2nd Exam Flashcards
What is Pharmacodynamics?
Study of how drugs affect living tissues
How can pharmacodynamics effects be measured?
By clinical or biochemical means
Ex: BP drops post ACE inhibitors
Ex: Blood glucose drops post insulin
What do outcome effect(s) of a drug at the action site involve?
Receptor binding
Post-receptor effects
Chemical interactions
Chemical interactions of drugs
Drug has effect-
No change to cellular function
No binding to a receptor
Ex: Antacids- Cholestyramine to bind bile acids in GI tract
What is mechanisms of action?
Manner in which drug affects target tissue.
Drugs either enhance or block cellular functions
The 3 ways how drugs produce effects.
Drug-receptor interactions
Drug-enzyme interactions
Other, nonspecific interactions
What is a drug receptor?
Body tissue where drug works -Site on cell membrane or in cell with affinity for drug -Macromolecular component of tissue Max effect of drug occurs here Cell function altered
What is affinity?
Drug attracted to tissue/receptor
-Strong affinity = less drug needed for action
What is efficacy?
Ability to start biologic activity once bound to cell
How effective the drug is at producing desired effect
Receptor site on cell has strong affinity for drug
What is an agonist?
Binds with receptors for therapeutic response
Enhances a normal biologic function
Drug fits into specific area on/in cell (key into a lock)
Initiates biochemical & physiologic changes
*Produces an intended effect
What is a partial agonist?
Partial binding at site
Some efficacy
What is an antagonist?
Blocks receptors on cell
Joins w/receptor, prevents agonist from working
Keyhole blocked; key can’t get in
Inhibits or counteracts effects of other drugs OR undesired cellular processes
What is competitive antagonist?
Attracted to same site as agonist
Inhibits action of agonist
*Reversible
What is noncompetitive antagonist?
Combines to different part of receptor & inactivates receptor = agonist ineffective
*Irreversible
Common protein targets for drugs:
Enzyme
Carrier molecules
Ion channels
Receptors
Drug enzyme interactions
Enzymes are catalysts, start biochemical reactions
Occurs when drug has similar chemical make-up to substrate an enzyme is attracted to
Enzyme action blocked or stimulated
-Pharmacodynamic reaction
-Can lead to drug toxicity if drug action blocked
Nonspecific drug interactions
Drug effect occurs in various ways:
- Emollient: blocks tissue exposure to outside world
- Radiographic contrast: alters atomic number of tissues
- Accumulate in cell/cavity & interfere with cell function
What is emollient?
It blocks tissue exposure to outside world
What does radiographic contrast do to tissues?
It alters the atomic number
What is potency?
Concentration of drug required to produce desired effect. Related to drug/receptor interaction.
What is half life?
Time for serum drug concentration to drop by ½
Stable per drug, unless metabolism or excretion abnormal. Ex: patient does not process drug normally
Dose usually does not alter this
What are other names for half life?
Biologic half-life, half-life of elimination
What is the serum concentration drug profile?
Graph that shows the life of a drug from administration to elimination.
What is the onset?
Time between administration & first sign of drug effect
What is the duration?
Onset of action to end of response
What is the termination?
Drug no longer seen
What is the minimum effective concentration?
Lowest plasma concentration to produce effect
What is the peak serum concentration?
Max plasma concentration
What is the therapeutic range?
Ideal plasma concentration w/o toxicity
What is the toxic level?
Plasma concentration leading to toxicity
What is Emax?
Max effect of a drug based on a specific measured parameter
What is EC50?
Drug concentration at a steady state that produces half the max effect
What is the hill coefficient?
Slope of relationship between drug concentration and drug effect
What is the therapeutic index?
Measure of drug safety
Ratio: LD50 / ED50 = TI
Lethal dose to kill 50% of population over effective/therapeutic dose to kill 50% of population
Ratio of 1 = lethal drug (don’t want)
What is an adverse effect?
Any unwanted effect
What is a side effect?
Predictable pharmacologic action but not the intended action
Action on non-target tissues
May have positive or negative outcomes
Nontoxic
Ex: Nausea, drowsiness, constipation, less anxiety, reduced itching
Are side effects always an adverse effect?
No
What is toxicity?
Dose related
Higher dose = greater chance of toxic levels in plasma
Can happen with iodinated contrast
What is an allergic reaction?
Immune system response
Due to repeated exposures to drug or chemically related compound
Body vs. drug
Not dose related
What is a drug-drug interaction?
An adverse effect
3 examples of a drug-drug interaction:
- Increased agonistic, antagonistic or synergistic response by 2+ drugs
- Synergism
- Chemical incompatibility
What is synergism?
When one drug acts with another = more response than expected
What is chemical incompatibility?
One drug may destroy actions of another
Two mix and precipitate out (Chelation effect)
What happens with increased agonistic, antagonistic, or synergistic response by 2+ drugs?
One drug alters metabolism of another
Possible toxic levels
What is an idiosyncratic reaction?
An adverse effect
Abnormal response to drug caused by individual genetic differences
Is unexpected or exacerbated effect
What are some factors that influence drug action?
Food intake
Drugs taken at the same time
-Synergistic rxn (increase each others function)
-Additive rxn (Have add on reaction)
What conditions can cause a normal dose of a drug become toxic?
Impaired metabolism or excretion/elimination of drug (kidney failure)
List some types of effects drugs can have:
Intended, side effects, adverse, toxic, allergic reaction
T or F: Drugs create new biologic functions?
False
What graph shows the life cycle of a drug?
Serum concentration profile
