0401 - Pharmacology - Pharmacodynamics Flashcards
What is pharmacodynamics and pharmacokinetics
Pharmacodynamics: this can be summarized as the study of the effect of the drug on the body. It involves the examining:- Biochemical and physiological effects of drugs- The effects of drugs on microorganisms- The mechanisms of drug action- The relationship between drug concentration and effect on the bodyPharmacokinetics: this effectively deals with the fate of substances that are administered externally to a living organism
What are some examples of drug targets
Almost always drugs will act on protein targets. Examples of these include:- Enzymes- Carriers- Channels- receptors
What is the value of having a semi logarithmic graph
The semi logarithmic graph changes the scale on the x-axis so that the smaller values of the drug concentration are given a larger portion of the x- axis and the gradual change in the drug target binding is more visible. This is made evident in graph B above.
Explain the difference between potency and efficacy
Potency: this is a measure of the drug’s efficacy at a given concentration. The more potent a drug, the more effective it will be at a lower concentration. We can compare potency by comparing the quantity of drug that must be administered in order to reach 50% of its maximum efficacy.Efficacy: this is the magnitude of the response as a result of the drug administered. It is a measure of the drug achieving its goal. E_max is the maximum possible effect of the drug on the body
What are agonists and antagonists
Agonist: this is a chemical that binds to a receptor and keeps the receptor in an active state. It can be a drug or an endogenous molecule.Antagonist: this is a chemical which inhibits the action of an agonist. It has no effect in the absence of an agonist.
What is a partial agonist
These are drugs that bind to a receptor but only have a partial effect on the receptor compared to the full agonist. When mixed with a full agonist, a partial agonist will have the effect of reducing the effect of the full agonist. A very poor partial agonist can function as a competitive antagonist.
Explain the antagonist effect on receptor occupancy by an agonist
There are two cases to consider here.Reversible competitive antagonism: this refers to the case where the antagonists binding to the receptor is reversible. For this reason, the fractional occupancy of the receptor by the agonist can be returned to normal, simply by increasing the concentration of the agonist. The higher the concentration of the antagonist, the more agonist is required to return the functionality to normal. This will reduce the potency of a drug.Irreversible competitive antagonism: this refers to the case where the antagonist will bind to the receptor in a reaction that cannot be reversed. Increasing the agonist concentration will increase functionality, but will not return the receptor to maximum fractional occupancy by agonists. If enough antagonist is present the fractional occupancy can remain at zero. This will reduce the efficacy of a drug.
