PHAR 4634 Fall 1995 Pharmaceutics III OU HSC College of Pharmacy

Second Semester Exam 10 November 1995

Section ONE. Sketch a Graph or Diagram - 4 x 4 = 16 points

Sketch the graphs or diagrams requested in the space provided. Make sure you carefully include any distinguishing characteristics. Include all labels and appropriate units. Assume that a linear one compartment model applies for each sketch unless otherwise specified.

Q 1.1 A linear graph of Cp versus time for three different dosage forms (A, B, and C). A and B have the same extent of absorption and rate of absorption whereas C has a slower absorption but similar extent of absorption

3" x 2.5" space for sketch

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Q 1.2 A linear plot of Cp versus time (for 72 hr) after three equal oral doses given at 0, 24, and 48 hours.

3" x 2.5" space for sketch

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Q 1.3 A linear Dettli plot with fe = 0.33.

3" x 2.5" space for sketch

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Q 1.4 A Scatchard plot representing 1:1 drug protein binding with one type of binding site. (Note: This question refers to material in Chapter 18)

3" x 2.5" space for sketch

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Section TWO. True/False Check the Correct Response - 10 x 2 = 20 points

Q 2.1 Considering the three transport processes (active, facilitated and passive), facilitated is the one process that is not saturable since no carrier is required. True False

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Q 2.2 The average plasma concentration calculated at steady state after a large number of uniform oral doses given with uniform dosing intervals is independent of the absorption rate constant. True False

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Q 2.3 Elimination of salicylate (a weak acid) is faster when the urine pH is 4.5 compared with when the urine pH is 8.5. True False

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Q 2.4 Phase II metabolism processes commonly result in metabolites that have a smaller molecular weight than the parent drug. True False

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Q 2.5 Increasing the amount or percentage of lubricant in a table formulation will generally increase the dissolution rate of the drug because of the penetrating capacity of these ingredients. True False

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Q 2.6 Drugs that are extensively distributed into specific tissue regions, such as chloroquine into the liver, tend to have quite small values for the apparent volume of distribution. (Note: This question refers to material in Chapter 18) True False

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Q 2.7 When the total intrinsic liver clearance of a drug is quite high compared with liver blood flow it may be said that the drug has flow limited clearance. True False

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Q 2.8 When developing a multiple dose regimen, doubling both the dosing interval and the dose will result in the same average plasma concentration. True False

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Q 2.9 With just oral data it is not possible to determine separate values of V and F. True False

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Q 2.10 Increasing the number of particles that make up a certain weight of drug will slow down the overall dissolution process because there are more particles to go into solution. True False

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Section THREE Short Answer 3 x 5 = 15 points

Remember to limit the time spent on this section to 5% of 80 minutes (= 4 minutes) per question.

Q 3.1 Briefly describe the intramuscular route of administration, giving advantages and disadvantages of the method.

6.5" x 2" space for sketch

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Q 3.2 Briefly describe the parameter clearance, providing a definition, an equation suitable for estimating this parameter, and units.

6.5" x 2" space for sketch

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Q 3.3 Briefly describe the parameters of Fick's first law as they relate to drug dissolution.

6.5" x 2" space for sketch

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Section FOUR Calculations 16 + 19 + 14 = 49 points

Show all your work for full credit. All material not deleted or crossed-out will be considered for grading.

Q 4.1 (16 points) Calculate a suitable dosage regimen for an 85 kg patient who is to be given drug X to achieve an average plasma concentration of 8 g/ml. The apparent volume of distribution for this drug is 1.9 L/kg and the half-life is 19 hours. The oral bioavailability is 75%. Calculate a once-a-day oral dose. Tablets are available containing 25, 100, and 250 mg. What would be a suitable regimen. Calculate average and minimum concentrations for your 'suitable' regimen.

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Q 4.2 (19 points) Calculate a suitable dosage regimen (MD and LD) for a 56 year old, 79 kg male patient with a serum creatinine of 1.8 mg/100 ml who requires a gentamicin peak close to but below 8 mg/L and a trough below 1 mg/L. [Use kel = 0.021 + (0.00275*Clcr) hr-1 and V = 0.21 L/kg]. Choose suitable rounded doses (nearest 10 mg) and a suitable interval. Check your final regimen.

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Q 4.3 (14 points) The following data were collected after the oral administration (200 mg) of a drug. Calculate ka, kel, and V/F using the method of residuals. Assume ka > kel. (2 - cycle semi-log graph paper provided)

Data Obtained After 200 mg Oral Administration
Time hr Concentration mg/L <-----> <-----> <----->
0.25 4.5


0.5 7.3


1 9.8


1.5 10.4


4 7.7


9 3.9


14 1.8


Answer

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