What is meant by the First-Pass Effect of drugs?

Question

Dylan Andrews · Accepted Answer

After oral administration, many drugs (morphine, pentazocine) are absorbed intact from the small intestine and trasported first via the portal system to the liver, where they undergo extensive metabolism. This process is called the first-pass effect.

Although every tissue has some ability to metabolize drugs, the liver is the principal organ of drug metabolism. Some other tissues show considerable activity, for example the gastrointestinal tract, the lungs, the skin, the kidneys and the brain.

first-pass effect is a process in which a drug administered by mouth is absorbed from the gastrointestinal tract and transported via the portal vein to the liver, where it is metabolized. As a result, in cases of some drugs, only a small proportion of the active drug reaches the systemic circulation and its intended target tissue.

In cases of those drugs, which has high first-pass effect, oral administration is avoided, to get the desired effect. For example lidocaine is administered locally or IV and morphine is administered intravenously (IV). First-pass effect can be also be bypassed by administering the drug via sublingual or buccal routes.

HIX Tutor · Answer

undefined The First-Pass Effect refers to how some drugs are processed in your body after you take them by mouth (like swallowing a pill). Here's how it works in simple steps:

1. When you take a drug by mouth, it goes into your stomach and then into your small intestine.
2. The drug is absorbed from your small intestine into your bloodstream.
3. The drug then travels to your liver, which is an organ in your body that helps process things.
4. In the liver, some drugs may be broken down or modified before they are sent into the rest of your body.
5. After being processed in the liver, the drug finally enters your bloodstream again and can start to have an effect on your body.

So, the First-Pass Effect means that some drugs can be broken down or changed by your liver before they even get a chance to fully work in your body. It can affect how much of the drug actually reaches your bloodstream and therefore how effective the drug is.

Autumn Anderson · Answer

undefined The first-pass effect of drugs refers to the phenomenon where a drug is metabolized by the liver to a significant extent before it enters the systemic circulation. This can result in a reduced bioavailability of the drug, meaning that a smaller amount of the drug reaches the bloodstream compared to the dose administered.