Question

The therapeutic index is defined as _______

• A. \(LD_{50}/ED_{50}\)
• B. \(ED_{50}/LD_{50}\)
• C. \(Dose/Time\)
• D. \(Clearance/Volume\)

Hint:

Therapeutic index \(= LD_{50}/ED_{50}\). Higher therapeutic index means greater safety margin.

Answer 1

The Correct Option is A

Concept:
Therapeutic index is a measure of drug safety. It compares the toxic dose with the effective dose.

Step 1: \(ED_{50}\) means median effective dose. It is the dose effective in \(50%\) of the population.

Step 2: \(LD_{50}\) means median lethal dose. It is the dose lethal in \(50%\) of test animals.

Step 3: Therapeutic index is calculated as: \[ TI = \frac{LD_{50}}{ED_{50}} \]

Step 4: A higher therapeutic index means a safer drug.

Step 5: Therefore, therapeutic index is \(LD_{50}/ED_{50}\). \[ \boxed{\frac{LD_{50}}{ED_{50}}} \]