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therapeutic factors taht affect the administration of a drug:
onset of action
site of action
adv: safe, economical, noninfectious
dis adv: inactivation, palatability, slow onset
adv: rapid onset, duration of action is longer than IV
disadv: can cause tissue damage
the optimal dose, which lies between the maximal and minimal doses. has a desirabel effect
the amount that produces undesirable clinical, hematological, biochemical or pathological alterations
Standard safety margin
ssfactor = Ld1/Ed99
ld1-ed99/ed99 x 100 is a percent that is more accurate then TI
an enzyme tha tis used for conjugation. NOT IN CATS!!! will help to metablize salicylate (asprin).
the half life of asprin in cats will _______ due to little of what enzyme?
increase, glucuronyl transferase
asprin use in dogs....
will cause an inflammatory reaction due to the convertion of arachadonic acid to leukotrienes instead of PGs
single nucletotid polymorphisms. in less than 1% of the population. no necessarily in a gene,and do not alwyas affect protein functions
noncoding causative SNP
located in the gene regulatory sequence changes the level of gene expression.
what do the young and the old have in common?
-decrease ability to biotransform
-decrease drug excretion
-decrease protein binding
NSAID effect on a nomral patient
will decrease COX-2 = decrease inflammation
decrease COX1 = decrease vasodilation = decrease bld flow to kidney
NSAID effect on hypotenion patient
total lack of blood flow to the kidney. can lead to renal failure
genetically determined unpredictable abnormal reaction to drugs.
fever, uticaria, anaphylaxis
resistance to ordinary dose of a drug. decrease responsivness to repeated doses of same or similar drug
occurs following concurrent or sequential administration of drugs.
can be summative, synergistic, additive, or antagonistic.
can be beneficial or toxic
factors that affect absorption related ot the drug:
degree of ionization
dissolution in water
concentration at the site
route of administration
how does molecular size affect absorption?
small = fast absorption, aqueous diffusion or thoruhg a lipid channel
large = absorption is lower via facilitated diffusion or endocytosis
how does lipid solubility affect absorption?
increase lipid content = increase diffusion
increase water solubility= decrease diffusion`
how does ionization affect absorption?
nonionized drugs are more important for passive diffusion
increase NI/I ratio and increase diffusion
how does dissoluiton in water affect absorption?
-oral absorption of a liquid is faster than a solid
how does concentration at a site affect absorption?
- high concentration will increase absorption rate.
how does route of administration affect absorption rate?
oral is slower than injection
factors that affect absorption related to the drug
-absoring surface area
how does blood flow affect absorption?
increase blood flow = increase absorption
bld flow can be modified by heat, massage, other drugs, sympathetic NS, and edema
how does the absorbing surface area affect absoritong?
increase surface area = increase absorption
upper part of the SI is the best area for this
first pass effect
drug biotransforamtion that will reduce the quantity of drug that reaches circulation.
-per os administration
-occurs due to gastric enzymes
what affects distribution ofa drug?
make up of the drug
the formation of a substance is equal to its removal.
affected by area, permability, membranes, bld flow and concentration
bound drugs are inactive and are unable to be filtere, metabolized, or distributed.
-reversible, pro-longs half-life
-keeps the drug high in the plasma low in the tissue.
mostly bind to albumin
what affect does liver failure have on protein binding?!
protein bidning will be decreasebecause the liver amkes the palsma proteins
tissue binding consequences:
may increase the concentration of a drug in a tissue
drug is pulled outof the plasma
the tissue will hold onto the drug which will increase the time the drug is in the body
the study of the movment of drugs across biological memrbanes form the time of absorption until elmination
specific type of endocytosis in which the cell engulfs the molecule of drug.
often receptor mediated
no electrochemical gradient
one compartment model
all tissues and organs which the drug penetrates behaves as if they were already in equilibrium with the blood
1st order kinetics
the rate of removal of a drug from the plasma is proportional to the concentration at a given time
chemical alteration of the drug molecule in the body which will change the physicochemical properties of the drug and its pharmacological activity
consequences of the P450 system
turns drug into a more water soluble form
can cause the amking of toxic or nontoxic intermdiates
consequences of phase I reactions:
may "flag" the drug for furthe reactions
make active or inactivate the drug
may increase or decrease water solubility
may change drug strcture
conjugation can occur with:
glucuronic acid---most common!
increase bld flow to the kidney = increase filtered volume
affected by milecular size and filter rate
not affect by ionization
slow compared to tubular secretion
can move against concentration gradient
NOT affect by plasma protein binding
is important for nonionized lipophilic molecules.
affected by Urine pH and glomerular filtration
how is reabsorption afect by urine pH?
change the pH will cause drug trapping and increase elmination of the drug.
how is reabsorption affected by glomarular filtration?
fluid therapy and diruteics will increase renal excretion and decrease tubular reabsorption
highly lipid soluble = metabolized first
drugs can go to teh heptic cells or the bile
T or F? If there are drugs in the feces this means that there is still a chance for hte drugs to be reabsorbed?
cell constituents that bind to an agnoist with increase affinity and trigger a cell repsonse.
most are on the cell memrbane
example of upregulation:
hyperthyroidism in cats---will cause tachycardia tdue to an increasein teh B1 receptors
drug taht binds to a spontaneousy activated cell receptor to turn it off.
acts like an antagonist
binds to the receptor reversibly to prevent the agonist from binding
prevents the agonist from having an effect at any concentration due to its irreversible binding
when the drug has an agonist effect onn one receptors and an antagonistic effect on another type
ceiling, plateau, efficacy.
more important than potency.
higher the curve higher the efficacy
measured in Kd
variability in the response due to administration of the same drug does in an individual or group
variabilty in the response in the dose requried to see a measureable effect (X axis)
the smaller the dose needed to produce an effect the greater the potency
related ot the concnetration that produces Emax
can be obtained form a graded or quntal curve
the slope of the curve indicates the range of doses over which the drug acts.
shallow slope = decreased toxicity
increased slope = increased toxicity
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