WEBVTT
Kind: captions
Language: en
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Moving on to vancomycin.
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Here again I have a very brief case for vancomycin therapy.
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This patient has a case of pneumonia caused by MRSA.
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The MIC is greater than one minimum per
liter
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for this strain of Staphylococcus aureus.
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The physician wants to dose
vancomycin aggressively
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to achieve a peak concentration of 28 milligrams per liter
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and a trough concentration of 17 milligrams per liter.
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The patient has an estimated creatinine clearance of 60 ml/min
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and weighs 60 kilograms.
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Since the estimated creatinine chemist is 60
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so we know his renal function is
compromised nearly 50 percent.
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So here we have a series of question to ask
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What is the estimated K, elimination rate constant?
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What is the estimated volume of distribution?
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What is the clearance for vancomycin?
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What loading those would you recommend?
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And what would you recommend for dosing interval based on the half-life of the drug?
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And what maintenance dose would you
recommend to initiate the therapy?
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So vancomycin elimination here we have
two formulas based on the literature information
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which says K elimination rate constant is equal to
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0.00083 times creatinine clearance plus
0.0044 reciprocal hour
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The other formula from the patient
population
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is equal to creatinine clearance times 0.06
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and here we realize that creatinine
clearance can be calculated or estimated
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by Cockcroft-Gaultl equation or by MDRD equation
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based on serum creatinine.
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So calculation step number one.
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Applying the equation that we presented previously
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Here K is equal to 0.00083 times creatinine clearance
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which is sixty plus 0.0044
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and it turned out to be 0.0542 reciprocal hour.
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And since we are dealing
with first-order kinetics
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therefore half-life is 0.693 divided by K
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and that give us twelve point eight hours for half-life
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Calculation step number two
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clearance of the drug or vancomycin is equal to creatinine clearance times 0.06
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and that turned out to be three point six liter per hour.
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Step number three
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clearance is equal to KV
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and therefore volume of distribution V is equal to clearance divided by K.
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And that turned out to be
sixty six point four liter for vancomycin.
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Continue on to step four
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we want to calculate loading dose
and remember the definition of loading dose
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is the product of peak concentration
times volume distribution
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that is the dose that we want to apply
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in order to obtain a peak concentration as soon as possible
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So peak concentration desirable peak concentration is 28
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the volume of distribution is sixty six point four
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and that gives us a dose of 1859.2mg
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and of course we round it up to two thousand milligrams
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to be infused over one hour