Week 2- pharmacodynamics Flashcards
Define pharmacodynamics.
Study of what drugs do to the body and how they do it.
Discuss the three phases of the dose-response curve.
Phase 1 – no measurable response
Phase 2 – increased dose increases response
Phase 3 – No further increase in response
Define maximal efficacy.
Largest effect which can be produced by a drug.
Define relative potency.
Amount of drug needed to produce an effect. A potent drug produces effects at low doses.
The binding of a drug to a receptor does what to body processes?
Turns processes on or off.
How does a cell membrane-embedded enzyme work?
Binding to the receptor on the cell membrane activates an enzyme inside the cell.
How do ligand-gated ion channels work?
Binding to the receptor on the cell membrane activates ion channels.
How do G protein-coupled receptors work?
Binding to the receptor activates the G protein which activates the effector.
Where are transcription factors found? How do they work?
On the DNA in the cell.
Activate transcription of messenger RNA to make protein.
Which type of receptor is the fastest?
Ligand-gated ion channels
Explain the simple occupancy theory of drug-receptor interaction.
The intensity of the response is determined by the number of receptors occupied.
Define affinity.
The strength of attraction between drug and receptor.
Define intrinsic activity.
The ability of the drug to activate a receptor upon binding.
Define agonists.
Drugs which bind to the receptor and mimic the action of endogenous regulatory molecules.
Explain the actions of full and partial agonists.
Full agonists have high intrinsic activity and produce a full effect. Partial agonists have a moderate intrinsic activity and produce a partial effect.
Define antagonists.
Drugs which bind to the receptor and block the action of endogenous regulatory molecules.
Explain the difference between competitive and noncompetitive antagonists.
Competitive antagonists bind reversibly, and a maximal response can be achieved by increasing the concentration of the agonist. Noncompetitive antagonists bind
irreversibly, and the maximal response cannot be achieved.
Explain up and down regulation.
Down regulation includes decreasing the number of receptors &/or response. Up regulation includes increasing the number of receptors &/or response.
List three receptorless drugs.
Antacids, antiseptics, saline laxatives.
Define the average effective dose (ED50).
Dose producing a therapeutic response in 50% of the population.
Define the therapeutic index. Is a large index safer or more dangerous?
The ratio of the lethal dose to the average effective dose. Safer.
What is the relationship between the number of drugs a patient takes and the risk of drug-drug interactions?
The more drugs the patient takes, the higher the risk of drug-drug interactions.
List three types of drug-drug interactions.
Potentiative, inhibitory, unique.
How may laxatives affect absorption?
Laxatives can decrease absorption by increasing drug passage.
Decreasing cardiac output may do what to drug excretion?
Decrease drug excretion.
What organ system is responsible primarily for drug metabolism?
Liver
What happens to drug levels of drugs metabolized by the P450 system when the system is inhibited? Induced?
When metabolism is inhibited in the P450 pathway, drugs being metabolized by that pathway are not metabolized as rapidly and plasma drug levels increase. Conversely, when the system is induced, metabolism of those drugs occurs more rapidly, decreasing plasma drug levels.
What 4 processes happen with the induction of PGP (P-Glycoprotein)?
Decreased intestinal absorption, decreased fetal exposure, decreased brain exposure, increased elimination of drugs into bile or urine
Calcium may do what to the absorption of tetracycline?
Decrease absorption.
How does grapefruit affect the absorption of drugs from the intestines?
How long does grapefruit exert this effect?
Grapefruit inhibits CYP3A4 metabolism in the intestinal wall for 72 hours, so more drug is absorbed.
How would you administer a drug on an empty stomach?
1 hr before or 2 hours after a meal
