Question.......................... - psychmledr

[ArchivalUser]

A drug has an ED50 of 5 mg/kg adult body weight and a TD50 of 250 mg/kg body weight. The therapeutic index of the drug is:

A. Indeterminate
B. 0.02
C. 50
D. Too low to make the drug useful
E. Too high to make the drug safe

[ArchivalUser]

C. Thank you.

[ArchivalUser]

C is right. What does a TI of 50 mean?

[ArchivalUser]

Well, the higher the ratio the better. It would mean that the patient needs to take higher doses of the drug to reach toxic levels. Not sure where 50 would fall, though.

[ArchivalUser]

Yes, that is correct.

Know any drugs that have a low TI?

[ArchivalUser]

Digoxin, lithium....

[ArchivalUser]

Yes, and warfarin, theophylline, .......

Thank you, fmg8

[ArchivalUser]

Thank you, Psychmledr.

[ArchivalUser]

Thanks for the question! I have a doubt..
I learnt that

TI = LD 50 / ED 50

LD 50 = lethal dose in 50% population
ED 50 = effective dose for 50% population

What is TD 50?

[ArchivalUser]

Hi escada04

TD50 = Toxic dose in 50% of the population.

Both terms are similarly used and applied in this equation of TI

TI = TD50/ED50 OR LD50/ED50

According to Kaplan, LD 50 is "mainly used in animal models."

I say know them both. I've seen both terms used in pharma problems like this one.