Pharmacology Flashcards
define pharmacology
the branch of medicine concerned with the uses, effects, and modes of action of drugs
define pharmacokinetics
the actions of the body on drugs
define pharmacodynamics
the actions of drugs on the body
what is ADME?
- absorption
- distribution
- metabolism
- elimination
what is an agonist?
- a drug or a natural ligand that binds to and activates receptors
- sometimes selective and sometimes not
understand what is going on in this figure
![](https://s3.amazonaws.com/brainscape-prod/system/cm/201/947/585/q_image_thumb.png?1480367661)
what is an antagonist?
- bind to receptors but do not activate the receptor
- instead, it interferes with the agonist, typically causing a shift to the right
- *in order for the receptor to activate in the presence of antagonists, there must be more agonists than antagonists
what is an allosteric activator?
- aka positive allosteric modulator
- binds a receptor site separate from the agonist site
- potentiates effects
what is an allosteric inhibitor?
- aka negative allosteric modulator
- binds receptor site separate from agonist site
- noncompetitive
- actions are often reversible
describe what is going on in this figure
![](https://s3.amazonaws.com/brainscape-prod/system/cm/201/948/263/q_image_thumb.png?1480368197)
- Ra = active receptor, even in absence of drug (i.e., produce small observable effect referred to as constitutive activity)
- Ri = inactive receptor, even if paired with most drugs; the inactive form is usually favored
- D = drug
- in the absence of drugs, the two isoforms are in equilibrium, and Ri is favored
describe what is happening in this figure
![](https://s3.amazonaws.com/brainscape-prod/system/cm/201/948/435/q_image_thumb.png?1480368384)
- the full agonist has a much higher affinity for the Ra conformation, and mass action thus favors the formation of the Ra - D complex with a much larger observed effect
- the partial agonist produces lower response at full receptor occupancy than full agonists
- intermediate affinity for both Ri and Ra
- do not stabilize Ra - D as well as full agonists
- the inverse agonist has greater affinity for Ri, reduces constitutive activity, and may produce a contrasting physiologic result
- the conventional antagonist has equal affinity for Ra and Ri, and thus no change in constitutive activity
what is EC50?
the drug concentration where the effect is half maximal
what is Kd?
the drug concentration where the receptor occupancy is half maximal
what is Emax?
maximum binding of a drug, resulting in the maximum effect of the drug
what is IC50?
- the concentration of drug where 50% of effect is blocked
- think about when there is no antagonist present, the effect will be very high, but once you start adding antagonists, the effect will be reduced
what happens to the EC50 when a competitive antagonist is added to an agonist?
- the EC50 will shift right
what happens to the EC50 when a noncompetitive antagonist (or irreversible antagonist) is added to an agonist?
- the EC50 does not shift
what are the plateau and threshold doses?
- plateau - dose required for maximum effect
- threshold - smallest does that causes an effect
what are spare receptors?
- receptors are spare for a given pharmacologic response if it is possible to elicit a maximal biologic response at a concentration of agonist that does not result in occupancy of the full complement of available receptors
- At D and E, the spare receptors have been used up
![](https://s3.amazonaws.com/brainscape-prod/system/cm/201/950/203/a_image_thumb.png?1480369947)
understand this figure
![](https://s3.amazonaws.com/brainscape-prod/system/cm/201/950/487/q_image_thumb.png?1480370936)
- note that the full agonist is present at a single concentration
describe the general drug-receptor interactions of additive, synergistic, and antagonistic drugs
- additive: drug effect = sum of individual effects
- synergistic: drug effect is greater than the sum of individual effects
- antagonistic: drug effect is less than the sum of individual effects
describe a chemical antagonist
- does not involve a receptor
- example: protein that is positively charged at physiologic pH counteracting the effects of a drug that is negatively charged by ionic binding that makes the other drug unavailable to interact
describe a physiological antagonist
- involves endogenous regulatory pathways mediated by different receptors
what is efficacy?
- the number of receptors that must be activated to yield a maximum response
- a drug with high efficacy needs to stimulate only a small percentage of receptors, whereas a drug with lesser efficacy has to activate a larger proportion of receptors
what is potency?
- the relative concentrations of two or more drugs that produce the same drug effect
- this effect usually chosen is 50% of the maximal effect and the dose causing this effect is called the EC50
what two factors govern drug action?
affinity and intrinsic activity
what is the therapeutic index?
dose of the drug that causes toxicity divided by the dose of the drug that causes therapy
TI = TD50/ED50
what is the therapeutic range?
range in dose between toxicity and therapy
what is meant by a drug with a wide margin of safety
large difference between toxic dose and therapeutic dose
the amount of drug that gets to its target is inversely proprotional to what two things?
- distance from site
- amount of tissue the drug must pass through
what is parenteral administration?
administration by means other than intestine or GI tract
what is intravenous administration?
- administration directly into blood circulation
- type of parenteral administration
- very rapid, easier to titrate, avoids irritation, overdoses may have effects too immediate to reverse
what is intramuscular administration?
- administration into musculature
- type of parenteral administration
- prompt absorption, uniform absorption of solutions, large volumes possible, sometimes painful