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49 Cards in this Set

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Are the following attributes of pharmaco kinetics or dynamics? Therapeutic effect and toxic effect
dynamic
Are the following attributes of pharmaco kinetics or dynamics? Absorption, distribution, metabolism and excretion
kinetic
What are the two options for a drug to move from the blood to many tissues?
through the cell or around it
What determines drug transport through a lipid bilayer via passive diffusion? Is carrier-mediated transport active or passive?
(1) concentration gradient… (2) can be either
In passive diffusion across capillary endothelial membranes, which is the major factor determining diffusion? Capillary wall restraint or blood flow?
blood flow
Which two transport system are seen in Carrier-mediated transport?
active transport and facilitated transport
Can facilitated diffusion move againt a concentration gradient?
no
Which transport mediated transport includes these characteristics? Competitive inhibition, saturability, selectivity.
both active transport and facilitated transport
Which transport mediated transport includes these characteristics? seen in renal tube, neuronal membranes, choroid plexus and hepatocytes?
active transport
How do most drugs enter cells?
passive diffusion through the lipid bilayer
a) Show Flick's equation. b) Flick's law show that flux (passive movement) is dependent on which variables? b) What variable is not mentioned here but plays a big part in passive transport across a lipid bilayer?
a) Flux = (C1-C2 X area X permeability coefficient) ÷ thickness… b) [drug] across membrane (C1-C2) and lipid solubility (permeability coefficient)… b) not addressed in Flick's law is the pH along the membrane and drug pka, but they play a big role in passive diffuse
What are the 6 factors that determine absorption?
solubility, rate of dissolution, concentration at site, blood circulation at site, area of absorbing surface, route of administration.
For oral administration, what type of drug do you want lipid or aqueous soluble?
it's a balance, since it must be lipid soluble to pass through the membrane, however, if its too lipid soluble it will be unstable in the aqueous environment in the intestine and therefore be unstable and eratically absorbed.
Besides Flick's law and pH an pka, what other factors are important in absorption of an orally administerd drug?
Intestinal blood flow and gastric emptying (food mental state, diseases, other drugs, and endocrine status)
What does "extraction ratio" (a.k.a., Intrinsic clearance) mean?
the extent of removal of a drug form the circulation by the liver
What is the difference between "high" and "low" extraction drugs?
High Extraction = drug extensively removed by the liver… Low Extraction: little drug removal by the liver
Which type of drug is more sensitive to hepatic blood flow? High extraction or Low extraction
High, where high extraction drugs have extensive removal of the drug by the liver. Thus, in high hepatic blood flow there will be greater extraction and vice versa… (the opposite is true of low extraction)
What are two things that can decrease the first pass effect on high extraction drugs?
aging and liver disease
T/F sublingual administration bypasses the first pass effect.
TRUE
T/F Rectal administration of drugs is 100% absorbed into the system circulation
False, it is subject it can be subject to less first pass since there is less blood floow… but some drugs do bypass first pass by this method
Why are gaseous and volitale drugs ideal for rapid absorption through the pulmonary administration?
they are lipid soluble, small molecular size and vast aveolar area
Transdermal administration allows for slow and even absorption, what is the advantage of transdermal administration of drugs?
compliance, risk of injection, no variability seen in oral administration, better control of drugs with short half-lives.
When does the half-life start for transdermal administration?
at absorption
What are the requirements for transdermal drugs?
requirements: both lipid and water soluble
Which types (targets) of drugs are used in transdermal administration? Why?
cardiac, CNS and endocrine drugs… because of their slow and sustained release
What limits absorption of hydrophilic drugs via transdermal administration?
Stratum Corneum
List 6 advantages of transdermal administration.
1. Sustained release --> Stable blood levels… 2. Avoid first pass (no hepatotoxic effects)… 3. Pt compliance… 4. No injection risks… 5. No variability as seen in oral absorption… 6. Better control of drugs with short half-lives.
List 3 Disadvantages of transdermal administration.
1. Too slow for therapeutic efficacy of some drugs… 2. Toxicity and disease to skin… 3. Metabolism by skin
What is the criteria for transdermal drugs? (hint: potency, lipid soluble, water soluble, irritating, stability)
high potency, lipid sol to penetrate skin, water sol to enter systemic circulation, non-irritating to skin, stable in reservoir.
What percentage of IV drugs enter the liver during one circulation time?
30%, vs. 100% for orally administered drugs
What type of absorption is seen in IV drugs?
none… it's directly in to the systemic circulation
What are two of the dangers of IV administration of drugs?
overdose and toxicity
What are two of the advantages of IV administration of drugs?
rapid access to systemic circulation and accuracy in dosage
What factors determine the aborption of intramuscular and subcutaneous administration of drugs? Which type of drug would be a good candidate for subcutaneous injection?
lipid solubility and blood flow at site… (2) weak soluble, slow release form of a drug when slow long action is required, e.g., steroids
What are the disadvantages of transdermal administration?
penetration is too slow for therapeuitc efficacy of some drugs, toxicity and dz of the skin, drug is metabolized by the skin
What is the definition of bioavailability?
1. the % of drug that enters the systemic circulation after first pass… 2. Relative amount received in the systemic circulation from different modes of administration (other than IV)
a) What is represented in AUC (area under the curve)? (hint: Y/X coordinates)... b) What does the AUC reflect? c) What is the AUC used for?
a) plama levels/time… b) it reflects total amount of drug entering the plasma (systemic circulation)… c) calculate bioavailability (comparing different modes of administration)
Define Pharmaceutical equivalence
Drug content identical, but inactive ingredience and manufacturing may not be the same.
Define biological equivalence
provides the same [drug] to blood and tissues
Define therapeutic equivalence
provides equal therapeutic benefit
In which types of drugs is bioavailability a big factor?
drugs with a narrow therapeutic index
What does bioavailability measured by AUC NOT reflect?
rate of absorption… thus even though a rapid absorption demonstrates a peak [plasma] faster a slower performing drug can still have the same AUC
Does a "true" equivalent have the same rate of absorption? Are generic drugs necessarily equal in terms of bioavailability? What has the FDA done about BA?
a) yes, they would be the same in all respects… b) no, generic drugs can differ with respect to BA… c) requires that all new generic drug have equal BA
What is the FDA tolerance for a drug to be considered BA (AUC) and peak [plasma]? (hint: first order and zero order drugs)
The FDA requires (+/-) 20% for first order drugs… and (+/-) 10% for zero order drugs
What does the FDA classification of "A" or "B" indicate?
A=therapeutically equivalent… B=equivalence is doubtful
What is the main determinate of tissue distribution?
organ perfusion
Why is it that a response to a drug like thiopental terminates even though much of the drug remains in the body?
redistribution to lesser perfused areas of the body
What positive effects would a site-specific drug have?
enhance therapeutic value and limited toxic side effects
Name 4 drug reservoirs in the body
1. Fat (for lipid sol drugs), 2. GI tract, where extensive enterhepatic circulation increase levels of drug hours or days after administration… 3. Intracellular macromolecules (in liver and muscle store Drug for extended periods)… 4. Bone and teeth, i.e., tetracycline