Pharmacology I Flashcards
define pharmacology
the branch of medicine concerned with the uses, effects and modes of action of drugs
define pharmakinetics
the actions of the body on the drugs
define pharmadynamics
the actions the drugs have on the body
what does ADME mean?
A absorption
D distribution
M metabolism
E elimination
Drug-receptor interactions:
Agonist
drug or natural ligand
activates the receptor
sometimes selective and sometimes not
Drug-receptor interactions:
anatgonist
*bind to receptor but do not activate
interfere with agonist
typically shift dose-response to the right
Drug-receptor interactions:
allosteric activator
postitive allosteric modulator
*binds to receptor site separate from agonist site
potentiates effects
Drug-receptor interactions:
allosteric inhibitor
negative allosteric modulator
bind receptor site separate from agonist site
*noncompetitive
*actions often reversible
in the absence of drugs, the two isoforms are in equilibrium and what is favored
receptor inactive
what is a full agonists
has a much high affinity for the active receptor conformation and mass action thus favors the formation of the active receptor bound to the drug complex with a much larger observed effect**
Partial agonists
produce lower response at receptor occupancy than full agonist
- intermediate affinity for both inactive and active receptor(less affinity than full agonist)
- does not stabilize active receptor-drug complex as well as a full.
Inverse agonist
have a greater affinity for inactive receptor, reduce constitutive activity, and may produce a contrasting physiologic result
conventional antagonist
equal affinity for the active and inactive receptor and thus no change in constitutive activity.
**flat line on graph
what is the effective concentration 50?
drug concentration where effect is half the maximum
what is the Kd?
drug concentration where receptor occupancy is half the maximum
what causes a shift to the right in the EC50?
agonist and a competitive antagonist
what causes a drop in the agonist effect?
agonist and a noncompetitive antagonist
**no shift in EC50
what is the plateau?
the max effect of the agonist effect
what is the threshold?
the lowest dose that causes a measurable effect
receptors are spare for a given pharmacologic response if it is possible to do what?
elicit a maximal biologic response at a concentration of agonist that does not result in occupancy of the full complement of available receptors.
-so after one dose you can give another dose and get a maximal effect again due to spare receptors
additive drug-receptor interactions
sum of the two drugs is equal to the two drugs
synergistic drug-receptor interactions
the sum of the two drugs is greater than the sum of the two drugs
antagonistic drug-receptor interactions
additive effect is less than the sum of the two drugs
eg. antidote
chemical antagonist
does not involve receptor
eg. 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
physiological antagonist
involves endogenous regulatory pathways mediated by different receptors
what does efficacy mean?
refers to the number of receptors that must be activated to yield a maximum response.
A drug with high efficacy needs to stimulate only a small or large percentage of receptors?
small percentage
**lower dosing needed
vertical response
a drug with a lesser efficacy (but still not considered to be a full agonist) has to activate a small or larger proportion of receptors?
larger percentage of receptors
**higher dosing needed
verticle response
what does potency mean?
the relative concentrations of two or more drugs that produced the same drug effect. This effect is usually chosen is 50% of the maximal effect and the dose causing this effect is called the EC50
is potency a vertical or horizontal relationship?
horizontal
what is the therapeutic index?
toxic dose/effective dose
you want a wide range and a big number
what is the therapeutic range?
the dose between toxicity and therapy
what is margin of safety?
the amount of drug that is lethal to 1% divided by the amount of drug that causes beneficial effect in 99%
a wide margin of safety means what?
a large difference between toxic dose and therapeutic dose
what does parenteral mean?
not by way of intestine or GI tract
intravenous
very rapid, easier to titrate avoids sub. cutaneous irritation, overdoses may have effects too immediate to reverse
intramuscular
prompt absorption (5 minutes owing to blood flow) large volumes possible, sometimes painful
subcutaneous
adsorption may be less rapid (i.e. 15 minutes)
smaller volumes than intramuscular, sometimes painful
enteral
by way of the intestine or GI
Buccal or sublingual
oral
rectal
buccal or sublingual enteral
under tongue or incheek
oral enteral
most common and convenient, onset of effects in 30 min.
most unpredictable
absorption via duodenum
first pass metabolism
rectal enteral
solution(enema) or suppository
less first pass than oral
the initial distribution of drug into tissues is determined by what?
rate of blood flow
the concentration of drug at a particular site is related to what?
affinity
plasma binding proteins and gastric emptying time can play roles T/F
true
what is the fastest way to deliver a drug?
inhalation
topical delivery
applied to a surface
transdermal delivery
onset of effect in 15 min
slow and sustained
nicotine patch
what is a loading dose?
a boosted initial dose to get the concentration higher than the therapy level to start immediate effects
what is a maintenance dose?
doses that keep the concentration in the therapy range or window
