Which statement about the first-pass effect is true?

• A. It increases the amount of drug reaching systemic circulation
• B. It decreases the amount of drug reaching systemic circulation
• C. It only affects IV drugs
• D. It has no clinical significance

Answer: (B)

The first-pass effect is about how much of a drug is lost to metabolism before it ever reaches systemic circulation. When a drug is taken orally, it is absorbed from the gut and first travels through the hepatic portal vein to the liver (and also the gut wall) where many drugs are metabolized by enzymes. This metabolism can significantly reduce the amount that enters the bloodstream unchanged, lowering its bioavailability. Because of this, the administered oral dose is often higher than the amount that actually reaches systemic circulation.

This is why the statement that the first-pass effect decreases the amount of drug reaching systemic circulation is true. It helps explain why some drugs have high oral doses or are given via other routes (such as sublingual, transdermal, or IV) to bypass or minimize this metabolism. The first-pass effect is clinically significant for many medications and isn’t limited to IV drugs; it does not increase systemic exposure, and it can be bypassed by alternatives that avoid the hepatic first pass.