Lecture 2 Notes-Principles of Pharmacology and
We are up to chapter 3 now.
The most important factors that determine a drugs effects is the concentration of
the drug and its rate of absorption.
Dose is the quantity of drug that is administered at one time. The greater the body
weight of the subject, the greater the drug amount needed to achieve the same effect
as on a normal person.
One never sees a perfect linear relationship between the dose of a drug and a
When you have a less linear function you will see a more sigmoidal function.
Some species are much more sensitive to small concentrations of a drug such as
rats. It could also be that the drug may have different effects on different species.
Drug actions tend to be active longer in infants and the elderly because the
metabolize drugs at a much slower rate.
The threshold dose is the minimum amount of the drug required to produce any
desired effect of the drug.
The maximal effect is the minimum dose of the drug required to exhibit the
maximum effect of the drug.
ED50- the dose that produces the desired pharmacological effect is 50% of the
LD50- a dose that if administered, would have lethal effects.
Generally, you want the LD50 dose-response function to be significantly different; or
way to the right on the x-axis.
Why might it be the case that you wouldn’t administer the maximal dose of the
drug? didn’t hear the answer.
Efficacy relates to the maximal effect. What is the maximal effect of the drug and
how does that maximal effects compare to other drugs.
Potency- how little of the drug, relative to another, is required to achieve the desired
Antagonism- the reduced effect of one drug in the presence of another
Synergism- the greater effect produced by two drugs administered together.
Pharmacodynamics are the physiological effects of the drug
Pharmacokinetics- what does the body do the drugs for them to have an effect on
Absorption- entry of drug in to the blood system
Distribution- the drugs gaining access to its binding sites
Metabolism- the processes involved in breaking down the drug; a lot of drugs are
actually metabolized before they reach their binding sites.
Excretion- disposal of the drug from the system.
If there is no drug present in the blood then at the site of injection of absorption the
drug will be absorbed at a much higher rate than if there is a drug already present.