chapter 4 Pharmacodynamics Flashcards
What is the median effective dose
-the dose in the middle of the frequency distribution curve
-the dose that is required to produce a therapeutic effect in 50% of patients in a group
-Usually the ED50 is average or standard dose of a drug
What is pharmacodynamics
what the mechanisms of drug action are and how drug drug concentration affects the body’s response
what are the three main pharmacodynamic factors that affect interpatient variability
Dose response relationships
Therapeutic index
drug receptor interactions
what is therapeutic Index***
ratio of drugs LD50 to its ED50 measure of a drugs safety margin the higher the value the safer the medication
how would you calculate therapeutic index
(median lethal dose)/(median Effective dose)
what is margin of safety
another indicator of a drugs effectiveness and safety
How is margin of safety calculated
(amount of drug that is lethal to 1% of animals)/(amount of drug that produces a therapeutic effect in 99% of animals)
What is dose response relationship
describes how the action of drug changes with increasing dose
what are the three phases of the dose response curve
1: lowest dose
2: Most desirable range
3: plateau reached
if you were to increase a dose past phase 3 of the dose response curve what could happen
if you were to keep increasing the dose it will only increase the toxic effects and not the therapeutic effects
WHat medication do you need to be very aware of the dose response relationship***
antibiotics
what is potency of a drug***
Amount of drug needed to produce a specific effect
what is efficacy of a drug***
Greatest maximal response produced by a drug
which one is more important efficacy or potency in determining if a drug is more therapeutic**
efficacy
What is receptor theory
states that majority of drugs produce therapeutic effects by inhibiting or stimulating receptor sites
if a drug had a high intrinsic activity what would that mean
this would mean that the drug has the ability to bind to a receptor and produce a strong action
do most drugs work by creating anew action within the body or enhancing or inhibiting a physiological response**
most drugs enhance or inhibit a physiologic process
What is an agonist drug
a drug that activates a receptor and produces the same type of response as the endogenous substance
can an agonist drug produce a greater response than normal endogenous activity
yes
what is an antagonist drug
a drug that prevents the action of endogenous substances and has no intrinsic activity itself it only produces an effect by blocking receptors
would you use an agonist or antagonist drug to reverse an OD
antagonist since it would block receptors and stop the OD from happening
how does functional antagonism produce an effect
it has an effect not by competing for receptors but by changing pharmacokinetic factors for example if a functional antagonist speed up metabolism it would reduce the absorption of an agonist
what is a partial agonist medication
medication that produces a weaker response than an agonist
do partial agonists have a ceiling effect
yes
what is a synergistic paring of drugs
when two drugs are given together so they have an enhanced effect (1+1=3)
what is a potentiate pairing of drugs
a drug that has no effect is given to enhance the effect of a drug that does have an effect (1+0=2)
What is an additive pairing of drugs
when two drugs with similar pharmacological actions are given together to produced a greatly enhanced effect (1+1=3)
What is a very common additive pairing of drugs
Diuretic and beta blocker to lower BP
what is a controlled substance***
a substance that has the potential for abuse or addiction that is regulated by the government
what is a scheduled drug***
a scaling system of a drugs abuse or dependancy potential
What factor is a reflection on a drug’s ability to bind to a receptor potency or efficacy
potency
What is a potential outcome of a prescription drug that has a high margin of safety***
may be reclassified as over the counter
once phase 3 of the dose response curve is reached what would happen if you increase the dose of antibiotics***
could result in toxicity
Can drugs in the same class differ in potency and efficacy? ***
Yes
What does therapeutic effect mean ***
Desired outcome
What does bioavailability mean ***
the amount of free drug in the blood stream available to interact with cells
What does safety margin mean***
the amount between a therapeutic dose and a lethal dose of drug
What is a therapeutic dose ***
the quantity of drug required to obtain the desired effect with a safe outcome
