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28 Cards in this Set
- Front
- Back
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In a graph depicting Velocity (V) vs. [Substrate] ([S]), When is Km=[S]
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at 1/2 Vmax
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What is Km?
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Reflects the affinity of the enzyme for its substrate
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If you decrease the Km, what happens to the substrate affinity?
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The substrate affinity will increase
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Competitive Inhibitor or Noncompetitive Inhibitor: Resembles substrate
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CI
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Competitive Inhibitor or Noncompetitive Inhibitor: Overcome by increasing [S]
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CI
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Competitive Inhibitor or Noncompetitive Inhibitor: Bind active site
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CI
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Competitive Inhibitor vs Noncompetitive Inhibitor: Effect on Vmax
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CI: Unchanged
NCI: decreases |
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Competitive Inhibitor vs Noncompetitive Inhibitor: Effect on Km
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CI: Increases
NCI: Unchanged |
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Formula for volume of distribution (Vd=...)
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Vd= Amount of drug in body/[plasma drug]
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Clearance (CL)=....=.....
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rate of elimination/[plasma concentration]
= Vd x Ke(elimination constant) |
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t1/2=
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0.7 x Vd/CL
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What is the concentration (% eliminatedl) at 1, 2, 3, and 4 half lives?
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50%, 75%, 87.5%, 93.75%
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How do you calculate a loading dose?
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Loading Dose = Cp x (Vd/F) where Cp=target plasma [drug], Vd=Volume of dist., and F=bioavailability
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How do you calculate a maintenance dose?
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=Cp x (Clearance/F), where Cp=target plasma [drug] and F=bioavailability
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What and how would you change the dosing (maintenance vs. loading) in a pt with impaired renal or hepatic fxn?
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Loading dose unchanged, maintenance dose decreases
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How do you speed up elimination of a drug (as in during overdose)?
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You give them something to cause the drug to go into it's ionized form.
Ionized molecules can be filtered but not readily reabsorbed so they will be more likely to pee it out If the drug is a weak acid ==> treat with bicarbonate (raise pH, make pee more basic) If the drug is a weak base ==> treat with ammonium chloride to lower the pH (make pee more acidic) |
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What are three examples of drugs with zero order elimination
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Phenytoin
Ethanol Aspirin |
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What are examples of drugs that are weak acids that might be overdosed?
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methotrexate
phenobarbital aspirin treat with bicarb to make them pee it out |
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What does the graph of Time vs. [plasma] look like in zero-order elimination? 1st order?
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zero - Line with a negative slope
1st - Negative curve w/ asymptote as it approaches a concentration of zero |
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What is a Phase 1 reaction?
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P-450 in liver causes reduction, oxidation, hydrolysis ==> slightly polar, water soluble metabolites that are often still active
this is what you loose with age |
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What is Efficacy? Potency?
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Efficacy - Maximal effect a drug can produce
Potency - Amount of drug needed for a given effect |
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What is a Phase 2 reaction?
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Acetylation, Glucuronidation and Sulfation yielding very polar, inactive metabolites that can be renally excreted
Elderly still have GAS. |
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In a plot of Agonist Dose vs. % of maximum effect, what effect does a competitive antagonist have on a sigmoidal curve generated by an agonist
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Shifts the curve to the right, decreasing potency and increasing EC50
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In a plot of Agonist Dose vs. % of maximum effect, what effect does a noncompetitive antagonist have on a sigmoidal curve generated by an agonist
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Limits the percent of maximum effect, decreasing efficacy
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How do you calculate the therapeutic index?
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LD50/ED50 (Lethal dose for 50%/Effective dose for 50%)
TILE= TI=Ld/Ed |
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The therapeutic index can be determined by LD50/ED50. What does this mean practically?
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Safer Drugs have a high TI value
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A drug has a very high TI value, What does that mean
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Very safe to use - low effective does and need lots of it to kill your patient
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A drug has a very low TI value. What does that mean?
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Very narrow range between benefiting your patient and killing him.
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