1CM Urinary Excretion

Question 1

How can you calculate AUC w/o using concentration and time points?

Answer 1

AUC = FD/KVd

• F = fraction of dose absorbed
• D = dose

Question 2

What is the relative availability for urinary excretion data?

Answer 2

Du infinity a / Du infinity b

- Du infinity = total amount in urine

Question 3

What is absolute availability?

Answer 3

(AUC po / dose po) / (AUC iv / dose iv) OR (Du infinity po / dose po) / (Du infinity iv / dose iv)

Question 4

What is the initial formula for what is happening in the urine?

Answer 4

dDu/dt = KeDb (Ke = urinary excretion rate)

Question 5

What are the problems w/ obtaining valid urinary excretion data?

Answer 5

• Significant fraction excreted unchanged
• Specific assay
• Frequent sampling
• Long sampling time
• Variations in pH and volume affects excretion rates
• Complete urine specimen required (empty bladder)

Question 6

For urinary excretion data, what does the y-intercept reflect?

Answer 6

The total amount of drug in the body you would administer in an injection multiplied by Ke (urinary elimination rate constant)

Question 7

Describe the t* method

Answer 7

1) Should be given time points and drug amount points
2) Make column of Du/t, but t points should be point 2 minus point 1
3) Do the division to get drug/time (ex: mg/hr)
4) Do column of t*, which is the midpoint between 2 time points

Question 8

Describe the sigma-minus method

Answer 8

1) Should be given time points and drug amount points
2) Make column of cumulative drug amounts
3) Make column of Du infinity minus Du (Du infinity = last point in cumulative data column, so this should leave you w/ 0 as the last point of this column)