronized progesterone capsules. The method's origin is rooted in the clinical need for reliable, high-dose delivery.

What is the Mechanism of Intramuscular Progesterone?

Administering progesterone intramuscularly allows the hormone to bypass the digestive tract and the initial "first-pass" metabolism by the liver, resulting in predictable, sustained therapeutic serum levels. The hormone then acts on its nuclear receptors, transforming the uterine lining from a proliferative state to a secretory state, preparing the endometrium for embryo implantation and maintenance of early pregnancy. This systemic delivery contrasts with vaginal administration, which favors local uterine concentration.

Intramuscular Progesterone

Meaning

Intramuscular progesterone refers to the pharmaceutical administration of the steroid hormone progesterone via injection directly into a muscle, typically dissolved in an oil solution. This route is used to achieve high, stable, and prolonged systemic concentrations of the hormone in the bloodstream. It is a highly effective method for providing luteal phase support in fertility treatments.