pharmacokinetics I- drug administration, absortion, and distribution Flashcards
two primary routes of administration
alimentary canal to enteral administration
non-alimentary routes to paraenteral administration
enteral routes
oral and rectal
What is the most common method of enteral medications
oral
oral advantages
easy , safe, convenient
oral disadvantages
limited absorption of some drugs
change of first pass inactivation in liver
most oral medication is absorbed from
the small intestine
define first pass effect
drugs is transported into the liver via the portal vine where a large amount of the drug may be metabolized and destroyed prior to reaching the target tissue
sublingual drugs
are placed under the tongue
buccal drug
the drug is placed between the check and the gums
do the sublingual or buccal go thru first pass effect?
none
rectal drugs
via the rectum
rectal advantages
local effect on rectal tissues
rectal disadvantages
poor or incomplete absorption
parental routes
inhalation
injection
topical
trasndermal
parenteral
drug administration that does not us the Gi tract
delivers more directly to the target site
more predictable drug quantity
parenteral inhalation advantages
rapid onset
direct application fro respiratory disorders
large surface area for absorption
inhalation disadvantages
chance of tissue irriatation
parenteral injections advantages
provided more direct administration to target tissues
fast
injection disadvantages
chance of infraction is sterility is not maintained
intro arterial injection
directly into an artery
subcutaneous injection
injecting medications directly beneath the skin for locate response
the SC route can also be used when a drug needs
it be slowly dispersed from the injection site and absorbed into the bloodstream for several weeks or months
intramuscular injection
easily accessible
steady, prolonged release
repaid effect
iontophoresis and photophoresis
use the transdermal route
iontophoresis
electric current driver th ionized for of medication thru the skin
phonophoresis
uses ultrasound waves to enhance transmission of medication thru the dermis
define bioavailability
the extent to which the drug reaches the systemic circulation
bioavailability depends on
the route of administration and the drugs ability to cross membrane barriers
the cell membrane is so posed primarily of
lipids and proteins
membrane lipids are..
phospholipids which are composed of polar, hydrophilic head and a lipid , hydrophobic tail
membrane proteins exist where
in the outer or inner portion of the methane
lipid soluble compounds..
are able to pass directly thru the membrane by dissolving in the lipid bilayer
the ability of a substance to pass thru a specific pore depends on
the size, shape and electrical charge of molecule
passive diffusion
does no use energy
charged particles , chemical, and pressure difference on the 2 sides of the membrane
the rate of passive diffusion depends on
the magnitude of the gradient, size of substance, distance and temp
the second essential factor for passive diffusion to occur is that
the membrane must be permeable to the diffusion substances
many drug are ..
lipid soluble
drugs will diffuse more easily thru the lipid belayer if they are
non-ionized
ionization decreases their lipid solubility
ph 1-3
acidic
ph 5-7
neutral
ph 7-8
base
When a weak acid drug is in an acidic environment it tends to be
in its neutral, no ionized form
when a weak base is ionized in the acidic environment once it reaches the duodenum
is become nonionized and lipid soluble allowing it to be absorbed from the proximal small intestine
diffusion trapping
wants the drug to be ionized in the urine or the body can get rid of the drug, by if it becomes nonionized while in the nephron it may be reabsorebed
if the urine is basic
weka acids drugs are trapped in the nephron and get ride of fast
if the urine is acidic
weak bases are excreted better
diffusion between cell junctions
primary way that a drug may diffuse across the barrier by first into and then out of the other side
define osmosis
refers to win the diffusing substance is water
when osmosis happens ..
the water moves from an area where it si highly concentrated to an area of low concentration
active transport
use membrane proteins to transport substances across the cell membrane
does active transport need energy?
yes
characteristics of active transport
carrier specificity
expenditure of energy (ATP hydrolysis)
can transport substances against a concentration gradient
define facilitated diffusion
has features of both active transport and passive diffusion
assist in protein carrier but no net energy
best example of facilitated diffusion
glucose into the skeletal muscle cells
endocytosis
transport substances across their membranes
exocytosis
substances synthesized within the cell can be encapsulated in vesicles and put out of the cell
factors affection distribution
tissue permeability
blood flow
binding to plasma proteins
binding to sub cellular components
volume of distribution
if the number is high than the volume in ur blood is high and not in the tissue
drugs storage sites
adipose
bone
muscle
organs
primary organs for drug storage
liver and kidneys
what is the primary site for drug storage
adipose tissue bc a lot of lipids and many drugs are lipid soluable
adverse consequences of drug storage
high concentration of drugs within the tissue can cause local damage to liver and kidneys
drug storage occurs when a reservoir
soaks up the drug and prevents in from reaching the target site
nanotechnology
involves the use of very small particles with physical properties that help drug absorption within the body
is volume distribution is less than the total body fluid content then..
the drug is retainined in the blood stream due to factors such as plasma protein binding
if volume distribution is high than the total body fluid then..
it indicated that the drug is being concentrated in the tissues
