Pharmacodynamics: DOSE- RESPONSE RELATIONSHIPS Flashcards
Define POTENCY:
A measure of drug activity expressed in terms of amount of drug that produces an effect of given intensity. A drug is considered potent if a small dose produces large biological effect.
POTENCY is relatively UNIMPORTANT in clinical use of drugs.
True/False
True
With respect to POTENCY, Fentanyl is more potent than meperidine.
T/F
True . At low dose fentanyl is able to evoke the same intensity of response as meperidine will at high concentration.
Define EFFICACY:
The ability of a drug to produce effect.
Emax is the minimal effect that can be produced by a drug. T/F
False. It is the MAXIMAL effect that a drug can produce.
Efficacy is determined mainly by:
Properties of the drug
Receptor-Effector System
Efficacy is an important clinical measure.
T/F
True.
Potency is a much more important clinical measure than efficacy.
True/False
FALSE! Efficacy is a much more important clinical measure as potency is relatively UNIMPORTANTLY in clinical use of drugs.
______ help in estimating the safety of a drug.
Dose- Response Curve
Therapeutic Index is given as(it’s formula):
T.I= LD50/ED50
LD50: MEDIAN LETHAL DOSE OF DRUG IN ANIMALS(from slide)
ED50- is the conc. given to 50% of the population to produce clinical effect.
LD50- is the conc. given to 50% of the population to produce toxic/lethal effects.
Types of Antagonism:
Pharmacological
Physiological
Chemical
Chemical antagonism, it is caused by:
Combination of agonists with antagonists with resulting inactivation of the agonists
Example of chemical antagonism:
Binding of Dimercaprol to mercury ion. Dimercaprol is used as an antidote in mercury poisoning.
Physiological Antagonism, involves:
An agonist and antagonist acting at two independent sites and inducing independent but opposite effects.
Histamine and Adrenaline is an example of physiological antagonism. T/F
True.
The type of antagonism involving the action of both the agonist and antagonist on the same site is _______ antagonism
PHARMACOLOGICAL Antagonism
Pharmacological Antagonism consists of two types:
Competitive Antagonism
Non-competitive Antagonism
Example of non-competitive antagonism is:
Action of epinephrine and Dibenamine
Competitive Antagonists include:
Acetylcholine and Atropine
Dose-Response Relationship is dependent on a number of factors,namely:
Adsorption of the drug
Metabolism of the drug
Elimination of the drug
The site of action of the drug in the body
Presence of other drugs or disease
At relatively LOW doses, the response to a drug generally INCREASES in direct proportion to INCREASE in dose. T/F
True
The relationship between the concentration of the drug and the observed effect(response) is graphically represented as a _____ curve
HYPERBOLIC
At higher does of a drug, the amount of change in response to an increase in dose gradually decreases until a dose is reached that produces no further increase in the observed response(I.e) plateau).
T/F
True!
What is the major factor that controls drug effect?
CONCENTRATION OF THE DRUG AT THE SITE OF ACTION
________ is therefore defined as the measurement of the relationship between the quantity/concentration of a substance and it’s overall effect on an organism.
Drug-Response Effect
Response against the logarithm of drug concentration gives a _____ dose-response curve.
SIGMOIDAL
A steep curve that begins to climb even at a small dose suggests a chemical of _____
HIGH POTENCY
The more potent the chemical, the less it takes to kill. T/F
True
Types of Dose-Response curve:
Graded dose-response curve
Quantal dose-effect curve
Characteristics of Graded D-R curve:
• Measured in a single biological unit
• Continuous scale(increase in dose= increase in effect)
• Relates dose to intensity of effect
Characteristics of Quantal Dose-Response:
• Population studies
• all-or-none pharmacological effect
• Relates dose to frequency of effect
Potency is often measured at 50% concentration or dose level.
True/ False
True
