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List the four basic pharmacokinetic processes.
- Absorption
- Distribution
- Metabolism
- Excretion
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What is the difference between enteral drug administration and parenteral administration?
Enteral administration is through the small intestine, such as taking a pill P.O. Parenteral is anything other than having the drug absorbed via the small intestine, such as getting a shot.
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What are some factors that affect GI absorption related to absorptive surface area?
Interaction with other substances in gut like food, calcium, enzymes, acid, degree of blood flow = greater absorption Higher GI motility = Lower absorption (goes through faster, less time to absorb)
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Why could a person with pancreatitis have difficulty absorbing drugs?
Because the pancrease creates enzymes that assist with absorption.
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What are four factors that can affect GI absorption related to transport across membranes?
- Passive Diffusion: most common - from higher concentration to lower concentration
- Facilitated Diffusion: requires a transport protein, but NO energy
- Active Transport: requires a transport protein AND energy
- Filtration: gases and small ions forced through pores or channels in membrane along with water
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List four factors that affect GI absorption that are related to the drug.
- Ionization
- Lipid solubility
- Bioavailability
- Size/Formation
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Does ionization make the transfer across membranes faster or slower?
Slower
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Most drugs are strong/weak acids and bases?
Weak
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Weak acids ionize in what? What do weak bases ionize in?
Basic solutions / Acidic solutions
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If is drug is fat (lipid) soluble, does that make it easier or harder to absorb the drug across a membrane?
Easier (and faster)
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If a drug is water soluble, does that make it easier or harder to absorb that drug across a membrane?
Harder (and slower)
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If a drug is charged, does that make it harder or easier to absorb it across a membrane? What about if it is uncharged?
- Charged = harder
- Uncharged = easier
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Are hydrophilic drugs charged? Are lipophilic drugs charged?
No (hydro) / Yes (lipid)
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What is bioavailability?
Bioavailability is the proportion of the drug that passes into the systemic circulation after oral administration.
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How do you figure the bioavailability? What is the optimal number?
- Amount in circulation/Amount administered
- Optimal bioavailability number is 1.
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What is the First Pass Effect?
When oral drugs are absorbed from the GI tract, they go directly to the liver via the hepatic portal vein. Some drugs can be easily metabolized by the liver and therefore inactivated on its first pass through the liver and have no therapeutic effect. Nitroglycerin is an example, that is why it is given parenterally.
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What is the cell lining in the gut?
Epithelial
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What is the cell lining in the blood vessels?
Endothelial
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What drugs can use passive diffusion?
nonpolar, lipid soluble, low weight
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What types of drugs need active transport?
polar, ionized, large
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Rate of absorption =
Amount of absorption =
- When effects begin
- Intensity
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What is the overall goal/effect of Phase I biotransformation?
Catabolic (oxigenation, reduction, hydrolysis); makes drugs water soluble so they can be excreted by the kidneys.
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Does Phase I biotransformation activate or inactivate drugs? What about Phase II?
- Phase I - both
- Phase II - inactivates
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What does Phas II metabolism do?
Conjugates the metabolites created after phase I so they are polar, inactive particles.
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Do protein bound drugs filter at the glomerulus?
No
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What types of durgs experience passive tubular reabsorption back into the bloodstream?
Small, non-charged, lipid soluble
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What is the "clinical significance" in relation ot drug responses?
The concentration of the drug that is needed to produce a therapeutic effect.
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What is the MEC?
Minimual effective concentration. The lowest does of a drug that will produce an effect.
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Is a wide of narrow therapeutic index safer?
Wide
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How is the therapeutic index calculated?
Lethal Dose/Therapeutic dose
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What is the "steady state" adn how many 1/2 lives does it usually take to reach it?
The point at wich the dose is the same as the amount of the drug secreted. About 5 half lives.
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Which one of the following takes the longest for a reaction? Ligan-gated, intracellular receptors or enzyme-linked receptors?
Intracellular receptors
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The single occpancy theory states responses are proportional to the number of receptors occupied. Is that true?
No.
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What are the 2 aspects of the modified occupancy theory of drug pharmacodynamics?
- Affinity (potency; the key fits but does not turn)
- Intrinsic Activity (efficacy; the key fits and turns the lock)
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Describe an antagonist. What does it have and what does it not have?
Molecules that prevent receptor activation; they have affinity, but not intrinsic activity
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Describe a competative antagonist.
Binds reversably and completes with an agonist for receptors. They can win if the dose exceeds the agonist.
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Does Aspirin, a weak acid, get ionized in the stomach or the the urine? What effect does that have on reuptake?
Urine, since it is ionized in the urnie it does not get reabsorbed into the tubules.
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What is the bioavailablity of parenteral drugs?
100%
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A large volume distribution (Vd) requires a drug to have an increase/decrease half life
Increased
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A large Vd will cause the serum concentration to be high or low?
low
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How does protein binding affect drug distribution?
Drugs with increased protein binding = decreased Vd because only the unbound drug can get out of the vessels to the tissues.
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What is a 1/2 life?
The amount of time it takes for 50% of the drug to be excreted.
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How do most drugs leave the vascular system?
Pores in the capillary membrane.
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What is unique about the capillary membrane's junctions? Why is this important?
They are tight so drugs can't pass between them; need to be lipid soluble to pass through them.
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If you administer a drug that is 95% protein bound and one that is 98% protein bound which will have a bigger effect?
The one that is 95% protein bound because the 98% bound will knock it off leaving more free 95% in the circulation. This increases the effect of the 95%.
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Hhow can hypoabuminemia affect drug administration?
Not much protein to bind to = more free drug = greater effect
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Where does most drug metabolism take place?
Liver
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What are two phases on biotransformation (drug metabolism)?
- Phase I (catabolic)
- Phase II (anagolic)
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What is the hepatic drug metaolizing system called?
Cytochrome P450 system
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What is the effect of CYP21 and p450 enzymes inducers and inhibitiors in phase I of drug metabolism?
- Induces increase/promote metabolism
- Inhibitors decrease metabolism
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Describe type I drug reactions.
Dose related and predictable
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