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}\. \[ \boxed{\frac{LD_{50}}{ED_{50}}} \]