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Do you know what happens to drugs after they pass through the liver? Explore the mystery of the first-pass effect!
How a drug is absorbed, distributed, metabolized and excreted after entering the human body is called pharmacokinetics of the drug. Among them, the first-pass effect is an important concept, which describes the metabolic process of drugs after passing through the liver. This information not only affects the efficacy of drugs, but also affects patient outcomes.
The metabolic effects of a drug as it passes through the liver can lead to a significant decrease in the concentration of the drug that actually enters the systemic circulation. This is called the first-pass effect.
The mechanism of first pass effect
When a drug enters the body through oral or other non-intravenous routes, the first step is to enter the intestine, where it is absorbed into the portal venous system and eventually reaches the liver. In the liver, drugs may be converted into other active or inactive forms after being metabolized by liver enzymes, which often causes some drugs to lose their efficacy early.
Different drug ingredients have different metabolic pathways. Some drugs may undergo extensive metabolism in the liver, while others may enter the systemic circulation entirely through filtration by the liver. This makes the bioavailability of some drugs relatively low when taken orally, and sometimes even affects the patient's experience of efficacy.
Research shows that compared with intravenous administration, the bioavailability of drugs through oral administration is usually less than 100%; this is because some drugs have a first-pass effect when passing through the liver.
Factors affecting the first pass effect
The first-pass effect is affected by many factors, including the physical and chemical properties of the drug, dosage form and administration method. Some oral medications are designed as extended-release or controlled-release dosage forms, which help reduce the effects of first-pass metabolism. Additionally, taking a drug with food can alter the rate of drug absorption, which can affect its bioavailability.
The chemical structure of a drug is also an important factor affecting bioavailability. Drugs with high fat solubility usually easily penetrate cell membranes and enter the systemic circulation, while drugs with low fat solubility may be rapidly metabolized in the liver, resulting in a decrease in concentration and affecting efficacy.
In addition, physiological conditions such as liver health, intestinal function, and age will affect how and how quickly drugs are metabolized in the body.
How to deal with the first-pass effect?
Medical professionals often take the first-pass effect into consideration when prescribing, especially when a drug has relatively low bioavailability. They may adjust the dose or choose an alternative route of administration to ensure patients receive adequate concentrations of the drug to treat their disease. Sublingual or rectal administration is sometimes chosen to bypass the first-pass effect of the liver and enter the systemic circulation directly.
During the development process of many drugs, compounds that can penetrate biological membranes and reduce the first-pass effect are deliberately designed to better improve the bioavailability of oral drugs. The development of this type of new drugs not only improves treatment effects, but also helps reduce patients' medication burden.
Conclusion
Generally speaking, the first-pass effect of drugs is an important factor affecting drug efficacy. Understanding its mechanism and influencing factors can help medical personnel better manage drug regimens. This not only involves the characteristics of the drug itself, but is also closely related to the patient's physiological condition. In future drug research and development, how to improve the bioavailability of drugs and challenge the first-pass effect will be one of the key issues. Have you ever wondered how these tiny chemical changes alter the effectiveness of a drug?
