Pharmacokinetics & Pharmacodynamics Flashcards
what are the four parts to the phamacokinetic phase?
- absorption
- distribution
- metabolism
- excretion
What are the three parts to the pharmacodynamic phase?
- receptor binding
- postreceptor effects
- chemical reaction
Drug movement from GI tract into bloodstream
drug absorption
what does drug absorption require?
- -disintegration
- dissolution
breakdown of oral drug form into small particles
disintegration
process of combining small drug particles with liquid to form a solution
dissolution
enteral
by mouth
what are the different absorption methods?
- passive transport
- active transport
- pinocytosis
most drugs are taken by this route
enteral
resist disintegration in the gastric acid of the stomach, may be delayed in onset
EC Enteric Coated Drugs
Where are EC drugs absorbed at?
small intestine
what factors affect drug absorption?
- bloodflow, pain, stress, gastric pH
- food texture, fat content, temperature
- route of administration
less blood flow =
less absorption
shock, BP bottoms out =
decreased blood absorption
which route of administration has the fastest onset of action?
IV
Which route of administration is slower, dependent on blood flow area?
SubQ
Which route of administration has a slow onset and is unpredictable?
Oral
passive transport occurs through
- diffusion
- facilitated diffusion
drugs move across the cell membrane from an area of higher concentration to lower concentration
diffusion
relies on a carrier protein to move the drug from an area of higher concentration to lower
facilitated diffusion
which transport does not require energy?
passive
requires a carrier such as an enzyme or protein to move the drug against a concentration gradient
Active Transport
energy is required for which transport?
active
cell carries drug across membrane by engulfing drug particles
pinocytosis
after absorption of oral drugs from the GI tract, they pass from the intestinal lumen via what?
portal vein
what organ metabolizes drugs?
Liver
List drug movement in order starting with GI tract
- portal vein
- liver
- body
when the liver metabolizes a drug to an inactive form and is excreted, reducing the amount of active drug available to exert a pharmacologic effect
first pass affect or first pass metabolism
affected by the first past affect
bioavailability
% of administered medication that reaches systemic circulation (amount of drug actually available for use)
bioavailability
factors that affect bioavailability
- absorption
- first pass metabolism
- drug form
- route
- gastric mucosa and motility
- administration with food and other drugs
- changes in liver metabolism
decreasing liver function increases what?
bioavailability
movement of drug from circulation to body tissues
drug distribution
what are the influencing factors of drug distribution?
- protein binding
- free drugs
- blood brain barrier
as drugs are distributed in the plasma, many bind with
plasma proteins
list the different plasma proteins
- albumin
- lipoproteins
- Alpha-h acid-glycoprotein
what happens if a drug binds to protein?
it doesn’t work
the portion of the drug bound to protein is inactive because
it is not able to interact with tissue receptors and is unable to exert a pharmacologic effect
portion of drug that is not bound to protein and is free
free drug
able to exit blood vessels and reach site of action causing a pharmacologic response
free drug
blood vessels of the brain made of special endothelial lining where the cells are pressed tightly together and protects the brain from foreign substances
blood brain barrier
what drugs are able to cross the blood brain barrier?
drugs that are highly lipid soluble and of low molecular weight such as benzo’s
can drugs cross the placenta?
yes
drug metabolism is also known as
biotransformation
process of body chemically changing drug into form that can be excreted
drug metabolism
if the liver function is decreased, what happens to the drug effects?
increases
biologically inactive compound which is metabolized into the body and to produce a drug
prodrug
used to improve drug delivery, decrease toxicity or to target specific cells or tissues
prodrug
example of prodrug
codeine
why is codeine and example of a prodrug?
- little activation of opioid receptors as codeine
- metabolized into morphine by liver
- morphine activates opioid receptors
period of time required for concentration or amount of drug in body to be reduce by one-half
half life
affected by metabolism and elimination
half life
used to determine dosing interval
half life
decrease in liver and kidney function leads to an increase or decrease in half life?
increase
if you have a long half life, do you have to give a medication as often?
no
long half life leads to increase in
compliance
plateau drug level
steady state
steady state takes how many half lives?
4
large initial dose or series of doses to rapidly achieve therapeutic concentration and steady state
loading dose
example of loading dose
Z Pac
what are different ways that drugs are excreted?
- kidney
- liver
- lungs
- saliva, sweat, and breastmilk
what is the main route of drug excretion?
kidneys
how are drugs excreted from the liver?
through bile
how are drugs excreted through the lungs?
exhaled respiratory system
liver dysfunction leads to
decreased metabolism
kidney dysfunction leads to
decreased excretion
urine pH affects
excretion
acidic urine promotes elimination of
weak base drugs
alkaline urine promotes elimination of
weak acid drugs
which drug is excreted rapidly in alkaline urine?
salicylic acid (aspirin)
treatment of salicylate toxicity includes
IV admin of sodium bicarbonate
common tests to determine renal function
- creatinine
- BUN
study of the way drugs affect the body
pharmacodynamics
desirable response
primary effect
desirable or undesirable response
secondary effect
primary effect morphine
pain relief
secondary effect of morphine
constipation (undesirable)
diarrhea (desirable)
primary effect benedryl
treat allergy
secondary effect benedryl
sleep (undesirable) bed time (desirable)
how much drug to get significant response
potency
no matter how much more you take of a medication it won’t increase therapeutic effect
maximal efficacy
amount of med to give to produce effect
therapeutic dose
difference between potency and maximal efficacy
therapeutic index
ED50
therapeutic dose
give drug to 100 people and only half have a response to this. this is what type of dose?
therapeutic
give drug to the same 100 people and half show toxicity, this is what type of dose?
toxic
with narrow effect the nurse should monitor
drug toxicity and blood levels
what medications have a narrow effect?
- warfarin
- digoxin
- phenytoin
time it takes drug to reach minimum effective concentration
onset
highest concentration in blood
peak
small amount of drug necessary to get effect of drug
minimum effective concentration
length of time taken for a drug to exert therapeutic effect
duration
time to take next dose to keep wave going
term of action
measure taken after drug administration to monitor for toxic levels
peak drug level
measure before next dose, lowest drug level gets
trough
peak level of IV
30-60minutes
peak level of oral drug
3
receptor theory
drugs bind to receptors
drugs bind to receptors to inactivate a receptor by
blocking a response
activate receptors
agonists
prevent receptor activation
antagonists
block response
antagonist
affect multiple receptor sites
nonspecific drugs
affect multiple receptor types
nonselective drugs
decrease response to drug and need to increase dosage to get effect
tolerance
suddenly drug stops working after one or several doses
tachyphylaxis
predictable, not signs of toxicity
side effects
what is good for patient to know of drugs
side effects
undesirable effects, unexpected more severe, can occur at normal dosage
adverse reaction
drug level exceeds therapeutic range, too much of the drug and drug accumulation (liver or kidney dysfunction)
drug toxicity
highest risk in elderly, 1 in 5
drug interaction
when one drug affects another
drug interaction
what people are at risk for drug interactions?
- chronic health
- patient taking a lot of medication
- those taking different dietary supplements
- those who see more than 1 provider
- patient who use multiple pharmacies
changes occurring in absorption, distributions, metabolism, and excretion
phamacokinetic interactions
changes gastric pH
absorption
increase or decrease gastric emptying time
absorption
cause formation of drug complexes
absorption
induce production of hepatic enzymes
metabolism
metabolism can inhibit production of hepatic enzymes which means
drugs are metabolized slowly
what are impotent inhibitors that increase toxicity
- alcohol
- food
- grapefruit juice
diuretics cause what?
electrolyte imbalance
electrolyte imbalances cause what?
- decrease in cardiac output
- decrease of blood flow to kidneys
- decrease of excretion of other drugs
sum of effects of two drugs
additive
example of additive drugs
- hydralazine and nitro
- both cause vasodilation and cause low BP
effect is much greater than affects of either drug alone
synergistic
example of synergistic
amoxicillin and coagulonate (antibiotics)
one drug reduces or blocks effects of other drug
antagonistic
example of antagonistic
- desirable nalaxone (narcan) (opioid overdose) blocks opioid receptor
- protamine sulfate (blocks heparin)
food may increase, decrease or delay drug response
drug nutrient interactions
drugs may cause misinterpretation of drug results
drug laboratory interaction
skin reaction caused by sunlight exposure
drug induced photosensitivity
cause BP to rise to dangerous levels
MAOI (monoamine oxidase inhibitor)
Is alcohol a drug?
yes
