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This study focuses on what the body does to drugs after they are administered.
Pharmacokinetics
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What are the four stages of pharmokinetics?
Absorption, distribution, metabolism, excretion
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High to low concentration
Simple diffusion
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Moves along the concentration gradient utilizing a carrier protein. Does not use energy
Facilitated diffusion
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Movement against a gradient and requires energy.
Active transport
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stage of pharmacokinetics that involves movement of the drug form the site of administration to the bloodstream
Absorption
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For a factor affecting absorption, the higher the dose, the __ concentration gradient for diffusion? (pg 44)
greater
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For oral meds, most absorption occurs where?
in the small intestine
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What do high fat foods do to med absorption?
they slow the process down
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How does blood flow affect absorption?
Areas of high blood flow (large muscles) that have a high blood supply will have faster absorption and vice versa
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Acids are absorbed in __ because they are nonionized
Acids. Ex) asprin absorbed in the stomach (acidic environment)
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Bases are absorbed in __ because they are nonionized.
Bases. Drugs that are weakly basic are better absorbed in alkaline environments such as the sm intestine.
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the greater the surface area, the __absorbtion will be.
Faster. ex) lungs, sm intestine.
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The second stage of pharmokinetics that transports drugs throughout the body via blood stream
Distribution
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organs such as the heart, liver, kidneys have a higher exposure to a distributed drug because why?
They have a greater blood supply.
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__ soluble medications can cross barriers such as the blood/brain barrier wich make them have a wider dristribution.
Lipid
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tissues such as eyes, bone marrow, teeth and adipose tissue can store __ amounts of protein affecting distribution.
high
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Drugs often bind to protein and form drug-protein complexes making them not able to cross cappillary membranes (trapped. only __ drugs will reach target cells?
unbound
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Drugs often __ with one another for protein sites causing intercations affecting distribution.
Compete
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Drugs compete for protein sites with other drugs that can cause displacement. Why is this dangerous?
Displaced meds can reach high levels of free medicatino which can cause adverse effects.
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The blood brain barrier affects distribution because drugs cannot pass through it with the exception of what kinkd of drugs?
Lipid soluble.
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What can inflammation do to permeability?
increase it.
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3rd process of of pharmokinetics that the body uses to chemically change a drug molecule also called biotransformation.
Metabolism.
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Where is the primary site for durg metabolism
The liver
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Chemical changes always result in what?
Functional changes
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Changes in the drug structure allow for what?
allow for excretion. Lipid sluble to water soluble
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What are the products of drug metabolism?
Metabolites. Usually less active than the original molecule but they may be more toxic. ex) Tylenols metabolite is highly toxic to the liver.
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Medications that have no pharmacologic activity until they undergo metabolism.
Prodrugs
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Metabolism takes place in the liver throught hte the hepatic microsomal system aslo known as?
P-450 system. Its has more than 50 CYPs (enzymes that metabolizes drugs. Different CYPs are called isozymes.
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Not only do CYPs determine the speed at which a drug is metabolized, they also contribute largely to what?
Drug-drug interactions.
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Besides the liver, where also can drug metabolism occur?
the kidneys and small intestine.
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Drugs metabolized by a CYP enzyme.
substrate
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A drug that inhibits or stops the action of the CYP isozymes which increases toxicicity. Can contribute to toxic drug levels.
Inhibitors
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Drugs that accelerates metabolism of specific isozymes. These may cause drug level to drcrease more rapidly.
Inducers. With these you may need higher dosages for a theraputic effect.
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Drugs absorbed after oral administration cross directly into the hepatic- portal circulation which carries blood to the liver before it is distributed to the to other body tissues. What is this called.?
The first pass effect.
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Why do drugs need with a high first pass effect need to be administered by another route other than oral to be effective?
because some drugs get completely metabolized which losing their effectiveness.
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In older people Enzyme activity is often __?
reduced.
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With liver impairment, a person will have decreased __?
drug metabolism.
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regarding infants, how is metabolism affected?
infants lack mature microsomal enzyme systems.
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