Question

3. Be explicit in your discussion of ED_{50 ,} LD_50, TD₅₀: what each of these are and explain in detail why it matters. Please give 2 examples of each.

Answer 1

ANSWERS:-  

# ED50 or the" median effective dose" is the dose that produces a quantal effect in 50% of the population that takes a particular medicine.

*It is the effective dose for the 50% of the population.

*Example :- Administering 1000mg of acetaminophen (ED50) orally will result in a plasma concentration of 15ug/ml, which produces effective pain relief in 50% of adult patients.

# TD50 or median toxic dose is the dose required to produce a defined toxic effect in 50% of subjects.

# LD50 or median lethal dose is the dose required to kill 50% of subjects.

** The Median toxic dose (TD50) of a drug or toxin is the dose at which toxicity occurs in 50% of cases.The type of toxicity should be specified for this value to have meaning for practical purposes.

** The median toxic dose (TD50) encompasses the category of tixicity that is greater than ED50 but less than LD50.

Therapeutic index(TI) is used to compare the therapeutically effective(TD50) dose to the toxic dose(TD50) of a pharmaceutical agent. The TI is a statement of relative safety of a drug. It is the ratio of the dose that produces toxicity to the dose needed to produce a desired therapeutic response. The common method used to derive TI is to use the 50% dose response points including therapeutic dose(TD50 ) and toxic dose(TD50).

TI=TD50 /ED50

* example:- if the TD50 is 200 and the ED50 is 20mg, the TI is

TI= TD50/ED50=200/20=10.

*THE ED50, TD50 and LD50 of a drug is important to know inorder to prescribe the most effective dose and to prevent toxicity and death.

## For Digoxine, the therapeutic serum level is 0.8 to 2ng/ml and cause toxic effects when the serum level is more than 2ng/ml. So it is important for the physician to monitor and adjust the dose within the therapeutic level and not reaching toxic level.