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Question 1. Determine an intravenous loading dose of phenytoin sodium injection for UI, 5'8", 71 Kg male, using a volume of distribution of 0.65 L/Kg and a desired level of 23 mg/L. Round to the nearest multiple of 50 mg. (1 point)
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Question 2. Determine a daily maintenance dose of oral phenytoin sodium capsules for UI using a Vmax of 9.01 mg/kg/day, Km of 12.1 mg/L, Css = 14.6 mg/L. Round to the nearest dose using available phenytoin sodium capsules to determine a daily dose for UI. (1 point)
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Question 3. A 21 year-old, 6'1", 87 kg female had been receiving 350 mg phenytoin chewable tablets daily for 2 weeks and her trough plasma concentration was 7.75 mg/L. Her dose was increased to 250 mg twice a day and now two weeks later her phenytoin level is 17.3 mg/L. (3 x 0.5 points)
a. Calculate the patient-specific Km.
b. Calculate the patient-specific Vmax
c. Calculate the new maintenance daily dose of phenytoin chewable tablets with a desired Cpss of 15 mg/L using both patient-specific Vmax and Km.
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Question 4. A female patient with generalized tonic-clonic seizures attained a steady state serum concentration of 10 mg/L on 430 mg daily of Dilantin® kapseals. She was transferred to a rehabilitation hospital and received 500 mg Dilantin® kapseals. Two weeks later she as noted to have ataxia and a new level was 20 mg/L.
a. Calculate Km and Vmax using the graphical method of Mullen. (2 x 0.25 points)
b. Calculate the new dose per day to produce 15 mg/ml. (0.5 points)
c. Using the regression method of Ludden, determine Vmax and Km. (2 x 0.25 points)
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Equation 31.2.2 IBW for Female Patients
Equation 31.2.3 Vd for Obese Patients (i.e. Actual Body Weight > 120% of Ideal Body Weight)
Equation 31.2.4 Loading Dose
Equation 31.2.5 Dose Rate
Equation 31.2.6 Patient Specific Km
Equation 31.2.7 Patient Specific Vm
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