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home work 2
 
Homework II
 1. T. M. 70 kg female patient received IV injection of drug X. A urine samples 
have been collected as follows: 
Time Interval (hr)        Amount of drug in urine. (mg) 
   0 – 1                                9.7 
   1 – 2                                6.7 
   2 – 4                                6.2 
   4 – 6                                3.4 
   6 – 9                                1.5 
   9 - 12                               0.63 
 
Using the Rate method, determine the following: 
 a. The half-life for drug X. 
b. Elimination rate constant kd 
c. Renal elimination rate constant ke 
c. Fraction of the drug excreted unchanged renally 
Homework II
 2. The following data was obtained from a patient received IV bolus of dioxin 1 mg. 
Collection Time (hr)    Urine Volume (mL)   Conc. of digoxin in urine (mg/mL)   Plasma conc. of digoxin at T(midpoint) 
     1                     1000                       0.225                            1.6 
     2                     1200                       0.123                            1.04 
     3                     1400                       0.068                            0.68 
     4                     1100                       0.056                            0.44 
     5                     1300                       0.031                            0.29 
     7                     2500                       0.017                            0.15 
 
a. Graphically, determine the half-life of digoxin. 
b. Calculate the amount of digoxin remains in the body after four days. 
c. Calculate the Renal clearance CLR and the total body clearance CL of digoxin. 
d. Assuming that digoxin is only eliminated through kidney and liver. Calculate Km 
Homework II2
 3. Calculate the half life for Methotrexate in a patient weighting 70 kg, the 
volume of distribution of the drug is 0.4 L/kg and the renal clearance CLr is 3 
L/hr, assuming 95% of the drug is eliminated in the urine unchanged 
(unmetabolized). 
4. The half life of Penicillin in adult healthy patients is 30 minutes, the renal 
clearance Clr is 275 mL/min and its elimination is 90% through the kidney 
unmetabolized. What is the apparent volume of distribution for penicillin? 
 
 

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