Pharmacokinetics Exam

10 marks

Question 1.

The first pass principle can be described as

  • a) The drug which is metabolized and excreted before it reaches systemic circulation
  • b) The drug which reaches the portal vein and passes through the liver
  • c) The drug which is metabolized by CYPs in the intestine and doesn’t reach circulation
  • d) Exhaling volatile and gaseous drugs

Question 2.

ABC efflux transporters reduce absorption of a drug and increase excretion of a drug.

  • True
  • False

Question 3.

A drug is metabolized by the body, where the bodies resources are in excess to metabolize the drug. However, we are assuming that distribution of the drug is instantaneous. If an IV bolus of 100 mg is given and the drug has a K el of .72, how long until the drug is at 25 mg?

  • a) 75 hours
  • b) .965 hour
  • c) 1.93 hours
  • d) 37.5 hours

Question 4.

The CYP3A4 is responsible for transforming this hypothetical prodrug, where the metabolite has a small therapeutic window. If a drug which acts as a inducer for CYP3A4 was taken concurrently with the hypothetical prodrug which was prescribed to reach therapeutic EC50, what would the expected effect of the prodrug metabolite be on the body.

  • a) No therapeutic effect
  • b) The prodrug metabolite could increase to a toxic level in the body
  • c) The prodrug metabolite will have no therapeutic effect since there will be no CYP3A4 to metabolize the drug
  • d) The log P of the prodrug will increase for the prodrug metabolite

Question 5.

Two people with different VNTRs in the CYP2D6 genetic coding region are administered the same dose of a drug. If person A is found to have a MR greater then person 2. If no other factors are at play, which one would be expected to be the extensive metabolizer and the other a poor metabolizer?

  • a) No difference
  • b) A is poor metabolizer, while b is extensive metabolizer
  • c) B is poor metabolizer, while a is extensive metabolizer

Question 6.

Which of the following is true for the absorption of a drug with a pKa of 4

  • a) It will be extensively metabolized by the body
  • b) It will be in its neutral form in the small intestine and hence be more readily absorbed
  • c) It will be less ionized in the stomach hence more readily absorbed
  • d) It’s pKa is to small for any reasonable amount of absorption hence its bioavailability will be to small for any therapeutic effect

Question 7.

The elimination rate is:

  • a) A hypothetical volume with which the drug occupies
  • b) Measured by the area under the curve for an intravenous dose/ the dose size
  • c) A more accurate representation of drug clearance
  • d) A fixed variable rate for a drug which depends on the drug concentration in plasma

Question 8.

A drug taken intravenously still experiences absorption, distribution, metabolism and elimination.

  • True
  • False

Question 9.

The first pass effect is not avoided if a drug is taken

  • a) orally
  • b) Intravenously
  • c) dermally
  • d) Via eye drops

Question 10.

A phase II drug metabolite is in the urine, however, this drug has a small therapeutic window so the clinician doesn’t want to risk accumulation. As such they prescribe sodium carbonate. This is because it:

  • a) Makes the urine acidic, therefore, the metabolite will be ionized and unable to reenter the body.
  • b) Makes the urine basic, therefore, the metabolite will be ionized and unable to reenter the body.
  • c) Turns the blood acidic, therefore, the metabolite is ionized so less can accumulate in tissue
  • d) Turns the blood basic, therefore, the metabolite is ionized so less can accumulate in tissue

Answers.

  1. a)
  2. True – ABC efflux transporters pump drug back into intestine limiting uptake, whilst they also pump metabolized polar drugs out of cells.
  3. c) t = ln(.25)/-k
  4. b)
  5. b)
  6. c)
  7. d)
  8. True – absorption is approximately 100%, still distributed, metabolized, excreted
  9. a) Passes through the liver
  10. b) – pH of blood is fixed, pH of urine is variable. pH>pKa means more drug in ionized form. Ionized form of drug can not cross cell barriers without help.

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