pharmacology principles Flashcards
the ideal drug
effective, safe, selective, provided max benefit with minimal harm, reversible, predictable, easy to administer, free from drug interaction, low cost, chemically stable, with simple generic name
what do drugs do
modify existing functions within the body
determination of drug reponse
how drugs interact with in the body
solubility
how well an amount of a given substance will dissolve in liquid
for a drug, needs to be lipophilic to dissolve in stomach/gi tract
ionization
process where a molecule is given an electrical charge
effects how easily a drug can go through cell membranes and bind to receptors
affinity
the attraction of a drug to the receptor
high affinity
drug molecules bind to receptors at low drug concentrations
low affinity
drug molecules bind to receptors at higher drug concentrations
no affinity
no drug molecules bind to receptors
how do molecules cross cel membranes
passing between molecules through spaces/ channels
with help of transport system
pentrate membran directly
P-glycoprotein
moves drugs out of cells and into the liver for bile elimination, kidneys for urine excretion, , placenta for back int maternal blood, into blood to limit brain access
how do most drugs go through membranes
penetrating directly, they are too big to go through channels and lack transport systems
absorption
movement of a drug from its site of administration into the blood
rate of absorption
how soon effects will begin
amount of absorption
how intense the effect will be
where are po med absorbed
the small intestine because of its large surface area
bioavailability
the fraction of a drug that is absorbed into the circulation post administration
bioavailability scale
1- all of given drug is available in blood stream (like with IV)
0- none is available
what can effect absorption
solubility, surface area, ionization, blood flow, gi motility, drug/drug/food interaction
how can gi motility effect absorption
if it is too fast, absorption may be lower as it does not spend enough time in the small intestine
Distribution
movement of a drug through blood stream, into tissues and eventually into cells
what does distribution depend on
blood flow to tissue
drug ability to leave blood
drug ability to enter cells
how can blood flow affect ditribution
impeded by areas with low regional blood flow, like tumors, abscesses, or scar tissue
how can protein affect distribution
slows distribution, will stay in body longer with more protein
protein binding
drugs binding to protein, making them unable to pass through capillary walls
low protein on distribution
if someone has low protein in their body/is malnourished, they may become toxic as the active drug will be in their system more
ex. liver failure
high protein binding
lots of binding to drugs
blood brain barrier impeding distribution
protects brain, only lipi soluble and transport system drugs can pass tight junction
not fully developed at birth- higher sensitivity to CNS drugs
low protein bound
little binding to drugs
placenta membrane in distribution
lipid soluble, nonionized compounds easily pass
meds affecting pregnant person will also effect fetus
Metabolism
biotransformation, conversion of drug from one substance to another
typical metabolism changes
lipophilic to hydrophilic, active to inactive
where does metabolism primarily occur
mainly liver, also GI, kidney, lungs, brain ,skin
metabolite
typically toxic product of metabolism
prodrugs
drugs converted by metabolism from inactive to active from
hit liver, activate, enter blood stream
first pass effect
liver metabolizes drug and it then returns to systemic circulation, decreasing the mout of drug acting on intended site
little to no efffect until they take it again
what can effect drug metabolism
babies/elderly woth lower metabolism, drug competition, enzymes, prgnancy, liver disease, nutritional status
P-450 system
liver metabolising via cytochrom system liver enzymes
CYP3A4
common enzyme responsible for metabolsim of most drugs
drug substrates
drugs metabolized by a CYP enzyme
drug enzymer inhibitors
inhibit action of CYP isoenzymes, whic hcan cause toxic drug levels
enzyme inducers
accelerate metabolism of specfic isoenzyme cause rapid drug level decreases
excretion
removal of drug from the body
typical route of excretion
urine, also bile, expired air, breast milk, sweat, saliva
bile excretion
bile circulated back to the liver may stay in system and increase 1/2 life and duration of drug
what can effect excretion
renal function, ph-dependent ionization, ege
Absrption in the elderly
intestinal motility, gastric production, intestinal blood flow, number of absorption sites decrease
gastric ph increases
distribution in the elderly
percent body water, lead body tissue, protein binding sites, serum albumin decrease
percent fat tissue, amount of free drug, drug toxicity increase
elderly metabolism
liver mass/function, hepatic blood flow, first pass effect increase
elderly excretion
renal function, glomerular filtration rate, renal blood flow, tubular secretion, creatine clearance decrease
pediatric absorption
In prematrue infants: increased gastric pH, slower gastric emptying, increased permeability of gastric mucosa
may not be a throughouly absorbed
pediatric distribution
higher percent of body water in newborns, requires higher amounts of drug
pediatric metabolism
decreased liver metabolism in newborns, exceeds adults in around 4 yrs old, decreases in adolscence, adult level reached by late puberty
pediatric excretion
renal elimination decreased in newborns, adulte rate by 2 years ol
pediatric plasma protein bonding
decreased plasma protein binding, so increased sensitivity to protein bound drugs
pediatric drug doses
dosed by body weight or age, adjusted based on drug levels, increased loading dose, lower maintenance dose
renal diseases and drugs
increased creatine levels- decreased absorption because of nausea/vomiting
decreased absorption from GI tract edema
decreased protein binding
increased total body water- decreased tissue binding
decreased liver metabolism,- metabolites accumulate
because less excretion, lower doses
Lower absorption, but what is absorbed can cause toxicity because of lower protein binding, and less excretion
Hepatic disease and drugs
decreased metabolism, causes increased drug levels
lower albumin production, causes increased free drug
lower liver blood flow, decreased drug clearance
increased interstitial fluid, increased volume of distribution
easier chances of toxicity because drug remain in body, will not get inactivated by liver
Pregnancy and drugs
most drugs will easily pass into the placenta, renal blood flow increases, will excrete drugs faster, decreased gstric motility- more absorption
pharmacodynamics
action of a particular drug within the body and the study of how the actions occr
drug action
interaction between drug and cellular components
drug effect
persons response to drugs action
Drug-receptor interactions
drug attach to receptors, are able to stimulate or block that receptor
Agonists
drugs molecules attach to a receptor and stimulate cell to act
function promoting
partial agonists
allows half of what a cell can doll
full agonists
100% response effect of cell
Antagonists
blockers- attach to receptor and prevent attachment and effect
competitive drugs
drug with highest affinity will attach first
Duration
length of stay in therapeutic range
Half-life
the amount of time it takes to remove 50% of the blood concentration of a drug
determines dosing
steady state or plateu
when amount eliminated and amount being administered are equal
this is when pharmacotheraputic response is measured
How long does it take ro reach steady-state
around 4-5 half lives, an increase in dose will not make it happen faster
maintenance dose
daily dose
loading dose
larger dose for quicker therapeutic effect
blood concentration
determines if dose is in correct range, clsoely monitored
potency
amount of drug needed to produce a particular response
efficacy
how well a drug produces desired effect
adverse response
any unexpected or unintended response to a drug
side effect
unavoidable secondary drug effect produced at therapeutic doses
predictable adverse responses
side effects, toxic effects, cumulative effects
cumulatiev effects
rate of administration exceeding rate of biotransformation or elimination
unpredictable responses
idiosyncratic, iatrogenic, allergic, anaphylactic
drug-drug interactions
change in response of one drug in resposne to presscence of another drug
additve drug effects
1(drug 1) +1(drug 2)= 2
synergistt drug effect
1 (drug1) +1(drug 2)= 3
potentiation drug interaction
1/2 (drug1) + 1(drug2)= 2
antagonsim drug interaction
1(drug1) + 1(drug2)=0
grape fruit
can inhibit metabolism of certain drugs
