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Anes. Pharm I Test 1
Pharmacokinetics & Pharmacodynamics concepts
| Question | Answer |
|---|---|
| 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
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