## **Core Concept**
Gentamicin is an aminoglycoside antibiotic that is primarily used to treat severe bacterial infections. Aminoglycosides are known for their poor absorption from the gastrointestinal tract. This characteristic influences their route of administration.

## **Why the Correct Answer is Right**
Gentamicin is not given orally because it is poorly absorbed from the gastrointestinal tract. This poor absorption is due to its polar, charged nature, which hinders its ability to cross cell membranes and be absorbed into the bloodstream. As a result, when administered orally, gentamicin remains in the gut lumen, where it can be effective against certain infections, but systemic levels are not achieved.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is not provided, but typically, incorrect options might suggest reasons like gentamicin being metabolized by the liver or causing gastrointestinal upset. However, gentamicin's primary issue with oral administration is its poor absorption.
- **Option B:** Similarly, this option is not provided, but it might suggest gentamicin is inactivated by stomach acid. While pH can affect drug stability and activity, gentamicin's poor absorption is the main reason it's not given orally.
- **Option C:** Without the specific text, we can't directly address why this option is incorrect, but any option suggesting gentamicin is ineffective orally or causes a specific side effect when given orally would not capture the primary reason related to its pharmacokinetics.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that aminoglycosides, like gentamicin, are not absorbed orally, which is why they can be used in bowel preparations for decontamination without systemic absorption. However, for systemic infections, they must be administered intravenously or intramuscularly.

## **Correct Answer:** B. Poor absorption from GIT.