Pharmacology Chapter 5 - Pharmacodynamics Flashcards
Pharmacodynamics - def
Study of biochemical and physiological effects of drug….Basically, the study of what drug does to the body and how that happens.
Dose-response relationship (3 things.)
- Determines the minimum amount of drug that can be used.
- Determines the maximal response that drug can elicit.
- Determines how much you need to increase dosage to produce the desired response.
Dose response could be ____ vs ____.
Grades vs. all or none.
Graded means..
dosage is increased as response becomes larger.
All or none means…
response produces only one intensity and cannot be tailored to fit individual.
Basic features of dose-response (3 phases.)
Phase 1 - occurs at low doses - curve is flat because response is too low to measure.
Phase 2 - increase in doses elicits increase in response.
Phase 3 - occurs at high dose - higher dose does not increase response. May elicit toxicity.
Maximal efficacy - def
largest effect that a drug can produce. One drug may have a greater efficacy than another, no matter how much you give (Demerol vs Talwin.)
A drug with high maximal efficacy is/is not always more desirable than a drug with lower efficacy.
IS NOT ALWAYS. We don’t want to give Morphine to treat a headache - that’s what Advil is for!
Relative Potency
Refers to the amount of drug we must give to elicit an effect…..also compares two drugs.
A drug that produces greater effect at a lower dose is more potent.
Why is Relative Potency important?
Important only when potency is so low that huge doses are required for needed effect (rarely happens.) Like, morphine is not superior to Meperidine.
potency of a drug has nothing to do with its maximal efficacy (T/F) ??
True. Drug A & B can be equally effective even though one is more potent.
What does the statement “This drug is very potent” mean?
the drug produces powerful effects (does not mean that the drug produces its effects at a low dose.)
Receptor - def
Any functional molecule in a cell to which a drug binds to produce its effects.
How many receptor kinds are there?
4
4 Types of Receptors…
Cell Membrane embedded enzymes, Ligand-gated ion channels, G-protein coupled receptor, transcription factors.
Cell membrane embedded enzymes…
Span full width of membrane. Response within seconds. Ligand binding domain is external and catalytic binding region is on the inside of membrane.
Ligand-gated ion channels
Span membrane, response extremely fast. Regulates flow of ions in and out of cells. When ligand bind channels open…allowing ions to flow either inward or outward.
G-protein coupled receptor systems.
Have three components - the receptor, G protein, effector.
domain is located in a pocket accessible from the cell surface.
Response is rapid.
Transcription factors
Found with the cell rather than on the surface.
regulate protein synthesis through RNA synthesis.
Some drug interactions Do/Do Not involve binding to receptors.
DO NOT. They act through simple physical or chemical interactions with other small molecules. Examples? Antacids, Antiseptics, Laxatives, etc.
Drug can __ or __ normal hormone/neurotransmitter/molecule binding.
Mimic (increase response) or block (decrease response.)
Drugs can only ____ or ____ the action of the body’s own regulatory molecules.
Mimic or block.
Drugs can/cannot give new functions to the cell.
Cannot
Can a drug theoretically be made to alter the rate of any biological process for which receptors exist?
YES.
Even though a drug is selective for one receptor, is it possible for that drug to produce nonselective effects?
YES, is a single receptor is responsible for several physiological processes.
Selectivity does/does not guarantee safety?
DOES NOT.
Simple Occupancy theory - def
Intensity of response to a drug is proportional to the number of receptors occupied by that drug.
Maximal response occurs when all available receptors…..___
have been occupied.
Modified occupancy theory (two parts.)
Affinity Binding and intrinsic binding.
Affinity Binding - def
Strength of the attraction between drug and the receptor. The greater the affinity, the greater the potency. Drugs with low affinity require higher concentrations to bind to receptor.
Intrinsic activity - def
ability of a drug to activate its receptor - High intrinsic activity relates to high maximal efficacy. 2 drugs can bind to same # of receptors with different intensities of response.
Agonist - def
molecules that activate receptors (mimicry.)
Agonist has high….___
high affinity and high intrinsic activity.
Antagonists - def
produce effects by preventing receptor activation by endogenous regulatory molecules and drugs. Has high affinity for receptor but NO intrinsic activity.
Partial Agonists (Partial Antagonist?)
has moderate intrinsic activity & therefore the maximal effect that a PA can produce is lower than that of a full agonist.
ED-50 - def
Effective dose 50. Dose required to produce a defined therapeutic response in 50% of the population = middle of the frequency distribution curve.
Therapeutic index -
measure of a drug’s safety. Defined as the ratio of drugs LD50 to its ED50.
LD50 - def
dose that is lethal to 50% of the animals treated.
A ___ therapeutic index indicated that a drug is unsafe while __ indicates that a drug is relatively safe.
small/large.
