What do LD50 and ED50 represent, and how is the therapeutic index calculated?

• A. LD50 is dose producing 50% of the therapeutic effect; ED50 is lethal dose to 50% of organisms; TI = ED50/LD50.
• B. LD50 is the dose lethal to 50% of organisms; ED50 is the dose producing the minimum effect; TI = ED50/LD50.
• C. LD50 is the dose lethal to 50% of organisms; ED50 is the dose producing the desired effect in 50%; TI = LD50/ED50.
• D. LD50 is the dose that causes adverse effects in 50% of individuals; ED50 cures 50% of cases; TI = LD50/ED50.

Answer: (C)