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Anes. Pharm I Test 1

Pharmacokinetics & Pharmacodynamics concepts

QuestionAnswer
What is pharmacokinetics? the body's effect on the drug
What are the four linked processes of pharmacokinetics? absorption, distribution, biotransformation (metabolism) and excretion
What is absorption (bioavailability)? the extent to which a drug reaches its effect site after its introduction into the circulatory system
What is distribution of ionized drugs? They are water soluble, but poorly lipid soluble so they do not enter the CNS. Ionized drugs stay mainly in the plasma.
What is the distribution of non-ionized drugs? They are lipid soluble, so they diffuse easily across lipid barriers like the blood brain barrier, placental barrier
What is biotransformation (metabolism)? The chemical process by which the drug molecule is altered in the body. The key is to make everything water soluble so kidneys can excrete it.
What does phase I of metabolism consist of? oxidation, reduction and hydrolysis - these increase the drugs polarity and prepare for Phase II
What does Phase II of metabolism consist of? conjugation
What is conjugation? drug or metabolites are covalently liked to a highly ionized molecule and the resulting conjugate is more water soluble for excretion
What is excretion? renal and hepatic clearance is the rate of elimination of a drug from the body via the urine or the bile
What is elimination 1/2 life? the time for the drug in the body to decrease by 50%
What effects the elimination 1/2 life? volume of distribution and changes in clearance
What is elimination 1/2 time? the time for the plasma concentration of the drug to decrease to 50% during the elimination phase
What is context sensitive 1/2 time? the time for the plasma drug concentration to decrease by 50% after discontinuing a continuous infusion of specific duration
Which drug does not have a high context sensitive 1/2 time? propofol
What is effect site equilibration time and when is it important to consider? how long it takes the drug to actually start working. Important to consider for re-dosing intervals.
What is s drug's mechanism of action? how the drug works
Typically, the longer the duration of the infusion.... the longer the context sensitive halftime
What is pharmacodynamics? the drug's effect on the body
What is therapeutic dose? the amount of a medication required to produce the desired effect. lethal dose/effective dose
What is toxic dose? the minimal dose required to produce an adverse effect
What is effective dose? a dose of pharmacologic agent which will have a therapeutic effect
What are the two compartments of the Two Compartment Model? Central compartment (VRG) and peripheral compartment (vessel poor groups: muscle, fat, bone)
What parts of the body belong to the Vessel Rich Group (VRG)? intravascular fluid (plasma), highly vascular areas of brain, heart, lungs, liver, kidneys
How much of the cardiac output does the vessel rich group (VRG) receive? 75%
How much of the cardiac output do the vessel poor groups receive? 25%
What are the phases of the Two Compartment Model? distribution phase (alpha) and elimination phase (beta)
What is volume of distribution? relates the amount of drug in body to serum concentration
Volume of distribution in inversely proportional to what? protein binding
Define hyperreactive smaller than normal dose in drug produces intended effect
Define hypersensitive an exaggerated, immune mediated response to a drug
Define hyporeactive larger than normal dose is needed to produce intended effect
Tolerance usually results from what? chronic exposure to drug
Define tachyphylaxis very rapid development of tolerance, frequently seen with acute administration
Additive effect 1 + 1 = 2
Synergistic Effect 1 + 1 = 3
What two drugs are an example of a synergistic effect? fentanyl and versed
Potentiation 1 + 0 = 3
Define agonist a substance that binds to a specific receptor and triggers a specific response
Agonists mimic the action of what? an endogenous ligand like a hormone or neurotransmitter; the agonist binds to the same receptor
Define antagonist a drug that has affinity for a receptor but no efficacy; it blocks effect
Which commonly has a higher affinity for the given receptor: the agonist or the antagonist? antagonist
Define full agonist causes maximal activation of all receptors
Define partial agonist binds to receptor but causes a smaller effect at a full dosage than a full agonist
What is competitive antagonism? a reversible effect of an antagonist on a receptor that can be overcome by increasing agonist concentration
What is non competitive antagonism? an irreversible effect that cannot be overcome by increasing the agonist concentration - new receptors must be made
What is physiologic antagonism? two agonist drugs that bind to different receptors and cause opposite effects
The simultaneous activation of an alpha agonist causing vasodilation and a beta agonist causing vasoconstriction is an example of what? physiologic antagonism; the actions of the two agonist cancel each other out
What is chemical antagonism? one drug binds with another and makes it inactive; no receptor activity is involved
Protamine and heparin are an example of what? chemical antagonism
What is affinity? the degree of drug to receptor interaction for a given drug
What can be described as the attraction between a drug and a receptor? affinity
What is efficacy? the drug's ability to produce the desired response expected by stimulation of a given receptor
What does the Spare Receptor Concept explain? how maximal or nearly maximal response can often be produced by activation of only a fraction of the receptors present
Chronic exposure to agonists causes the body to increase or decrease the number of receptors for this agonist? Decrease the number of receptors
What is the decreasing of receptors due to chronic exposure of an agonist called? down regulation
With down regulation(desensitization), will a person require an increased or decreased amount of that drug to produce the same effect as in a normal person? Increased
Chronic exposure to opioids causes... down regulation
What does chronic exposure to antagonists cause? up regulation
In up regulation, are receptor numbers increased or decreased? increased
If patient on beta blocker therapy forgets to take medication before surgery, what would happen if he or she were exposed to beta stimulation and why? enormous, exaggerated response to stimulation due to up regulation of receptors
Created by: Mary Beth