Potency, Efficacy and Therapeutic Index

What are Quantal Studies? What is it used for?

Studies measuring Yes/No responses from patients to determine medication efficacy

What is ED50? What is its significance

• The dose required to produce a response in 50% of the total patient population

What is the therapeutic index? How do we determine it when given a graph?

• helps determine how many times in excess can a patient take a medication before exhibiting toxic symptoms

  • Look at where ED50 and TD50 is on the graph, divide TD50 by ED50

What is TD50?

Amount of drug it takes to cause 50% of total patients to exhibit toxicology symptoms 

What does it mean when the therapeutic index is high? Low?

High: The Safer the drug is to consume (large buffer zone before the therapeutic drug concentration gets toxic.

Low: The more dangerous etc…

What are Dose-Response Curves? What do Phase 1, 2 and 3 mean within it?

• used to determine graded responses and magnitude of biologucal response of drug\

• Phase 1: Few cells effected by dose

• Phase 2: Linear relationship between patient and dose

• Phase 3: Highest plateau reached ; increasing dose from now on will cause adverse effects

Define potency, and what is ED50 considered in this case?

• the affinity between drug and its receptor

  • The dose of drug that ilicits 50% of the maximum biological effect of drug

What is efficacy?

Ability of drug to exert 100% of its max biological response (basically ED50 but its now 100%: probably called ED100)

In terms of dissociation and association, what do we look for in a drug?

• Fast association, slow dissociation

Symbol of dissociation constant, and its formula

Symbol: Kd

Why is Kd important and what does it tell us (2)

• High Kd: low drug to receptor affinity

• Low Kd: high drug to receptor affinity