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Hepatic First-Pass

Meaning

Hepatic first-pass metabolism, often termed the first-pass effect, is a critical pharmacokinetic phenomenon where the concentration of a drug, especially one taken orally, is significantly reduced before it reaches the systemic circulation and its intended site of action. This reduction occurs because the drug is absorbed from the gastrointestinal tract and immediately transported via the portal vein directly to the liver, the body’s primary metabolic organ. The extent of this effect dictates the required oral dosage and the bioavailability of many hormone therapies, such as oral estrogen and testosterone formulations. Understanding the first-pass effect is essential for clinical dosing and selecting the appropriate route of administration.