Module 4 - Case Study

Question 1

Stan was experiencing anemia (reduced RBC count), easy bruising/bleeding, loss of appetite, fever and signs of infection. Which drug, methotrexate or mercaptopurine caused these?

Answer 1

Both, the side effects overlap

Question 2

Which drug(s) are accounting for Stan’s worsening condition?

Answer 2

Side effects overlap between both drugs - we need to look into pharmacokinetics to uncover more

Question 3

What pharmacokinetic parameter indicates which drug is the culprit for Stan’s worsening condition?

Answer 3

Mercaptopurine (pro-drug) –> activated to become TGN
TGN is metabolized by TPMT
TPMT deficiency can lead to TGN accumulation, and life-threatening bone-marrow suppression

Question 4

What lab tests could be done to help the doctor?

Answer 4

Genetic tests to look for TPMT deficiency

Question 5

What would you suggest should be done to optimize drug therapy for Stan?

Answer 5

Reduce the dose, or stop giving mercaptopurine