Pharmacokinetics and drug formulations Flashcards
Pharmacokinetics definition
what the body does to the drug
pharmacodynamics
what the drug does to the body
what factors can decrease dissolution of a medication in the gut?
- hydrolysis: water destroys the molecule
2. the drug does not dissolve well in acid or the stomach is not acidiec enough
which equation describes the rate of dissolution?
the noyes-whithney equation
where is the major site of drug absorption?
the small intestine
in what PH do enteric formulations get absorbed
in basic environments like in the small intestine
why can AMG no be given PO?
they are polar charged molecules that cant pass through cell walls. The remain in blood more and thats one reason they are nephrotoxic
what are two of the most common protein-bound medications?
phenytoin and warfarin
when is elimination of a medication considered complete?
after 4-5 half lives
what is first order kinetics?
the amount of drug given is proportional to the increase seen in plasma concentration. The more you give of a drug, the higher the drug concentration
what is michaelis menten kinetics?
at first, an increase in drug is proportional to its concentration in the blood. That is until, the metabolizing enzymes become saturated. Then the elimination rate of the drugs becomes independent of the drug concentration: the amount can increase dramatically and lead to toxicty
what are three main examples of drugs that follow michaelis menten kinetics?
phenytoin
voriconazole
theophylline
what are good formulations for people who have trouble swallowing?
orally disintegrating tablets patches some bead formulations sprinkled onto food suppository IV
why are migraine medications in ODT form?
because migraines usually cause nausea and these meds can cause nausea when swallowed. So giving ODT reduces nausea
what formulations are better for patients that are non-adherent?
Long acting formulations
what is the main cause of side effects
when you get a quick peak vs a gradual rise in the concentration of the drug. This allows the drug to interacat with the wrong receptors, leadingto side effects.
which medications should not be crushed or chewed?
long-acting: XR, ER, LA, SR, CR,
CRT, SR, TR, TD, have 24 or end in -CONT Contin, or are sprinkles or timecaps
which XL formulation can be cut in half?
Toprolol XL
why does mesalamine come as a suppository?
because the diseases is found n the distal portion of the intestine: reduced SEs
can patches be cut? which are exceptions?
usually you cannot. Exception is lidoderm. YOu can cut it and put over the painful area
should patches be exposed to heat?
almost all cases no. Esp from a fever, an electric blanket or heating pad
what to do when a patch is bothering a persons skin?
- make sure they are changing where they apply the patch every time
- dont shave before hand in that area
- Can apply hydrocortisone OTC (if the skin is already irritated from being w/ a patch on )
common patches that need to removed before MRI
nicotine testosterone fentanyl clonidine and more
what to do about problems with sticking and unsticking?
- do not cover it with tape in most cases
- they dont stick to lubricated skin
- make sure to press down for the adequate amount of time
- does not stick to hairy skin. Shave in advance or cut hair close to skin, or use a non hairy site
how freqently to put on fentanyl patch
q 72h
how freqently to put on nicotinel patch
every day
how freqently to put on lidoderm patch
1-3 patches on for 12 hours, then off for 12 hours
where is the transdermal scopolamine patch placed?
behind the ear, alternating ears
where to place estrogen patches:
mostly lower abdomen, some upper buttock. Never breasts
where to place topical pain patches:
over painful areas except for opiods which work systemically
how to discard patches
fold patch, pressing adhesives together and discard
fentanyl can be folded and flushed. Or ti can be cut up and mixed wit/ noxious substances and then thrown in the trash
Can also flush buprenorphine
