Pharmacokinetics Flashcards
advantage of rectal route
limited first pass metabolism
advantage of sublingual route
avoids first pass metabolism
disadvantage inhalation route
variable systemic distribution
most common way for drugs to cross membrane
simple diffusion
P glycoprotein transports drug ___ of cells
OUT of cells
pKa
the pH where exactly 1/2 of weak acid is ionized
weak acids weak bases: which better absorbed in stomach
weak acids
Ka
rate constant for absorption
S
salt factor
F
bioavailability
how is F measured
(area under the curve) oral / (area under the curve) IV
how is amount absorbed measures
S x F x Dose = amount absorbed
tissues with highest CO
liver
kidneys = muscle
what is alpha
percent of drug unound
how is concentration in plasma measured
(S x F x Dose) / volume of distribution
how is volume of distribution measured
amount of drug in body / amount of drug in plasma
effect of phenobarbital and carbamazepine on CYP450
induces it and speeds up metabolism of other drugs
effect of erythromycin and ketoconazole on CYP450
inhibitors, slow metabolism of other drugs
effect of grapefruit juice on bioavailability of other drugd
it INCREASES their bioavailbility by inhibiting CYP450
what is glucurodination and what phase does it happen in
adding a charge to the drug
- phase II
sulfation: phase I or II
II
effect of acetylation and methylation on drugs and what phase
makes them less water soluble and inactivates them
- phase 2
how do you eliminate protein bound drugs through renal system
NOT through filtration
–> active tubular secretion
excretion rate vs clearance
excretion rate: mass eliminated
clearance: rate removed from plasma, mL/min (more important)
describe zero order kinetics
constant amount eliminated over time independent of the drug concentration
- ex: alcohol
how to administer drugs with long half lives (digoxin)
give a “loading dose” (high dosage) to get it going and then continue with maintenance doses
