The First Pass Effect in Pharmacology

The First Pass Effect in Pharmacology
Coming up next: Mnemonics for Pharmacological Terminology

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
 Replay
Your next lesson will play in 10 seconds
  • 0:00 The First Pass Effect
  • 1:11 The Stomach
  • 1:41 The Intestines
  • 2:52 The Liver
  • 3:41 Lesson Summary
Save Save Save

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Log in or Sign up

Timeline
Autoplay
Autoplay
Speed

Recommended Lessons and Courses for You

Lesson Transcript
Instructor: Artem Cheprasov
Did you know that when you take a pill, only a fraction of that pill actually makes it into general circulation? Do you know why this is so? It has something to do with the first pass effect.

The First Pass Effect

When you take a medication by mouth, it doesn't just magically get into your body and start doing its thing. It actually has to go through a whole host of organs and a big number of biochemicals in order to finally enter general circulation and actually exert its intended effect upon your body. In fact, the amount of a drug that is actually delivered to your general circulation is less than the total amount you initially took by mouth as a result of all of this. This concept is known as the first pass effect.

This is like someone hiking through the woods trying to get back to their car. They don't just magically teleport to the car. No! They have to go through various sections of the woods and avoid perils like wild animals that could rip off some clothing or even an arm! What's left of the person after they get back to the car is due to their own kind of first pass effect.

In other words, some of the drug is lost as it passes through the gastrointestinal system and the liver prior to reaching general circulation. That's what the first pass effect is all about. Let's explore why this is the case.

See if you can spot the organs we discuss in this lesson that are involved in the first pass effect.
Digestive system

The Stomach

Imagine taking a pill. Once you swallow that pill, it plops into the stomach. The stomach is a vat of acid. It has some very low pH (so it's acidic). We all know seriously acidic stuff can destroy even metal. Well, stomach acid can destroy some parts of a drug. As if that wasn't enough for the poor drug particles, next these guys are pumped out into the intestine from the stomach. It's not much safer here for what's left of the pill.

The Intestines

The gastrointestinal tract can contribute significantly to the first pass effect. This happens in many ways.

To unlock this lesson you must be a Study.com Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use Study.com

Become a Study.com member and start learning now.
Become a Member  Back
What teachers are saying about Study.com
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? Study.com has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account
Support