PHAR 4634 Pharmaceutics III

Chapter 14 - 15

Homework Assignment - 1995 #5

1. Assuming a one compartment linear pharmacokinetic model, with kel = 0.19 hr-1 and V = 18.2 L, calculate the plasma concentration at 0.5, 1, 2, 4, 6, 9, 12, and 24 hours after 250 mg i.v. doses every 8 hours. Plot the data (as points) on linear and semi-log graph paper. Sketch a line reflecting the plasma concentration throughout each dosing interval.

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2. Assuming a one compartment linear pharmacokinetic model, with kel = 0.13 hr-1 and V = 21.4 L, calculate the plasma concentration at 0.5, 1, 2, 4, 6, 9, 12, and 24 hours after the following IV bolus dose schedule: 200 mg at time 0 hr; 150 mg at 6 hr; 250 mg at 18 hours. Plot the data (as points) on linear and semi-log graph paper. Sketch a line reflecting the plasma concentration throughout each dosing interval.

Answer

3. Calculate an appropriate dosing regimen for the following male patient; age = 56 years, weight = 79 kg, serum creatinine = 2.0 mg/ 100 ml (mg%). With this drug the kel is a function of creatinine clearance; kel = 0.04 hr-1 with CLCr = 20 ml/min and kel = 0.12 hr-1 with CLCr = 75 ml/min. Apparent volume of distribution is calculated as 0.28 L/kg. Develop a dosing regimen to keep the peak concentration close to but below 6 g/ml and the trough concentration below 1.0 g/ml.

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4. A drug is to be given orally every six hours to achieve an average concentration of 15 mg/L. Calculate the dose (F = 0.90) required if t1/2 = 11 hours and V = 23 L. Estimate the peak and trough concentrations after steady state is reached.

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