PHAR 7632 Homework #2 2001 - Answers

Curve Fitting and Laplace Exercise

Question 1. Graph the data below on semi-log graph paper.

The following data was collected after an I.V. bolus dose of 250 mg.

Time (hr) Cp (mg/L)
1 7.5
2 5.2
3 2.5
5 0.85
6 0.58

Note three cycle graph paper

Using Cp(0) = 13.3 mg/L and Cp(6) = 0.541 mg/L

kel = (ln(13.3) - ln(0.541)) / (6.0 - 0.0) = (2.59 - - 0.614) / 6 = 3.204/6 = 0.534 hr-1

Intercept = Cp(0) = 13.3 mg/L

V = Dose/Cp(0) = 250 / 13.3 = 18.8 L

Question 2. Analyse the same data using Boomer and parameter type 8.

Use Pre-exp value = 13.3 with 1.33 and 133 as upper and lower limit

Use Lambda value = 0.534 with 0.0534 and 5.34 as upper and lower limit

 ** FINAL OUTPUT FROM Boomer (v3.0) **      20-Feb-2001 ---  3:31:34 pm

 Title:  Homework #2                                                 
 Input: From HW0102.BAT                                                      
 Output:  To HW0102.OUT                                                      
 Data for Cp came from keyboard (or ?.BAT)                                             
 Fitting algorithm: Damping Gauss-Newton Method
 Weighting for Cp              by 1/Cp(Obs )^2                                      
 DT =   0.1000E-02     PC =   0.1000E-04 Loops =     2
 Damping =     1

                    ** FINAL PARAMETER VALUES ***

  #  Name                  Value       S.D.       C.V. %  Lower <-Limit-> Upper

  1) Pre-exp A              13.191       1.13       8.6       1.3      0.13E+03
  2) Lambda A              0.53383      0.223E-01   4.2      0.53E-01   5.3    

 AIC =   -13.0821     Final WSS =   0.328295E-01
               R-squared =   0.9991     Correlation Coeff =   0.9927    

 Model and Parameter Definition

  #  Name                    Value       Type From To     Dep  Start Stop

  1) Pre-exp A           =   13.19        8    0    1       0    0    0
  2) Lambda A            =  0.5338        9    0    0       0    0    0
  3) LagTime A           =  0.0000       10    0    0       0    0    0

 Data for Cp              :-

 DATA #   Time       Calculated     Observed      (Weight)   Weighted residual

     1   0.0000       13.1911      0.000000      0.000000      0.000000    
     2    1.000       7.73468       7.50000      0.133333     -0.312913E-01
     3    2.000       4.53529       5.20000      0.192308      0.127828    
     4    3.000       2.65930       2.50000      0.400000     -0.637214E-01
     5    5.000      0.914310      0.850000       1.17647     -0.756583E-01
     6    6.000      0.536112      0.580000       1.72414      0.756682E-01

     WSS for data set  1 =   0.3283E-01
               R-squared =   0.9991     Correlation Coeff =   0.9927    

 Maximum value for Cp              is      7.5000     at       1.000    

 Calculation of AUC and AUMC based on trapezoidal rule

 AUC and AUMC for Cp              using Observed data

       Time         Concentration      AUC             AUMC

     0.000000        0.000000    
      1.00000         7.50000         10.3455         3.75000    
      2.00000         5.20000         16.6955         12.7000    
      3.00000         2.50000         20.5455         21.6500    
      5.00000        0.850000         23.8955         33.4000    
      6.00000        0.580000         24.6105         37.2650    
                                      25.6970         45.8193    

 MRT =      1.7831    

 Calculation of AUC and AUMC using Method 9 of R.D. Purves

 AUC and AUMC for Cp              using Observed data

       Time         Concentration      AUC             AUMC

     0.000000        0.000000    
      1.00000         7.50000    
      2.00000         5.20000         11.7333         13.4667    
      3.00000         2.50000         15.4200         22.4603    
      5.00000        0.850000         18.4789         34.1564    
      6.00000        0.580000         19.1854         38.0193    
                                      20.2719         46.5736    

 MRT =      2.2975    

Plots of observed (*) and calculated values (+)
           versus time for Cp             . Superimposed points (X)

    13.19      Linear                      13.19      Semi-log
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   0.0000                                 0.5361    
 0              <-->             6.0     0              <-->             6.0    
 Plot of Std Wtd Residuals (X)         Plot of Std Wtd  Residuals (X)
   versus time for Cp                    versus calcd Cp(i) for Cp             

    1.411                                  1.411    
 |            X                          |           X                         
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 0X====================================  0====================================X
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  -0.8351                                -0.8351    
     0.00       <-->             6.0         0.54       <-->             13.    

.BAT as binhexed (Mac) or zipped (Win) files.

Question 3. Use Laplace transform method to integrate the differential equation for Component 2 in the diagram below.

[-------------]       [-------------]      [------------] 
[             ]  k1   [             ]  k2  [            ]
[ Component 1 ] ----> [ Component 2 ] ---> [ Component 3]
[             ]       [             ]      [            ]
[-------------]       [-------------]      [------------] 

The dose is put into Component 1 and k1 and k2 are first order rate constants.

dX(1)/dt = - k1 x X(1)

dX(2)/dt = k1 x X(1) - k2 x X(2)

dX(3)/dt = k2 x X(2)

Take the Laplace of each equations

s x L(X(1)) - X(1)(0) = - k1 x L(X(1))

s x L(X(2)) - X(2)(0) = k1 x L(X(1)) - k2 x L(X(2))

s x L(X(3)) - X(3(0) = k2 x L(X(2))

Since X(1)(0) = Dose, X(2)(0) = 0, and X(3)(0) = 0

s x L(X(1)) + k1 x L(X(1)) = Dose

s x L(X(2)) + k2 x L(X(2)) = k1 x L(X(1))

s x L(X(3)) = k2 x L(X(2))

the first equation gives L(X(1)) = Dose / (s + k1)

the second equation gives L(X(2)) = k1 x L(X(1)) / (s + k2)

substituting the first (for L(X(1))) into the second gives:

L(X(2)) = k1 x Dose / ((s + k2) x (s + k1))

the third equation gives L(X(3)) = k2 x L(X(2))/s

substituting the first (for L(X(2))) into the third gives:

L(X(3)) = k1 x k2 x Dose / (s x (s+k1) x (s+k2))

with A = k1 x k2 x Dose, a = k1 and b = k2

Using Laplace table gives:

A x (1/(a x b) + exp(-a x t)/(a x (a-b)) - exp(-b x t)/b x (a-b))

or

X(3) = k1 x k2 x Dose x (1/(k1 x k2) + exp(-k1 x t)/(k1 x (k1-k2)) - exp(-k2 x t)/k2 x (k1-k2))