Delivery route choices for progesterone: Intramuscular (I.M.) Injections

Most common administration in clinics

Guarantees adequate and verifiable plasma levels of active component.  Effective in infertility.

PROGESTERONE half-life significantly longer than when injected into arm.   Due to higher concentration of adipose cells, which store then release PROGESTERONE when plasma levels decrease;

Injections cause pain at injection site

They are also inconvenient and invasive, but do get the hormone directly into the blood stream and are tolerated by those women highly motivated to reduce threat of abortion, prevent pre-term labor and for assisted reproduction (especially those with PCOS who are resistant to clomiphene citrate, which is used to stimulate hormones promoting ovulation); for those not willing to undergo the pain, this is not an effective method for long-term treatments.