The route of administration with the first clearance elimination effect is as follows

The main route of administration that can cause first-pass elimination is (oral).

First-pass elimination: First-pass elimination refers to the phenomenon that drugs are partially eliminated by the liver after oral or rectal administration. This is because after oral administration, drugs are absorbed from the gastrointestinal tract and then enter the portal vein system, and then flow through the liver for metabolism, and some drugs will be metabolized in the liver, thus reducing the effective concentration of drugs in the body.

Main routes of administration: First-pass elimination mainly occurs in oral and rectal routes of administration. Specifically:

1. Oral: After the drug enters the gastrointestinal tract, it will be absorbed into the portal vein system and then enter the liver. In the liver, drugs may be metabolized into active metabolites or inactive metabolites, and some drugs will be eliminated in the process, thus reducing their effective concentration in the circulatory system.

2. Rectal administration: Similar to oral administration, drugs will enter the liver after entering the portal vein system through rectal administration. Although rectal administration avoids the influence of the stomach, it still goes through the first-pass metabolism of the liver, which may lead to drug degradation in the body.

However, not all drugs will be affected by the first-pass elimination, because the metabolism and elimination pathway of drugs are affected by many factors such as drug characteristics and liver enzyme activity. Some drugs are metabolized in the liver and become active metabolites, which may affect the curative effect of drugs and may also cause drug toxicity.

In a word, first-pass elimination is an important concept of drug metabolism and elimination, which mainly occurs in oral and rectal administration routes. Through the action of liver, some drugs are metabolized and eliminated in the body. Understanding the first-pass elimination route of drugs is helpful to rational drug use and achieve better therapeutic effect.