Test 3 Review Flashcards
blood composition
55% plasma, 45% cells and platelets
what is the main transporter in drug distribution
blood
of the 55% plasma, what makes it up?
90% water, 8% plasma proteins, and 2% other
what are the two plasma proteins in plasma?
albumin and globulin
artery
carries blood toward heart
veins
carry blood away from heart
capillaries
between arteries and veins and are site of gas exchange
what % of body is made of water
65%
of the 65%, how much is intracellular and how much is extracellular?
2/3 intracellular, 1/3 extracellular
of the extracellular fluid, how much is plasma and how much is interstitial?
1/4 plasma and 1/4 interstitial
osmotic forces
pull gas into capillaries for exchange
when blood pressure is higher, osmotic forces are…
lower. vice versa
lymphatic veins
pick up leaked fluids from gas exchange within capillaries
lymphatic system
act as “drainage”, they drain leaky fluids from gas exchange back into the cardiovascular system
how does a drug binding to plasma affect the way it crosses the membrane?
only unbound (free) form of drug can cross the membrane. if it binds with albumin it renders it ineffective
discontinuous capillary
most effective
- loosely packed cells, lets medications leak out
- liver, spleen
continuous capillary
tightly packed cells
-brain and muscle
blood-brain barrier
BBB
tight junctions, nothing can leak out of the continuous capillaries into the brain
fenestrated capillary
packed cells with holes
what drugs can pass through the blood brain barrier?
lipid soluble
what is destroyed in a stroke patient, causing hemorrhaging?
the blood brain barrier
unbound/free form of drug
it is not bound to a protein and can pass through the membrane and reach its target
why are lipophilic drugs bad in large doses?
they can accumulate in the tissues by dissolving in the fat
what should you do if someone has a kidney problem?
reduce the dose, because that person will have trouble excreting the medication leading to toxic buildup
6 ways a drug can be eliminated
kidneys, saliva, bile, sweat, breast milk, exhaled air
why should you not chew a pill before swallowing?
saliva may dissolve some of the medication and it won’t travel to the small intestine and be absorbed there where it’s supposed to
most important fluid for excretion
urine
4 kidney functions
water balance, waste removal, maintain pH, and maintain electrolyte balance
nephron
structural unit of the kidney, they are like little filters
bowman’s capsule
structure in a kidney that filters the blood
how much fluid is filtered per day through the kidneys?
180L
how much fluid is reabsorbed into the bloodstream and how much is secreted per day?
179L is reabsorbed, and 1L is secreted (that’s the urine)
excretion
sum of filtration, reabsorption, and secretion processes
glomerular filtration rate
GFR
120 mL/min
if glomerular filtration rate decreases, what happens?
the rate of elimination also decreases because the rate of filtration slowed
renal clearance
amount of medication that is cleared from the plasma
ex) 80% clearance means that 80% of the medication is cleared from the plasma and 20% is retained
what does 0% clearance mean?
none of the drug has been excreted in the urine and is staying in the plasma, possibly being reclaimed
why is the liver not a good source of elimination?
it often reclaims waste and sometimes the drug, making elimination impossible
how are lipophilic drugs excreted?
they can’t be excreted by the kidneys, so first the liver converts them to hydrophilic drugs so the kidneys can absorb them
detoxification
enzymes in the liver getting rid of the toxins by converting them
enzymes in the liver are..?
- proteins
- lock and key relation
- CATALYSTS
catalyst
speeds up a reaction
co-enzyme
aka cofactor
an enzyme that has to be present for a reaction, not a protein
-usually a metal
prodrug
inactive form of a drug that the body must convert to active form
what suffix do enzymes usually end in?
-ase
hydrolase
hydrolysis of substrate
ligase
bond formation
transferase
transfers group between molecules
lyase
elimination and addition reactions
isomerase
rearrangement
oxidoreductase
oxidation or reduction
rate of enzyme activity is proportional to what?
the amount of substrate present
first pass metabolism
liver modifies toxic substances when the drug makes its first stop there
portal vein
vein in the liver that carries drugs to the liver from the small intestine
Phase I reactions
oxidation, reduction, and hydrolysis
-characterized by cytochrome P-450 enzymes
Phase II reactions
conjugate substances for easy excretion
oxidation
taking something out
reduction
adding something in
conjugate
incorporate, join together
what phase of metabolism reaction is affected in the elderly first?
phase I
hepatic vein
takes blood back to the heart after the reactions have occurred in the liver via vena cava
intrinsic activity
ability to initiate response after receptor binding
agonist
same activity as neurotransmitter
antagonist
fits in receptor but has no intrinsic activity
“fits in the ignition but doesn’t start the car”
two types of antagonists
competitive and noncompetitive
competitive antagonist
competes with agonist for receptor site, binds to it, and causes no activity
noncompetitive antagonist
binds somewhere other than the receptor site, changes the shape of the receptor
metabolic pathway
sequence of chemical reactions
- each reaction is catalyzed by a different enzyme
- product of one reaction is the substrate for the next
feedback inhibition
inhibits enzyme in pathway so no product is available to catalyze the next reaction
noncompetitive inhibition
changes the shape of the active site
competitive inhibition
blocks the active site
pharmacokinetics
what the body does to the drug
-absorption and elimination
pharmacodynamics
what the drug does to the body
-adverse effects and pharmacological effects
what is a good indicator of pharmacokinetics?
the drug concentration in plasma-can see how much of drug has been cleared
what happens to drug concentration when an IV is given?
concentration shoots up, then steadily declines over a period of time showing that IV is the fastest route
what happens to drug concentration after an oral dose of medication?
the concentration takes a while to increase, until the maximum value is reached, then steadily declines, showing oral route is slow
bioavailability
Percentage of the administer d dose that reaches systemic circulation intact
what is the bioavailability for IV administration?
100%, highest one
4 sources of poor bioavailability
incomplete absorption or dissolution in the GI tract
decomposition
metabolized by liver
half life
time required to decrease drug concentration by half
therapeutic index
comparison between effective and lethal dose
- narrow index=very little difference between effective and lethal dose, unsafe
- wide index=large difference between effective and lethal dose, safe
rate of elimination depends on what 5 things?
drug clearance, half life, minimum concentration required for efficacy, therapeutic index, and multiple dosing
difference between plasma and serum
plasma is the fluid left on top when anticoagulant (anti-clotting) is added to the blood. serum is left on top when the blood is spun in a centrifuge and allowed to clot
