Pharmacodynamic Principles - 2 Flashcards
Action of one drug is facilitated or increased by use of another drug
Synergism
Synergism can be which?
1- additive.
2- Supra-additive / potentiation
The effect of two drugs is in the same direction and adds up
Additive synergism
What are the advantages of additive synergism?
1- side effects of the combination may not add up.
2- combination is better tolerated than higher dose of one drug.
Give 2 examples of additive synergism?
1- aspirin + paracetamol.
2- glibenclamide + metformin
Effects of the combination is greater than the individual effect of the drugs?
Supra-additive synergism.
When does Supra-additive synergism occur?
When one drug is inactive, but enhances the effect of the other.
Give 2 examples of Supra-additive synergism?
1- levodopa + carbidopa.
2- acetylcholine + physostigmine.
One drug decreases or abolishes the action of another drug
Antagonism
List the 4 types of antagonism?
1- physical antagonism.
2- chemical antagonism.
3- physiological / functional antagonism.
4- receptor antagonism.
Give an example of physical antagonism?
Charcoal in alkaloid poisoning.
Give an example of Chemical antagonism?
Chelating agents complex toxic metals.
Give an example of physiological/ functional antagonism?
Histamine and adrenaline on bronchial wall
Give an example of receptor antagonism?
Acetylcholine and atropine on M receptor.
One drug blocks the receptor action of the other - it is selective in nature
Receptor antagonism
List the 3 types of receptor antagonism?
1- competitive antagonism.
2- non - competitive antagonism.
3- non - equilibrium antagonism.
Extent of shift in competitive antagonism depends on what?
Concentration of the antagonist.
List the 10 factors that affect drug action?
1- body size.
2- age.
3- sex.
4- ethnicity.
5- genetics.
6- routes of drug administration.
7- environmental factors and Time of administration
8- physiological factors.
9- pathological states.
10- other drugs.
Which factors affecting drug action influences the concentration of the drug attained at the site of action?
Body size.
How do we calculate individual dose using BW?
Individual dose = BW(kg)/70 x average adult dose
How do we calculate individual dose using BSA?
Individual dose = BSA(m2)/1.7 x average adult dose
Individual dose using BSA is used for which type of drugs?
Anti cancer drugs
The dose of a drug for children is often calculated from the _____ dose
Adult
What is young’s formula for calculating children’s dose?
Child’s dose= age/(age+12) x adult dose