NCC content Flashcards
(66 cards)
define pharmacodynamics
the ACTION part
“what the drug does to the body”
-the activity of the drug at the tissue receptor site; the free drug binds to a specific receptor site causing a desired response
define pharmacokinetics
the MOVEMENT part
“what happens to the drug once it enters the body”
-movement of a drug in, through, and out of the body
what are the four parameters of pharmacokinetics?
ADME
- absorption
- distribution
- metabolism
- excretion
what is active transport?
requires energy in order to move substance into intracellular space through pump (against concentration gradient)
what is facilitated diffusion?
when a substance needs an accessory protein to carry it through the cell membrane (follows concentration gradient)
define bioavailability
amount of drug dose that reaches systemic circulation
-IV route is 100% bioavailable
what is first pass metabolism?
when an organ (i.e. liver) utilizes a portion of the drug before it gets to the bloodstream
Why is absorption delayed via the PO route?
- delayed gastric emptying
- stomach pH is more neutral (7-8) until 2-3 months of age
- NPO status
- increased transit time
which environment provides best absorption for acidic drugs?
an acidic environment
why is absorption increased via the topical route?
- higher surface area to body weight
- increased permeability of skin
- decreased stratum corneum
define distribution
transport of the drug from the bloodstream to the site of action
define absorption
getting the drug from the site of administration into the blood circulation
how does circulation affect distribution of a drug?
increased blood flow = increased drug delivery to tissue
-rate of blood flow to tissue
how does total body water content affect distribution?
increased total body water = more drug needed
-Vd = volume of distribution
how does protein binding affect distribution?
increased protein binding = less free drug available
-too much protein binding prevents a drug from having the ability to reach the tissue/receptor site
how does lipid solubility of a drug affect distribution?
lipid soluble drugs move better across membranes
how does tissue receptor affinity affect distribution?
increased affinity = increased delivery of drug to site
what are the 3 actions of metabolism?
- biotransformation: the drug is chemically altered to an inactive form
- changed to a water soluble drug (to be excreted through kidneys)
- changed into an active metabolite
where does the majority of metabolism take place?
in the liver
cytochrome P450
why are preemies at higher risk for drug toxicity?
- immature liver function for metabolism
- decreased protein = more active free drug
- immature renal function = cannot eliminate drugs as well; GFR is decreased, tubular function is decreased
why factors decrease drug metabolism in preemies?
- prematurity
- decreased cardiac output
- renal insufficiency
what is 1st order elimination?
- a constant fraction of drug is eliminated over time
- proportional to amount given
how many half lives does it take for an entire drug to be eliminated?
5 1/2 half lives
how many half lives does it take to reach steady state?
5 1/2 half lives
