principles of drug action Flashcards
what is the objective of drug therapy
provide max benefit with min harm
t/f: drug response determined by interaction within the body
true
what charge should most drugs have to be to go into a cell
neutral charge
ways that drugs can cross cell membrane (3)
- between spaces or channels
- transport system (p-glycoprotein)
- penetrate membrane directly (most drugs)
job of p-glycoprotein
protein that helps transport drug out of cell for elimination
p-glycoprotein and the liver?
transport drugs into bile for excretion
p-glycoprotein and the kidneys?
transports drugs into urine for elimination
p-glycoprotein and the placenta?
transports drugs back into maternal blood
p-glycoprotein and the brain?
transports drugs circulating blood to limit access to the brain
pharmacokinetics
study of drug movement throughout the body
absorption
movement of a drug from its site of administration into the blood
bioavailability
fraction of a drug that is absorbed into the circulation after administration
- can be different b/w generic + trade
explain how to determine bioavailability between IV and PO dose
at home –> PO levothyroxine 100mg
bioavailability IV = 1 and PO = 0.5
how much should the pt take IV at hosp?
pt had PO levothyroxine (Cynthroid) 100mg
–> routes always compared to IV
if IV ba = 1 and 100mg and PO = 0.5
then IV dose should be 50 mg
what are 6 factors that can affect absorption?
- solubility
- surface area
- ionization
- blood flow
- GI motility
- drug-drug/drug-food interactions
distribution
how drug molecule in bloodstream finds target receptor and into cells
what are 3 factors that can affect distribution?
- blood flow to tissues
- ability to leave blood
- ability to enter cells
what is tissue binding
some drugs = high affinity for specific tissues in body –> bind to tissue inappropriately –> attaches, no distribution
placental distribution vs BBB
opposite; drugs can easily pass through in the placenta, putting fetus at risk for whatever substances the mother is taking
protein binding
when drug is bound to protein = CAN’T pass through capillary walls (drug can’t do its job until unbound to protein)
- ex football player and cheerleader
high protein bound drug
- do you need higher or lower dose and why?
high affinity to protein, need HIGHER dose so that some drug molecules will able to distribute
low protein bound drug
low affinity to protein, do not necessarily need a higher dose since lower chance for the molecule to attach to protein
biotransformation/metabolism
- what chemical change occurs
how the body takes the drug molecule and transforms it into a different substance
lipophilic –> hydrophilic for excretions
does biotransformation always result in a smaller molecule?
naur
where are most drugs metabolized
liver