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Uterine First-Pass Effect

Meaning

A physiological phenomenon observed with certain routes of hormone administration, specifically referring to the high concentration of a drug that is delivered directly to the uterus before it enters the systemic circulation and undergoes significant hepatic metabolism. This effect is most notable with vaginally or locally administered progesterone, which achieves high endometrial concentrations while minimizing systemic exposure and associated side effects. It is a key pharmacokinetic consideration in targeted hormone therapy.