Pharmokinetics Flashcards
Pharmacokinetics
how medications travel through the body
Medications biochemical processes:
absorption, distribution, metabolism, and excretion
medication absorbs through what?
the bloodstream
Oral Barriers to Absorption
Medications must pass through the layer of epithelial cells that line the GI tract
Absorption Pattern varies greatly due to:
- Stability and solubility of the medication
- Gastrointestinal pH and emptying time
- Presence of food in the stomach or intestines
- Concurrent medications
- Forms of medications (enteric-coated pills, liquids)
Sublingual
under the tongue
Buccal
against the mucous membranes of the cheek
do Subcutaneous and intramuscular have Barriers to Absorption? if so why or why not?
no barrier because there’s huge spaces between the cells capillary walls.
how long does it take Highly soluble medications to absorb?
rapidly.. 10 to 30 min
Poorly soluble medications
have slow absorption
Sites with high blood perfusion absorbs fast or slow?
fast absorption
sites with low blood perfusion absorbs slow or fast?
slow absorption
does the Intravenous route have barriers to absorption?
what does intravenous immediate mean?
what does intravenous complete means?
-no barriers
-medication enters directly into the blood
-medication reaches the blood in its entirety
Circulation
Conditions that inhibit blood flow or perfusion (peripheral vascular or cardiac disease) can delay medication distribution
Permeability of the cell membrane means what?
-must be able to pass through tissues and membranes to reach its target area.
*Medications that are lipid-soluble or have a transport system can cross the blood-brain barrier and the placenta.
Plasma protein binding
Medications compete for protein binding sites within the bloodstream, primarily albumin. The ability of a medication to bind to a protein can affect how much of the medication will leave and travel to target tissues. Two medications can compete for the same binding sites, resulting in toxicity.
Metabolism (biotransformation)
-transforms medications to not work as much or not at all with the help of enzymes.
This occurs primarily in the liver, but also takes place in the kidneys, lungs, intestines, and blood
True or False. Hepatic (liver) medication metabolism tends to decline with age
True, older adults require smaller doses of medications due to the possibility of accumulation in the body
What happens with an increase in some medication-metabolizing enzymes?
This can metabolize a particular medication sooner, requiring an increase in the dosage of that medication to maintain a therapeutic level
First pass effect
the liver inactivates some medications in their first pass through the liver.
-thus, they require a nonenteral route (sublingual, IV)
What happens when medications have similar metabolic pathways?
When the same pathway metabolizes two medications, it can alter the metabolism of one or both
-the rate of metabolism can decrease for one or both leading to medicatiion accumulation
Excretion
the elimination of medications from the body, primarily through the kidneys
Where can elimination take place from the body?
kidneys, liver, lungs, intestines, exocrine glands (breast milk)
Kidney dysfunction can lead to?
an increase in the duration and intensity of the medication’s response, which can lead to toxicity
Whats a plasma medication level?
the therapeutic range when its effective and not toxic
therapeutic index (TI)
the ratio of the medication’s lethal dose to its average effective dose
Do medications with a low TI require close monitoring?
yes
Do medications with a high TI require close monitoring?
no
half life
time for the med level to drop by 50%
what parts of the body affects half life?
liver and kidney
agonist
activates receptors
antagonist
blocks receptors
receptors
the medications target sites on or within the cells
partial agonist
acts as agonist and antagonist
transdermal
medicated skin patch
true or false
The client should sit upright or lie supine to instill eye meds
true
true or false
client should tilt their head slightly and look up at the ceiling to instill eyedrops
true
