Test 1: lecture 2-4 Flashcards
name enteral routes of administration
oral
sublingual
rectal
name some parenteral routes of admin
IV
IM
SQ
what are some routes of administration not enteral or parenteral?
nasal
transdermal
interosseus
intraorbital
inhalation
what are some routes that cause instant absorption
nasal
inhale
IV
what enteral route of admin will avoid 1st pass
sublingual
rectal
1st pass: ↑% of drug broken down in liver before it is distributed in the body
what is pKa
pH that the concentration the uncharged and charged are equal
if pKa is 4.4 and pH 4.4 → equal
if pH 3.4 (more acidic) there will be more uncharged then charged
Δ in pKa by 1= x10 change
if pkA is 4.4 at what pH will uncharged and charged be equal
4.4
if pKa = 4.4 and pH 3.4 what will happen
lower pH = more acid/H available
there will be a 10x increase in the non charged molecule
In general, weak acids will be better absorbed from — compartments while weak bases will be better absorbed from — compartments.
acidic
alkaline
fraction of % of drug that enters ciculation after 1st pass effect
bioavailability
if 10 mg PO, 40% absorbed, 75% by 1st pass effect
Bioavilability= 10x0.4= 4 mg to liver
4- (4x0.75)= 1 mg
what is bioavilability of IV?
100%
if 10 mg PO, 40% absorbed, 75% by 1st pass effect
what is bioavailability?
10x0.4= 4 mg to liver
4 - (4x0.75)= 1 mg
1 mg out of 10 mg= 10% or 0.1
weak bases tend to be absorbed from the —
intestine (where pH is more basic >7)
hypothetical volume of plasma into which a drug distributes after bistribution
volume of distribution
how to calculate volume of distribution
(bioavailable dose) ➗ (concentration of drug in plasma after distribution)
is pKa= 4.4 how much of either side
top: 7.4-4.4= 3
↑pH= less H = A-
10^3 x 1= 1000
1+1000= 1001
bottom 3 below pKa= 10^(-3) x 1= 0.001
1+0.001= 1.001
total= 1002.1
what will happen?
weak — will tend to acumulate in an acidic compartment
base
weak — will tend to accumulate in basic compartment
acid
how many L of water per kg of weight?
how many L for a 70kg person?
0.6 L/kg
70 kg person would have 42 L of water space
if Volume of distribution is greater then plasma in a person then —
drug is accumulating in body outside plasma
if Vd=100L/kg
there is only 0.6L/kg of plasma in a person
volume has moved out of plasma.
if Vd= 0.1L/kg what does that mean
plasma in body = 0.6L/kg
smaller= all the drug is distributed inside the plasma
to get theraputic concentration of 0.1mg/L
1 kg patient, Vd=100 L/kg
how much drug to give?
100 (L/kg) x 0.1 (mg/L) x 1 kg = 10 mg
time required to metabolize 50% of drug
half life
T1/2
half life 6 hrs, how much is eliminated in 24 hrs?
— is the ability of the body to eliminate a drug by all routes
clearance
explain
ex: anesthesia
drug will first be very high in brain (central compartment)
then will redistribute into other fatty areas (legs)
this is why you will wake up quickly, but can’t drive, drug has moved comparments but has not been eliminated yet
1st order vs 0 order kinetics
1st order: same fraction of drug is elimiintaed in any given time interval, eventually will get to peak and through dosage that is stable
zero order (alcohol): enzymes are saturated): the same amount of drug is eliminated in any given time period → build up of drug in the system (can’t excrete fast enough)
how does zero order kinetics work
alcohol): enzymes are saturated): the same amount of drug is eliminated in any given time period → build up of drug in the system (can’t excrete fast enough)
why no asprin in cats
low glucuronide synthesis
(takes much longer to degrade Asprin)
how does Vd change in neonate
have more fat= more distribution
enzymes have not formed all the way= different distribution
